soil management · 2014-02-17 · maintaining soil structure and soil organic matter, reducing soil...

SOIL MANAGEMENTA GUIDE FOR TASMANIAN FARMERS

DEPARTMENT ofPRIMARY INDUSTRIES,

WATER and ENVIRONMENT

Andrew Hamlet

2002

Soil Management — A Guide for Tasmanian Farmers.

Published by the Department of Primary Industries, Water and EnvironmentPrinted by Regal Press, Launceston, Tasmania

© Copyright 2002

ISBN 0 7246 6742 3

Refer to this report as:Hamlet A.G (Ed) 2002, Soil Management — A Guide for Tasmanian Farmers. First Edition, Department ofPrimary Industries, Water and Environment, Tasmania, Australia

DISCLAIMERThis document outlines soil management guidelines for Tasmanian farmers. The Department of PrimaryIndustries, Water and Environment (DPIWE) and the Tasmanian Farmers and Graziers Association (TFGA)accepts no responsibility for any application of this information.

The information is believed to be accurate and reliable but no warranty to this effect is given. No liability isaccepted by the DPIWE, TFGA, their employees, nor any other person for any claim which may arise fromany person using the information in the document.

Where information from other authorities has been provided, the data is included and used in the formprovided by others. The responsibility for the accuracy of the information does not reside with DPIWE orTFGA.

This document is not exhaustive. It is an overview. Professional advice should be sought for interpretationof legislation and guidelines where required.

ACKNOWLEDGEMENTSThe Tasmanian Farmers and Graziers Association and the Department of Primary Industries, Water andEnvironment would like to acknowledge the following:• Natural Heritage Trust for their support in the development of the project• Farmers involved in the meetings that took place at or near Forest, Sisters Creek, Riana, Gawler,

Kindred, Sassafras, Cressy, Pipers River, Scottsdale, Nile, Fingal, Swansea, Ross, Richmond, Hamilton,Furneaux Group and King Island

• Members of Agricultural Consultants Tasmania• Members of the steering committee• DPIWE research, extension and policy officers

PREFACE

Agriculture is a major contributor to the State's economy and will remain sowell into the future. Tasmanian agriculture depends on its soil, water andvegetation resources for on-going sustainable crop and animal production.Consequently, Tasmanian farmers need to protect the resources that theyrely on by adopting environmentally sound soil management practices.

Soil management practices continue to improve on many Tasmanian farms.However, instances of unsustainable soil management practices remain. Asingle inappropriate action has the potential to cause permanent soildegradation.

As a comprehensive, yet simple to read, set of recommended soilmanagement practices these guidelines will greatly assist in improving soilmanagement practices in Tasmania.

By adopting or maintaining improved soil management practices, farmerswill be better placed to gain opportunities to sustain production and attainmarketing advantages. They should also be in a better position to meet theirenvironmental obligations.

By acknowledging and supporting the adoption of improved soilmanagement practices, contractors and processing companies, who sharein the duty of soil management with farmers, will also share in the benefits.

This is not a set of rules and regulations. It is a user-friendly blueprint thatfarmers can consult as a guide to improving their soil managementtechniques - and therefore increasing or at least sustaining their returns.

Our soil is often an undervalued asset but there is a growing understandingof the range of techniques needed to prevent deterioration. We are thereforeconfident that farmers will welcome this important initiative.

Kem Perkins OAM David Llewellyn MHAPresident TFGA Minister for Primary Industries,

Water and Environment

INTRODUCTION

These guidelines have been prepared as part of a joint Department of PrimaryIndustries, Water and Environment – Tasmanian Farmers & Graziers Associationproject funded through the National Heritage Trust. The project is a response to theneed for a comprehensive, yet simple to read, set of recommended soil managementpractices for both cropping and grazing.

Due to the diversity of Tasmanian soils and farming practices, these guidelines arenot prescriptive or applicable to all circumstances. Alternative ways to improve soilmanagement practices can be developed.

The guidelines provide farmers with a set of management practices to address theissues of soil and water quality protection. Guidelines have been outlined formaintaining soil structure and soil organic matter, reducing soil erosion, managingsalinity, avoiding soil contamination, managing riparian land and planning aneffective soil management strategy.

Farmers, contractors and processing companies share in the duty of soilmanagement. Therefore, guidelines for contractors and processing companies areincluded as an integral part of planning an effective soil management strategy.

A major component of the development of these guidelines has involved anextensive consultation process. Farmer groups were consulted at or near Forest,Sisters Creek, Riana, Gawler, Kindred, Sassafras, Cressy, Pipers River, Scottsdale,Nile, Fingal, Swansea, Ross, Richmond, Hamilton, Furneaux Group and King Island.The document was positively received by each farmer group.

It is not the purpose of this document to extensively repeat information from otherdocuments. The document provides a summary of present information andpractices, in accordance with other relevant documents. References and contactsthat provide further detailed information are listed where appropriate.

This document is not designed to be read from cover to cover. It is organised to allowthe user to consult specific recommendations and information relevant to the on-farmsituation.

As principles and current best practices may change over time due to improvementsin technology, this document is to be reviewed and updated when deemed necessaryby farmers or regulators.

INDEXPage

CHAPTER 1 PLANNING 11.1 Know your soils and land capability 21.2 Develop a Whole Farm Plan 41.3 Work with contractors and processing companies 5

CHAPTER 2 MAINTAINING SOIL STRUCTURE AND SOIL ORGANIC MATTER 72.1 Maintain vigorous root growth 82.2 Incorporate stubble and green manure crops into soil 102.3 Manage a flexible grazing system 122.4 Use appropriate implements 142.5 Manage soil moisture levels 162.6 Manage traffic and tillage, especially on wet soils 182.7 Repair soil that is already compacted 20

CHAPTER 3 REDUCING SOIL EROSION 233.1 Control run-on and run-off 243.2 Minimise wind erosion, sheet erosion and rill erosion 263.3 Treat gully erosion, tunnel erosion and mass movement 283.4 Manage dispersive soils 29

CHAPTER 4 MANAGING SOIL SALINITY 314.1 Assess the situation 324.2 Avoid salt accumulation when irrigating 334.3 Improve drainage 344.4 Increase vegetation cover 35

CHAPTER 5 AVOIDING SOIL CONTAMINATION 375.1 Manage fertiliser and chemical applications 385.2 Minimise the impact of soil acidification 405.3 Prevent disease, pest and weed invasion 41

CHAPTER 6 MANAGING RIPARIAN LAND 436.1 Manage stock 446.2 Manage native vegetation 466.3 Minimise the impact of run-off into streams 47

GLOSSARY 48

REFERENCES / CONTACTS 50

CHAPTER 1

PLANNING

This chapter discusses requirements for planning aneffective soil management strategy. The followingstrategies are recommended:• know your soils and land capability;• develop a Whole Farm Plan;• work with contractors and processing companies.

Using land capability units as a basis for a Whole Farm Plan, farmers will be better able to match theirmanagement practices with the ability of the soil to support those practices. Farmers that work withcontractors and processing companies are more likely to maintain their strategy to improve soilmanagement on their property.

Page 1

DPIWE contact details are listed at the end of this document

1.1 Know your soils and land capability

Knowledge of the land capability on your farmprovides the basis for effective planning andsustainable soil management practices. Landcapability assessment provides a ranking of theability of an area to support a range of agriculturalactivities on a sustainable basis.

Knowing your soil

Assessment of land capability requires knowledgeof soil types on your farm. The following is asummary of the main soil types used for cropping:• Black cracking clays have a black, well

structured, swelling clay overlying a mottledbrown to greyish-brown clay. Mainly occurringin the Midlands and south-east Tasmania;

• Cressy soils have a dark grey-brown/brownloam/clay-loam topsoil overlying a red-brown/grey-brown clay. Scattered betweenCressy and Westbury;

• Deep sands consist of deep uniform sands,with topsoils ranging from red-brown to grey-brown. Occasionally occurring along the northcoast, the Midlands and in south-eastTasmania;

• Duplex soils have a distinct texture contrastbetween topsoil and sub-soil. Mainly occurringin the Midlands and south-east Tasmania,scattered along the east coast, Meander Valleyand Derwent Valley;

• Ferrosols (Krasnozems) are red-brown/red,strongly structured, gradational, clay-loam/claysoils that generally become darker, more acidicand higher in organic matter further inland.Occurring in the north-west and to a lesserextent in the north-east.

The DPIWE booklet “Managing Tasmania’sCropping Soils” provides detailed information onTasmanian soil types that are used for cropping.Further details of tests, recommendations andcase studies relating to the management of eachsoil type are included. The booklet is availablefrom DPIWE and via the DPIWE website.

Soil maps

Soil maps can provide information on soil typesand their distribution. These maps are available tothe public through the Service Tasmania Shopfrontand the LIST website (www.thelist.tas.gov.au).

While half of the agricultural land in Tasmania hasbeen mapped, the reliability of this informationvaries across the state. The scale of some of thesemaps may not be appropriate for use at the farmscale.

Guidelines• Be aware of the distribution of soil types on your farm• Conduct field assessments and use soil maps to clarify soil distributions.• Define land capability units according to features such as soil type, erosion

hazards and climatic hazards.• With the aid of a Whole Farm Plan, match soil management practices to

identified land capability units.

A soil map super-imposed onto an aerial photograph.Initials indicate soil types. Yellow lines represent soilboundaries and red lines represent roads.

Land capability units

Land capability units are a sub-division of thelandscape according to various soil features.Similar land capability units require the same levelof management and are capable of the same levelof productivity. Many of the land capabilityboundaries will be obvious, but others require fieldchecking.

The Tasmanian land capability classificationsystem is based on soil type, slope and climate.The classification system comprises sevenclasses ranked in order of increasing degrees oflimitation in relation to agricultural use andagricultural versatility. Therefore, Class 1 is thebest (most versatile) land and Class 7 the poorest.An important assumption during assessment isthat a better than average level of management isbeing applied to the land.

Some of the major constraints to agricultural useof land in Tasmania include:• shallow soil depth;• coarse rock fragments;• poor drainage;• uneven or unreliable rainfall distribution;• erosion hazard (based on soil texture,

structure, dispersion and slope characteristics);• salinity hazard;• frost, flood or wind hazards.

Grose (1999) provides detailed guidelinesregarding the classification of agricultural land inTasmania. Contact DPIWE about this publicationand other information about the Tasmanian landcapability classification system.

Matching soil practices to land capability

Land capability units provide the basis for planningappropriate management of agricultural land. Byunderstanding the variations and limitations ofland capability on the property level, farmers arebetter able to plan for appropriate soilmanagement practices. See Section 1.2 for furtherinformation about developing a Whole Farm Plan.

Class 3 land on basalt. Positive factors include soiltype and climate. The slope is a negative factor.

Class 3 land on tertiary sediments. Poor drainage isthe main negative factor.


1.2 Develop a Whole Farm Plan

FarmBis co-ordinator in DPIWE for furtherinformation.

A record of responsible management

Adherence to an effective Whole Farm Planprovides a record of responsible landmanagement. Farmers using this documentationas a Quality Assurance system are better placedfor potential market advantages.

Computer software is available for planning andrecording farm operations and outcomes to satisfyquality standards.

FarmBis can provide further information aboutdefining quality standards and monitoringmanagement practices. Contact a FarmBis co-ordinator in DPIWE for further information.

Guidelines• Use land capability units as a basis for developing an effective Whole Farm

Plan.• Use aerial photographs to produce a basic Whole Farm Plan.• Use computer software to produce a more sophisticated Whole Farm Plan.• Where possible, attend a Whole Farm Planning course.• Use a farm plan as documentation of responsible land management.

Whole farm planning is an on-going process thatchanges and adapts according to newtechnologies and practices. A Whole Farm Plancan present farmers with opportunities to integratefinancial stability with improved soil management.

Using land capability units as a basis for a WholeFarm Plan, farmers will be better able to matchtheir management practices with the ability of thesoil to support those practices. See Section 1.1 forfurther information about assessing soil types andland capability units on your farm.

An integral part of farm planning requires thatfarmers work with contractors and processingcompanies. See Section 1.3 for furtherinformation.

Mapping

An aerial photograph (scale ranging from 1:2500to 1:5000) can provide the basis for mapping andmatching permanent features with land capabilityunits.

Improved mapping information can be obtainedfrom computer software packages. These rangefrom simple calculation packages to complexpackages that work with Global PositioningSystems, aerial maps or satellite images.

Attending a course

A Whole Farm Planning course trains farmers todevelop effective farm plans. Farm planningcourses are organised by a range of services. TheFarm Business Improvement Scheme (FarmBis)currently provides support for farmers toparticipate in management training. Contact a A manually produced Whole Farm Plan.

1.3 Work with contractors and processing companies

Contractors and processing companies

The duty of soil management extends tocontractors and processing companies.Recommended practices for contractors andprocessing companies include:• encouraging and supporting the adoption of

sustainable soil management practices byfarmers;

• providing adequate advance notice to farmersbefore arriving on their farms, so that farmerscan take steps (where possible) to minimisethe potential impact from proposed operations;

• consulting each farmer to recognise theirpersonal requirements for managing their landin a sustainable manner;

• conducting activities that at least meet thestandards for managing land in a sustainablemanner;

• using appropriate implements. See Section 2.4for further information;

• managing traffic, especially on wet soil. SeeSection 2.6 for further information;

• managing fertiliser and chemical applications.See Section 5.1 for further information;

• preventing disease, pest and weed invasion.See Section 5.3 for further information.

By acknowledging and supporting the adoption ofappropriate soil management practices,contractors and processing companies will gainopportunities to sustain production, improve theircollective image and attain marketing advantagesfor their produce.

Guidelines• Work with contractors and processing companies so that they recognise your

personal requirements for managing land in a sustainable manner.• Favour contractors and processing companies that encourage and support the

adoption of sustainable soil management practices.• Favour contractors and processing companies that conduct activities that at

least meet the standards for managing land in a sustainable manner.• Favour contractors and processing companies that are licenced through their

improved soil management practices.

Farmers, contractors and processing companiesshare in the duty of soil management. Therefore,an integral part of planning a soil managementstrategy requires improved interaction betweeneach of these stakeholders.

Farmers

The principle recommendation for farmers is tofavour and work with contractors and processingcompanies that are licenced through theirimproved soil management practices. Farmersinteracting with contractors and processingcompanies are more likely to maintain theirstrategy to improve soil management.

By working with licenced contractors andprocessing companies, farmers are better able toplan for appropriate soil management practices.See Section 1.2 for further information aboutdeveloping a Whole Farm Plan.

CHAPTER 2

MAINTAINING SOILSTRUCTURE AND SOIL

ORGANIC MATTER

This chapter discusses requirements to maintain soilstructure and soil organic matter. The following strategiesare recommended: • maintain vigorous root growth;• incorporate stubble and green manure crops into soil;• manage a flexible grazing system;• use appropriate implements;• manage soil moisture levels;• manage traffic and tillage, especially on wet soils;• repair soil that is already compacted.

Soil structure is defined as the way in which soil particles and the pore spaces between them are arranged.Soil with good structure tends to have a high proportion of stable aggregates (ranging from 2 to 10 mm insize) with many interconnected and resilient pores. This allows for improved plant productivity as a result ofenhanced aeration, infiltration and drainage and increased activity of beneficial soil organisms. It also allowsfor improved root growth to access water and nutrients.

Degraded soil has a high proportion of small particles and few water stable aggregates. The reduction ofpore size and continuity results in massive blocks that restrict root growth and plant productivity. Compactedsoil requires more cultivation to prepare a seedbed and this additional cultivation causes furtherdeterioration in soil structure. A surface crust may develop that prevents seedlings emerging and reducesinfiltration of water.

Organic matter contributes to improved soil structure and reduces the risk of compaction by binding soilparticles into stable aggregates. Organic matter also contributes to an improved capacity for the soil to retainnutrients, retain moisture and support a greater population of beneficial soil organisms. Such organismsinclude bacteria, fungi, earthworms, ants, dung beetles and slaters.

In turn, beneficial soil organisms help to maintain soil organic matter turnover and nutrient cycling. Soilstructure is improved when thread-like fungal growths and mucus coverings of soil organisms help toproduce soil aggregates.


2.1 Maintain vigorous root growth

Green manure crops

If long-term pasture is not possible, a greenmanure crop is recommended between croppingphases. Longer growing seasons for greenmanure crops mean greater benefits to the soil.

Green manure crops that produce rapid rootgrowth include short rotation ryegrass and oats.

Lupins or tick beans are useful for producingorganic matter that is high in nitrogen. The highnitrogen content in legume residues alsostimulates biological activity to improve the rate ofnutrient cycling.

Further information is available in the DPIWEleaflet “Green Manure Crops — a Powerful SoilManagement Tool”.

Guidelines• For a long-term pasture phase, sow perennial pasture.• Manage grazing of pastures to ensure optimum root growth.• Between cropping phases, sow green manure crops.• Conduct soil tests and seek professional interpretations to determine the

optimum fertiliser requirements for vigorous plant growth.• Apply the appropriate type and rate of fertiliser evenly and with precision

Vigorous root growth improves soil structure,increases soil organic matter levels and providesprotection from erosion.

Pasture

Through vigorous root growth, a well-managedperennial pasture phase can improve both soilstructure and soil organic matter levels. These soilbenefits are greatest when the pasture phase (androot development) exceeds 2 years.

An effectively managed grazing system canimprove pasture and root growth and therebyimprove soil organic matter, soil structure andstock performance. See Section 2.3 for furtherinformation about managing a flexible grazingsystem.

Vigorous pasture.

Green manure crops (lupins and oats).

Matching fertiliser applications to plantrequirements

Fertiliser applications need to be matched to therequirements for vigorous root growth. Too littlefertiliser results in poor plant growth, while toomuch fertiliser is economically wasteful and canlead to soil contamination. See Section 5.1 forfurther information about managing fertiliserapplications so as to avoid soil contamination.


2.2 Incorporate stubble and green manure crops into soil

Stubble and green manure crops that have setseed contain high amounts of woody tissue andlow amounts of nutrients. This slows their rate ofincorporation and decomposition into the soil.

Stubble requires suitable temperatures andmoisture to allow for effective decomposition of thehigh amounts of dry woody tissue. Depending onthese conditions, effective stubble decompositionmay range from several months to several years.

Incorporation of stubble is not always necessary.Some crops (such as cereals and peas) can bedirect drilled through a layer of chopped stubble onthe soil surface.

Grazing and baling

High amounts of stubble and green manure cropcan be utilised through baling and effectivegrazing. If baling, a larger amount of organicresidues can be removed by harvesting closer tothe soil surface. Note that the removal ofexcessive quantities of crop material that is highlyalkaline can increase the risk of soil acidification.For further information, see Section 5.2 aboutmanaging soil acidification and Section 2.3 aboutmanaging a flexible grazing system.

Although burning can effectively remove stubble,organic residues are lost to the atmosphere ratherthan being recycled through grazing or baling. Ifstubble can be effectively managed throughgrazing and baling, then burning is notrecommended.

Guidelines• Slash and mulch stubble and green manure crops to improve incorporation.• Consider spraying short rotation ryegrass and oats with herbicide to improve

incorporation.• Where necessary, graze or bale stubble and green manure crops to reduce the

amount to be incorporated.• Avoid burning stubble if it can be effectively managed through practices

described above.• Avoid excessive cultivation.

Incorporation and subsequent decomposition ofstubble and green manure crops into the soilimproves soil structure and soil organic matterlevels.

However, high amounts of green manure crops orstubble can be difficult to incorporate into the soil.Inadequate incorporation of organic residues intosoil can result in ineffective decomposition. In suchcases, improvements to soil structure and soilorganic matter levels are minimal. High amountsof organic residues can also hinder cultivationoperations and increase the risk of pests anddiseases.

Incorporating

Slashing and mulching stubble and green manurecrops can improve their subsequent incorporationinto the soil.

For some green manure crops, herbicide sprayingapproximately 3 weeks before ploughing allows forimproved incorporation into the soil. For example,short rotation ryegrass and oats can be sprayedoff in July before setting seed.

Green manure crops that are incorporated at thebeginning of their flowering phase offer thegreatest benefits to soil structure and soil organicmatter. This stage of growth provides the bestcombination of quality and quantity for improvedincorporation and decomposition rates.

Avoiding excessive cultivation

Excessive cultivation results in a rapid decline insoil structure and soil organic matter levels.Biological activity also declines as a result ofphysical injury to beneficial soil organisms and soilorganic matter decline. Therefore, minimal tillagepractices are generally recommended. However, amore intensive level of cultivation may be requiredperhaps once in every 5 years to provide a breakin disease, pest and weed cycles. See Section 2.4for further information about choosing appropriateimplements.

Incorporating stubble into soil.

Incorporating lupins into soil.

Slashing lupins.


2.3 Manage a flexible grazing system

To maintain animal and pasture performance, agrazing system needs to be flexible in accordancewith different soil moisture conditions. Appropriatestrategies during dry, wet and optimal conditionsare described below. Detailed information aboutgrazing systems is available from relevant agri-businesses and DPIWE.

Guidelines• Implement and monitor a flexible and effective grazing system to match

stocking intensity with pasture production.• For dry conditions, implement a well-managed combination of rotational

grazing and set stocking.• If most paddocks are not susceptible to pugging in wet conditions, implement

a well-managed combination of rotational grazing and set stocking.• If many paddocks are susceptible to pugging in wet conditions, implement a

well-managed set stocking system.• Rejuvenate damaged or sacrificed paddocks with a new pasture in the

following season.

Soil structure and soil organic matter levels can beseverely degraded through inappropriate grazingor over-grazing. Subsequently, stock performancedeclines and the risk of soil erosion is increased.

Poor management of set stocking also results inthe transfer of nutrients away from the grazingareas. As a result of stock camping, thesenutrients are deposited into small areas. Suchconcentrations result in poor nutrient recycling andincreasing the risk of soil and water contamination.

Maintaining an effective grazing system

An effectively managed grazing system canimprove pasture growth and thereby improve soilorganic matter, soil structure and stockperformance. Well-developed pasture cover androot growth increase productivity while alsoimproving water and nutrient cycling. Improvedmanagement of grazing patterns reduces theopportunities for stock camping, thereby improvingnutrient redistribution.

A grazing system is only effective if the stockingdensity is matched to the carrying capacity of eachpaddock. Planning and constant monitoring isessential to ensure that there is sufficient pasturein each paddock:• before grazing to allow for pasture resilience

during and after grazing;• during grazing to maintain animal performance;• after grazing to allow for rapid plant recovery.

A well-managed grazing system.

Grazing in dry conditions

In dry conditions, pasture growth is slow and theability of pasture to recover following grazing islow. Over-stocking in dry conditions may lead todegradation and exposure of soil through grazingand pulverisation of the soil surface.

A well-managed combination of rotational grazingand set stocking can avoid soil and pasturedegradation in dry conditions. For the rotationalgrazing system, the pasture recovery period andthe number of paddocks determine the grazingperiod in each paddock. Reducing the stockintensity can slow the rate of paddock rotation.

In conjunction with a rotational grazing system,sacrificing one or two paddocks with set stockingwill help to maintain a sufficient pasture recoveryperiod for the remaining paddocks. Sacrificedpaddocks need to be rejuvenated with a newpasture in the following season.

Grazing in wet conditions

Poor grazing management in wet conditions maylead to pugging of soil. This results in soilcompaction and pasture decline.

A rotational grazing system is not recommended ifthe majority of available paddocks are susceptibleto pugging. In this situation, well-managed setstocking strategies can reduce the incidence ofpugging.

If there are enough dry paddocks available, a well-managed combination of rotational grazing andset stocking can avoid soil and pasturedegradation in wet conditions. The pasturerecovery period and the number of paddocksdetermine the grazing period in each paddock.

Sacrificing one or two paddocks with set stockinghelps to maintain a sufficient pasture recoveryperiod for the remaining paddocks used forrotational grazing. Sacrificed paddocks need to berejuvenated with a new pasture in the followingseason.

Some strategies to reduce the incidence ofpugging include:• using pug-prone paddocks early in the winter-

feed plan;• using the driest paddocks in the wettest period

of winter;• allocating lighter stock in wetter paddocks, and

heavier stock in drier paddocks;• reducing stock intensity to better match pasture

production;• improving drainage to reduce the incidence of

waterlogging. See Section 2.5 for furtherinformation about managing soil moisturelevels.

Further information about managing grazing in wetsoils is available in the DPIWE leaflet “Managingwet soils on dairy farms”.

Grazing in optimal conditions

When soil is friable (not too wet and not too dry),pasture growth rates are potentially optimal. Thismay result in insufficient stocking densities tomaintain frequent paddock rotations. Highamounts of pasture can be managed throughincreased stocking densities and/or baling.


2.4 Use appropriate implements

Increased temperatures promote biological activityin the soil, thereby playing a major role in thesuccess of direct drilling. Compared to a springsowing, an autumn sowing extends the length ofthe growing season and utilises the remainingwarmth and friable soil conditions before the onsetof winter conditions.

Where very wet winter conditions are prevalent,sowing in winter may result in reduced yieldscompared to yields produced through conventionaltillage. Incidence of slugs and plant diseases canalso increase in wet conditions.

Tined implements

Compared to powered implements, tinedimplements cause less disruption to soil structure.Changing tine configurations and reducing stubblelength can allow easier flow of stubble throughcultivation machinery.

Powered implements

The use of powered implements (such as rotaryhoes and power harrows) tends to degrade soilstructure and soil organic matter throughpulverisation and smearing.

An exception to this general case applies tokrasnozem (ferrosol) soils. For such soils thathave a suitable moisture content and a high levelof stubble, less soil compaction will result fromeffective use of powered implements (at a suitablylow speed) compared to over-use of tinedimplements. In this instance, soil structure is bettermaintained from only one pass using poweredimplements, compared to the required two or morepasses using tined implements.

Guidelines• Choose implements that avoid excessive cultivation.• Be aware that inappropriate use of powered implements and mouldboard

ploughs will cause severe soil degradation.• Combine cultivation practices to reduce the number of passes.• Overcome machinery blockages by managing stubble and green manure

crops.

Any form of tillage results in a decline in soilstructure and soil organic matter. Excessivecultivation results in a rapid decline in soil organicmatter and beneficial soil organisms. Therefore,use of implements appropriate to soil conditions isessential.

Appropriate implements loosen the surface soilwithout unnecessary soil shattering, soil smearingand exposure of soil organic matter. The choice ofimplements depends on the soil to be cultivated,the soil moisture content, the amount of stubble inthe soil and the intended crop. Extensiveinformation of the use of appropriate implements iscompiled in the DPIWE booklet “ManagingTasmania’s Cropping Soils. The booklet isavailable from DPIWE and via the DPIWE website.

Effective management of stubble and greenmanure crops can allow for reduced machineryblockages and reduced power requirementsduring cultivation. See Section 2.2 for furtherinformation about incorporating stubble and greenmanure crops into soil.

Direct drilling

Direct drilling into crop residues improves soilorganic matter levels and minimises the risk oferosion. Successful direct drilling requires skilledand attentive operators and specifically designedmachinery.

For heavy soils, a combination of direct drilling andminimal surface tillage is necessary to allow forgood plant growth. For lighter soils, surface tillageis unnecessary. Direct drilling is especiallybeneficial for duplex soils (to minimise disturbanceof less fertile sub-soil) and deep sands (tomaintain the fragile soil structure).

Mouldboard ploughs

Mouldboard ploughing inverts surface soil and hasthe capacity to bury high amounts of residues. Forsoils with deep and friable topsoil such askrasnozems (ferrosols), mouldboard ploughing isquicker and more effective for maintaining soilstructure and reducing the risk of erosion,compared to tines.

Severe soil degradation can occur if mouldboardploughs are applied too deeply on shallow orsandy soil. This can result in the exposure of lessfertile (and perhaps more erodible) sub-soil. Forshallow duplex soils, no more than the upper 100to 150 mm of topsoil should be inverted.

There are cases where the incorporation of theunderlying clay sub-soil crust with the topsoil hasimproved wetting characteristics and thereby plantproductivity. However, such practices have a highrisk of failure and therefore prior professionaladvice is recommended.

A direct drill with trailing press wheels

A direct drill with a trailing roller.


2.5 Manage soil moisture levels

Grassed waterways are most applicable for cropand short-rotation pasture on sloping paddocks.Grassed waterways transport water along naturaldrainage lines. Grassed irrigator runs can help totransport water into grassed waterways. Graded(contour) drains help to transport water intograssed irrigator runs and grassed waterways.Refer to “Keeping your Soil on your farm” forfurther information about these drainage systems.

Cut-off drains, in conjunction with grassedwaterways, effectively divert water flowing towardsa paddock or a cultivated area. Installing cut-offdrains located along farm tracks or fence linesminimise interference to farming operations. Referto the DPIWE booklet “Managing Tasmania’sCropping Soils” (available from DPIWE and via theDPIWE website) and “Keeping your Soil on yourFarm” for further information about cut-off drains.

Hump and hollow drains are most applicable forpasture and crops on flat or poorly drainedpaddocks. The parallel ridges drain water toshallow waterways so that the root zone iselevated from the watertable. Refer the “DrainageInformation Package” for further information. Thispackage is available at DPIWE and via the DPIWEwebsite.

Guidelines• Seek professional advice before implementing drainage or irrigation systems.• Consider drainage systems that are easily incorporated into farming

operations.• Provide adequate drainage outlets that are directed away from neighbouring

properties.• Install appropriate surface and/or sub-surface drainage systems.• If irrigating, monitor soil moisture levels so as to match water requirements of

plants.• Improve uniformity of spray applications by avoiding irrigation in windy

conditions.• Adjust nozzles to optimise spray droplet size.• Use pressure-regulating devices to maintain a consistent sprinkler output.

Effective management of soil moisture can reducethe degree and extent of wet soil conditions in apaddock. A soil with appropriate moistureconditions offers improvements in plant growth,cultivation and vehicle access.

Drainage

Soil moisture levels can be managed throughimproved drainage systems. Extensive informationfor managing drainage is available from relevantagri-businesses and DPIWE.

Professional advice and surveying isrecommended for the correct positioning andgrading of major drainage systems. Consultationwith relevant neighbours and local authorities isalso recommended when planning drainageworks. Redirection of water may need approvalbefore commencing drainage work.

Where possible, it is recommended that drainageoutflows are directed towards settling ponds,dams or buffer strips to minimise sediment andnutrient run-off flowing into streams. See Section6.3 for further information about buffer strips.

Drains in dispersive soils can lead to soil instabilityand severe erosion. See Section 3.4 for furtherinformation about managing dispersive soils.

Raised beds with adjoining furrow drains are mostapplicable in continuous cropping systems, wherelivestock are excluded from the cropping area andwhere the gradient is no greater than 3%.Shortening the length of beds can reduce the riskof erosion resulting from high volumes of waterflowing along the furrows. Further informationabout raised beds is available from DPIWE.

Sub-surface drains are most applicable forpasture and crops where soil is permeable. Referto the “Drainage Information Package” for furtherinformation. This package is available fromDPIWE and via the DPIWE website.

Irrigation

To avoid applying too little or too much irrigationwater, applications need to be matched to plantrequirements. Monitoring soil moisture conditionsprovides information about required applicationrates and application scheduling. See Section 4.2for information about irrigating on saline soils.

Although useful indicators, tensiometers merelyindicate when plants are water-stressed, ratherthan indicating the level of soil moisture. Electricalreadings from capacitance probes can betterindicate soil moisture levels. Irrigation schedulingservices are available from a number ofagricultural support businesses. Furtherinformation about monitoring and scheduling ofirrigation is available through relevant agri-businesses or DPIWE.

A graded drain leading to a grassed irrigator run.

A cut-off drain

A grassed waterway linked with grassed irrigator runsin the foreground.

Hump and hollow drains.


2.6 Manage traffic and tillage, especially on wet

operation is done in exact relation to a previousor future operation. Automated guidance andsteering systems further enhance precision;

• reduced seeding, fertiliser and spray overlap.

Raised bed systems with adjoining furrow drainsare an advanced application of controlled trafficprinciples. This system is most effective incontinuous cropping systems, where livestock areexcluded from the cropping area and where thegradient is no greater than 3%.

Shortening the length of beds can reduce the risk of

soilsGuidelines• Avoid excessive cultivation.• Use appropriate cultivation equipment.• Manage soil moisture conditions through improved drainage and irrigation

systems.• Use controlled traffic systems (such as raised beds) to restrict traffic to

designated areas.• Manage stock movement and stock grazing through an effective grazing

system.• Before cultivation, assess the risk of soil compaction.• If tillage on wet soil is unavoidable, restrict operations as much as possible.• When possible, postpone operations until the soil moisture level is

appropriate.• Reduce axle loads in conjunction

with wider tyres and lower tyrepressure.

Excessive cultivation causes a decline of soilstructure and soil organic matter levels. In wetconditions, the risk of compaction increases as aresult of traffic and tillage. In very dry conditions,soil aggregates can be pulverised as a result ofcultivation.

Effective management of soil moisture conditionscan reduce the degree and extent of wet soilconditions in a paddock. See Section 2.5 for furtherinformation about managing soil moisture levelsthrough improved drainage and irrigation systems.

Restricting the impact of traffic

Controlled traffic systems (such as raised beds)restrict all heavy traffic to the same permanentwheel tracks. Subsequent benefits include:• reduced incidence of wet soil conditions,

thereby increasing opportunities to cultivate atthe appropriate soil moisture;

• elimination of soil compaction in the croppedarea, allowing for improved yields per hectaredespite the loss of cropping land frompermanent wheel tracks;

• reduced tractor power requirements as a resultof improved soil structure;

• increased precision of operations, so that each erosion resulting from high volumes of water flowing

along the furrows. Cut-off drains incorporated withinraised bed systems can divert drainage beforeaccumulating along the furrows. Further informationabout raised beds is available from DPIWE.Cropping with raised beds.

The simplest controlled traffic system involves therestriction of traffic to tracks and designatedheadlands. Managing stock movement can furtherreduce the impact of grazing. See Section 2.3 forfurther information about managing a flexiblegrazing system.

Minimising the impact of tillage

For non-sandy soils, the appropriate soil moisturecontent for cultivation is indicated when the soilcontains enough water to be friable but not somuch as to be plastic. Moist lumps of soil break offeasily by hand when the soil is in this ideal friablestate for safe cultivation.

The ‘hand-roll’ test for soil workability (also knownas the ‘soil-wire’ test) is a simple check todetermine the risk of compaction duringcultivation. The test does not apply to sandysoils.

The hand-roll test involves the followingprocedure:• digging to the depth of the cultivation layer;• taking a handful of soil from different levels;• working the soil to an even consistency;• attempting to form a sausage about 3 mm

round by rolling the sample between yourpalms.

When the soil is too wet for tillage, a 3mm thick rodwill easily form. This indicates that operationsneed to be delayed to avoid soil compaction. At theoptimum moisture content the soil rod will crackand break into short lengths. If the samplecrumbles the soil conditions are still suitable forcultivation. However, power requirements and soilshatter will be high.

The DPIWE booklet “Managing Tasmania’sCropping Soils” provides a detailed diagnosis ofthe risk of soil compaction for a range ofTasmanian soil types. The booklet is availablefrom DPIWE and via the DPIWE website.

In conjunction with the hand-roll test, a risk of soilcompaction can be indicated if boots leave a treadin the soil. Another indication may be soil adheringto wheels and equipment. However, significantcompaction might occur before this indicator isapparent.

Choice of implements appropriate to the soilmoisture conditions is essential. See Section 2.4for further information about using appropriateimplements.


2.7 Repair soil that is already compacted

The depth of the compaction layer determines thedepth of a ripping operation. Ripping to a depthgreater than 300 mm is only beneficial in deepsandy soils where wheel traffic has produced adeep compaction layer.

Compaction layers in clays tend to occur at muchshallower depths. Ripping between a depth of 200and 250 mm is recommended for such soils.

As the tines move through the soil, soil shatteringoccurs above a critical depth, while smearing andcompaction occurs below this critical depth.Therefore, ripping below the compacted layer (butnot below the critical depth) is required toeffectively shatter the soil. As the level is largelydetermined by soil moisture content, critical depthis constantly changing.

Effective ripping also requires that soil conditionsare friable (not too wet or too dry). Ripping wet soilcan be ineffective due to inadequate shattering ofthe compacted layer. Ripping dry soil requires ahigher power input to effectively shatter thecompacted layer. See Section 2.6 for informationabout assessing the risk of soil compaction.

Stabilising rip lines

Rip lines can be stabilised by avoiding trafficdirectly above the fractured soil. Vigorous rootgrowth can also help to stabilise rip lines. SeeSection 2.1 for further information aboutmaintaining vigorous root growth.

For dispersive sub-soil, gypsum (calciumsulphate) applied into rip lines can help to reducethe level of dispersion. See Section 3.4 for furtherinformation about managing dispersive soils.

Guidelines• Recognise signs of compaction, and determine its extent and depth.• Only rip if the operation effectively shatters a compacted layer and improves

drainage.• Don’t repeat ripping if earlier ripping is ineffective.• Immediately following ripping, stabilise rip lines.

Compacted soil is characterised by the presenceof layers in the profile with fewer pores, fewerindividual aggregates and fewer plant roots andearthworm channels. Soil that is not compactedhas a more friable soil structure.

Compaction may not be obvious at the surface asit can develop below the plough layer. Indicationsof a sub-surface compaction layer can include:• reduced plant growth resulting from restricted

root growth, poor drainage and poor aeration;• prolonged rainwater ponding on the soil

surface;• increased difficulty in cultivating.

Examination of an exposed profile can help toidentify signs of compaction and the depth atwhich compaction may occur.

Effective deep ripping

It is recommended that farmers read the DPIWEleaflet “Guidelines for Deep Ripping Soils” beforeproceeding with deep ripping. This leaflet isavailable from DPIWE and via the DPIWE website.

Deep ripping is defined as the ripping of soil,deeply, with a tine or similar tool primarily to loosencompacted soil. Deep ripping is not a surfacetillage operation and therefore should not bringsub-soil to the surface. Ripping operations aremost effective with the use of correctly spacedwinged tines.

In grazed paddocks, deep ripping is often onlyrequired in clearly compacted areas, such asheadlands, tracks, and gateways — rather thanthe whole paddock. Compared to grazedpaddocks, cropped paddocks may require morewidespread ripping because traffic compactiontends to be more evenly distributed.

Cultivated soil with poor structure

Cultivated soil with good structure

Winged ripper tines.

CHAPTER 3

REDUCING SOIL EROSION

This chapter discusses recommendations to reducethe risks of soil erosion by water and wind. Thefollowing practices are recommended:• control run-on and run-off• minimise wind erosion, sheet erosion and rill

erosion• treat tunnel erosion, gully erosion and mass

movement• manage dispersive soils

Soil on steep paddocks has a high potential to erode. A millimetre of soil eroded is the same as trucking 10to 15 tonnes per hectare and dumping it elsewhere.

The rate of soil erosion depends on climate (precipitation and wind), topography (angle and length of slope),soil properties (soil texture, soil structure and organic matter), vegetation cover and management. Climate,slope angle and certain physical characteristics of the soil cannot be directly controlled. However, theireffects may be modified indirectly through improved management practices.

Dispersive soil refers to soils affected by an excess of sodium ions attached to clay particles. Whendispersive soils are wet, clay particles repel each other and this causes the soil to disperse and becomeextremely susceptible to erosion.


3.1 Control run-on and run-off

Controlling run-on with cut-off drains

Cut-off drains, in conjunction with grassedwaterways, effectively divert water flowing towardsa paddock or a cultivated area. Installing cut-offdrains located along farm tracks or fence lines willhelp to minimise interference to farmingoperations.

Refer to the DPIWE booklet “ManagingTasmania’s Cropping Soils (available from DPIWEand via the DPIWE website) and “Keeping yourSoil on your Farm” for further information aboutcut-off drains.

Managing run-off with mulched-rip lines

Mulched-rip lines are most applicable for annualcrops on sloping paddocks. Rather than drainingrun-off, this system allows for increased infiltrationof water into the soil, thereby improving sub-soilmoisture levels and reducing the need for othersurface drains.

Single rip lines installed at regular intervals alongcontours slow surface run-off and reduce thelength of slope. The application of cereal strawalong the top of each rip line further improvesinfiltration and reduces run-off speed.

Mulched-rip lines offer minimal restrictions tofarming operations, and are cheaply and readilyinstalled. Contact DPIWE for further informationabout mulched-rip lines.

Guidelines• To intercept run-on, install cut-off drains across the top of each paddock.• To manage run-off, install systems that drain surface water flowing across

each paddock.• Provide adequate drainage outlets that are directed away from neighbouring

properties.• Assess the potential risks of erosion from a drainage system.• Consider drainage systems that are easily incorporated into farming

operations.• Seek professional advice to determine the correct positioning of drainage

systems.

Run-on is the flow of surface water from up-slopeonto a paddock that can lead to erosion. Run-onusually originates from roads, culverts, yards andadjacent paddocks.

Run-off is the flow of surface water over a paddockthat can lead to erosion. The risk of erosion isincreased when volumes of surface wateraccumulate across a paddock.

Effective drainage systems minimise the potentialfor erosion by collecting and discharging surfacewater in an appropriate manner. Where possible, itis recommended that drainage outflows aredirected towards settling ponds, dams or bufferstrips to minimise sediment and nutrient run-offflowing into streams. See Section 6.3 for furtherinformation about buffer strips.

Seeking advice

Professional advice and surveying isrecommended for the correct positioning andgrading of major drainage systems, as overlysteep or narrow drains increase the risk ofscouring the drain itself. Extensive information formanaging drainage is available from relevant agri-businesses and DPIWE.

Consultation with relevant neighbours and localauthorities is also recommended when planningdrainage works. Redirection of water may needapproval before commencing any drainage work.

Drains in dispersive soils can lead to soil instabilityand severe erosion. See Section 3.4 for furtherinformation about managing dispersive soils.

Managing run-off with grassed waterways

Grassed waterways are most applicable for cropand short-rotation pasture on sloping paddocks.Grassed waterways transport water along naturaldrainage lines.

Grassed irrigator runs and cut-off drains can helpto transport water into grassed waterways. Graded(contour) drains can help to transport water intograssed irrigator runs and grassed waterways.

Broad and shallow drains are more easilyincorporated into farm operations as they areeasily slashed, easy to cross with machinery, andless susceptible to erosion. Refer to “Keeping yourSoil on your farm” for further information aboutthese drainage systems.

Managing run-off with raised beds

Raised beds with adjoining furrow drains are mostapplicable for continuous cropping systems, wherelivestock are excluded from the cropping area andwhere the gradient is no greater than 3%.

Shortening the length of beds can reduce the riskof erosion resulting from high volumes of waterflowing along the furrows. Cut-off drainsincorporated within raised bed systems can divertdrainage before accumulating along the furrows.Further information about raised beds is availablefrom DPIWE.

Managing run-off with hump and hollowdrains

Hump and hollow drains are most applicable forpasture on flat or poorly drained paddocks. Theparallel ridges drain water to shallow waterways,so that root zones are elevated from thewatertable.

Refer the Drainage Information Package forfurther information. This package is available atDPIWE and via the DPIWE website.

A cut-off drain.

Grassed irrigator runs leading to a grassed waterway.

Mulched-rip lines.


3.2 Minimise wind erosion, sheet erosion and rill

Stubble cover

Cereal stubble can protect soil (before and aftersowing) from erosion. Effective stubblemanagement requires appropriate implements,such as direct drills. Drills specifically designed tohandle stubble interference can reduce theincidence of machinery blockages. To furtherovercome machinery blockages, stubble can bechopped into shorter lengths. See Section 2.4 forfurther information about direct drills and otherimplements.

Vegetation cover

Vegetation can lower the risk of erosion byproviding protection and resistance to surfacewater flows, winds at ground level and rainfallsplash. Through vigorous root growth, vegetationcan improve the rate of surface water infiltrationinto the soil and rapidly utilise this ground-waterrecharge. Improved water infiltration also meansreduced amounts of run-on and run-off.

Vigorous vegetation cover may require adequatedrainage and appropriate fertiliser applications.For further information, see Section 2.5 aboutappropriate drainage and Section 5.1 aboutmanaging fertiliser applications.

erosionGuidelines• Avoid excessive cultivation.• Protect soil by maintaining stubble or vegetation cover.• Use appropriate implements (such as direct drills) to maintain stubble

protection.• For long term soil protection, maintain perennial pasture.• Match stocking intensity to the requirement for vigorous pasture growth.• Between cropping phases, sow green manure crops.• Use cover crops to protect establishing cash crops.• Establish windbreaks in strategic locations to reduce wind speeds.• Try to avoid cultivation in very dry conditions to minimise wind erosion.• Maintain surface roughness (through discing or ridged rollers) to minimise

wind erosion.

• Control run-on and run-off.

Wind erosion occurs on dry and exposed soils.The resultant air-borne soil particles may causephysical injury to pastures and crops in a processknown as sandblasting.

Sheet erosion is the removal of a uniform thinlayer of soil resulting from flowing water. Rillerosion occurs from concentrations of flowingwater forming rills in the surface soil.

Wind, sheet, and rill erosion is collectively referredto in this section as “erosion”. More specificterminology is used where necessary.

Careful cultivation

Any form of tillage can result in erosion. Excessivecultivation increases the chances of erosion, aswell as degrading soil structure and soil organicmatter levels.

Appropriate implements can help to minimiseerosion by loosening the surface soil (withoutunnecessary soil shattering) and retaining organicresidues (such as stubble). The choice ofimplements depends on the soil to be cultivated,the soil moisture content, the amount of stubble inthe soil, and the intended crop.

Perennial pasture with vigorous root growth is along-term approach for protection from soilerosion. The potential benefits are greatest whenthe pasture phase exceeds 2 years. To avoid over-grazing, stocking intensity needs to be matchedwith pasture production. See Section 2.3 forfurther information about managing a flexiblegrazing system. Grazing is not recommendedwhere the risk of erosion increases as a result.

Green manure crops can provide soil protectionbetween cropping phases. Green manure cropsthat produce rapid root growth include shortrotation ryegrass and oats. Lupins and tick beansare also useful for producing organic matter that ishigh in nitrogen. Further information is available inthe DPIWE leaflet “Green Manure Crops — aPowerful Soil Management Tool”.

Cover crops can provide soil protection at thebeginning of a cropping phase. Cover crops alsoprovide protection to the cash crop from winddamage and sandblasting.

Competition (for soil moisture, nutrients and light)between the cash crop and the cover cropinevitably increases as both crops becomeestablished. It is therefore essential to spray thecover crop with a selective herbicide shortly aftersowing to allow the cash crop to maintain vigorousgrowth.

Where moisture and nutrients are inherently low inthe soil, the cover crop may require herbicidespraying before (or a few days after) sowing thecash crop. A cover crop sprayed with herbicidecontinues to provide soil protection while itgradually withers and dies.

Consult DPIWE and refer to the DPIWE booklet“Managing Tasmania’s Cropping Soils” (alsoavailable via the DPIWE website) for furtherinformation about cover crops.

Protective cover crop in onions.

Windbreak shelter

Windbreaks, commonly trees, can significantlylower wind speeds on the leeward side for adistance of approximately 10 times the tree height.This shelter effect:• protects crops and pastures from wind

damage;• reduces evaporation rates of plants and soil;• protects stock from cold winds;• shades stock from excessive heat radiation.

The extent of the shelter depends on windbreakpermeability and windbreak positioning in thelandscape. Windbreak orientation is determinedusing local knowledge of the general prevailingwind directions.

Correct choice of species, preparation andplanting techniques and on-going maintenanceare essential for successful tree establishment.Trees require fencing from stock. Contact DPIWEor local Landcare groups for further information.


3.3 Treat tunnel erosion, gully erosion and mass

Vegetation cover

Prevention of erosion is the cheapest and mosteffective form of management. Prevention ispossible by identifying areas at risk of erosion, andthen managing appropriately.

Vigorous and permanent vegetation can anchorsoil into place and lower soil moisture levelsthrough utilisation of ground water recharge.Recommended vegetation includes deep-rootingperennial grasses, shrubs and trees. Furtherinformation about revegetation is available fromDPIWE.

Fertiliser applications need to match therequirements for vigorous plant growth. SeeSection 5.1 for further information about managingfertiliser applications.

Where erosion is unlikely to be managed byvegetation alone, structural operations may berequired prior to revegetation. Seek professionaladvice before attempting treatment.

movementGuidelines• Fence and exclude grazing.• Where possible, maintain vigorous deep-rooted perennial vegetation.• Where erosion is unlikely to be managed by vegetation alone, implement

structural operations prior torevegetation.

• Seek professional advice beforeattempting to prevent or treaterosion.

Gully erosion is the result of deep channels beingformed from concentrations of flowing water.

Tunnel erosion occurs when water moves alongcracks in dispersive sub-soils, underneath a morestable surface layer (dispersive soil refers to soilsaffected by an excess of sodium ions attached toclay particles). The tunnels may enlarge andcause the topsoil to collapse, forming pot-holesand eventually a gully. Tunnel erosion most oftenoccurs in duplex soils.

Mass movement (also known as landslides or soilcreep) occurs if the weight of the water-soaked soilbecomes greater than the ability of the sub-soil tohold it. Landslips tend to occur on steep slopesthat have a distinct slip plane with high moisturelevels. Signs of historical landslips include cracksand terracing across slopes, bent tree trunks onsteep slopes, and bulges of soil on foot slopes.

Tunnel erosion, gully erosion and mass movementis collectively referred to in this section as“erosion”. More specific terminology is used wherenecessary.

The occurrence of erosion can often result in:• total loss of production in the affected area;• damage to fences, roads, buildings and

adjacent paddocks;• hazards to stock and to machinery operations;• prevention of access.

An example of gully erosion.

3.4 Manage dispersive soils

Gypsum applications applied into rip lines oraround sub-surface drains can stabilise exposeddispersive soil by replacing sodium ions withcalcium ions. Surface gypsum applications are oflittle value for unexposed dispersive sub-soils.

If minimal tillage practices are deemedappropriate, careful usage of tines or direct drillsare recommended to avoid exposure of dispersivesub-soil. See Section 2.4 for further informationabout using appropriate implements. Mouldboardploughs and powered implements are unsuitablefor such areas.

Vegetation cover

Stabilisation of areas with dispersive sub-soilsrequires permanent vegetation cover, such asperennial pasture, shrubs and trees. Grazing is notrecommended if the protective vegetation issusceptible to over-grazing. Such areas requirefencing and permanent exclusion from stock.

Where grazing continues to occur, grazingsystems and fertiliser applications need to matchthe requirements for vigorous pasture growth. SeeSection 2.3 for further information about managingan effective grazing system.

Guidelines• Assess the level of dispersion by conducting simple field tests or including a

dispersion test as part of a routine soil analysis.• Seek professional advice before considering any drainage or tillage

operations.• Only consider drainage and tillage if such operations do not risk the exposure

of dispersive sub-soil.• Maintain vigorous vegetation cover.

Dispersive soil refers to soils affected by anexcess of sodium ions attached to clay particles.Sodicity refers to a soil that is highly dispersive;where more than 10 to 15% of the clay’s negativecharge is dominated by sodium ions. Most sodicsoils in Tasmania are dispersive only in the sub-soil. Such soils are usually duplex soils or blackcracking clays.

When exposed dispersive soils are dry, a crustdevelops that prevents seedlings emergingthrough the surface. When dispersive soils arewet, clay particles repel each other and thiscauses the soil to disperse. Exposed dispersivesoil is therefore extremely susceptible to erosionby water.

Dispersive sub-soils are best managed bymaintaining the protective non-dispersive surfacesoil. Where erosion has already occurred, refer toSection 3.3 for treatment recommendations.Further information about the following practices isavailable from DPIWE.

Drainage and tillage

Inappropriate tillage and drainage systems canexpose dispersive sub-soil and lead to soilinstability and severe erosion. Where there is arisk of exposing dispersive sub-soil layers, tillageor drainage systems are generally notrecommended.

Shallow surface drains are only suitable providedthat the drainage system does not expose thedispersive sub-soil. Prior to commencement ofdrainage operations, seeking professional adviceand arranging laboratory soil tests isrecommended.

CHAPTER 4

MANAGING SOIL SALINITY

This chapter discusses requirements to manage soilsalinity. The following practices are recommended:• assess the situation• avoid salt accumulation when irrigating• improve drainage• increase vegetation cover

Salinity problems in Tasmania are presently not as severe or extensive as in other parts of Australia.However, there is a potential for future increases in soil salinity. The National Land and Water Audit hasreported that about 3% of agricultural land in Tasmania is salt affected. The Midlands, north-east Tasmaniaand the Furneaux Group contain 80% of the salt affected land in Tasmania.

When surface soils become saturated and excess water can access groundwater, it can cause a watertableto rise closer to the root zone. Once a watertable reaches approximately 2 metres below the soil surface,evaporation at the soil surface draws water upwards from the sub-soil in a process known as capillary rise.If salts are mobilised and carried to the soil surface through this process, salt concentrates near the rootzone. These salt concentrations may affect plant productivity.

The process of salinisation worsens with poorly managed drainage and irrigation practices and when deep-rooted native vegetation is replaced with shallow rooted pastures and annual crops.

Electrical conductivity (EC) is the potential of a material to conduct electricity. The ease with which anelectrical current passes through water is proportional to the salt concentration in the water. Therefore, ECis an indirect measure of soil salinity. EC is commonly expressed as deciSiemens per metre (dS/m). Astandardised method of measuring salinity is called “Electrical Conductivity in a Saturated Extract (Esat)”.Soil salinity can be rated as moderate (Where Esat is 4 to 8 dS/m), very high (8 to16 dS/m) and extreme(>16 dS/m).


4.1 Assess the situation

Monitoring groundwater levels

The presence and movement of groundwater isthe primary vehicle for transporting salts to the soilsurface. A better understanding of groundwaterlevels allows for improved management decisions.

Installation of shallow observation bores is thesimplest and cheapest means of monitoringgroundwater. Contact DPIWE for furtherinformation about installing bores.

Guidelines• Check for salinity indicator species.• Assess soil and water salinity levels (with field kits such as Saltpak).• Hire consultants to rapidly measure apparent salt storage distributions.• Install shallow observation bores to monitor groundwater levels.

Indicators of salinity

Changes in botanical composition and plantgrowth are a reflection of soil salinity. Low tomoderate salinity can be indicated by reductions inpasture and crop yield. High salinity ischaracterised by the presence of sea barley grassand buck’s horn plantain. The presence of waterbuttons and patches of bare soil indicate severesalinity.

Assessing salinity

The DPIWE Saltpak is a simple field test kit thatcan help farmers to identify, assess and managesaline soils and water. The kit consists of a hand-held conductivity meter and other equipment. Thereadings obtained from the conductivity meter canbe applied to the tolerance tables provided todetermine the most suitable crop and pasturespecies for the observed salinity conditions.

Although Saltpak provides a valuable field test forsalinity, more accurate results might be requiredfrom laboratory facilities. Improved accuracy ofsalinity readings is especially important for theassessment and management of irrigation onsaline soils. Contact DPIWE for further informationabout Saltpak and other options for salinity testing.

Services are available for rapidly measuringapparent salt storage distributions with the use ofspecialised meters. Further information aboutthese services is available through relevant agri-businesses and DPIWE.

Mapping of apparent salt storage across a paddock.The ‘cooler’ colours represent areas of lower salinitylevels. The ‘hotter’ colours represent areas of highersalinity levels.

4.2 Avoid salt accumulation when irrigating

Irrigation scheduling services are provided by anumber of agricultural support businesses. Furtherinformation about monitoring and scheduling ofirrigation is available through relevant agri-businesses and DPIWE.

Monotoring salt levels in irrigation water.

The consequences of applying saline irrigationwater on land can be severe. A megalitre ofirrigation water that has a salinity level of 1 dS/mwill deposit 640 kg of salt. Therefore, it is importantto know the amount of salt being applied throughirrigation applications. Prior to application, testingirrigation water for conductivity is recommended.See Section 4.1 for further information aboutmonitoring salt levels.

Improved drainage can improve leaching rates.See Section 4.3 for further information aboutimproving drainage in saline areas.

Irrigation with saline water is not recommended onclay sub-soils where drainage is insufficient toallow salts to leach away from the root zone.

Guidelines• Seek professional advice before developing an irrigation system.• Avoid irrigation where natural drainage is insufficient to leach salts from the

root zone.• When salts in the root zone are insufficient to affect plant productivity,

uniformly apply water at the precise level that matches plant requirements.• In regards to the previous recommendation, only apply a higher level of

irrigation to when salts have accumulated in the root zone and need to beflushed away.

• Regularly monitor soil moisture and salt levels and the level of salt in irrigationwater.

• Avoid irrigation if the salinity level in the water exceeds 0.8 dS/m.

Avoiding excessive irrigation applications

To avoid an excessive accumulation of salt in theroot zone as a consequence of irrigation, saltsmust be leached further down the soil profile bywater percolation. An event whereby waterpercolates down a soil profile is termed a leachingfraction.

Excessive leaching fractions can worsen theprocess of salinisation by causing the salinewatertable to rise closer to the root zone. Idealleaching fractions provide enough water to leachsalts away from the root zone, but not enoughwater to raise the watertable.

When rainfall provides a sufficient leachingfraction to leach salts away from the root zone,irrigation water can be applied at a level that issufficient for crop requirements but insufficient toproduce further leaching fractions. A heavierirrigation is only necessary if salts accumulate inthe root zone to a level that affects cropproductivity.

By monitoring the level of soil moisture, the level ofwater applied can be better matched to croprequirements while avoiding excessive leaching.Although tensiometers are useful indicators, theymerely indicate when plants are water-stressedrather than indicating the level of soil moisture.Electrical readings from capacitance probes canbetter indicate soil moisture levels.


4.3 Improve drainage

DPIWE and via the DPIWE website) and “Keepingyour Soil on your Farm” for further informationabout cut-off drains.

Drainage lines in saline areas can be stabilisedand maintained with fencing and vegetation cover.See Section 4.4 for further information aboutestablishing and maintaining appropriatevegetation cover.

Raised beds

Raised beds with adjoining furrow drains canimprove surface drainage and salt leaching. Raisedbeds are most applicable for continuous croppingsystems where the gradient is no greater than 3%.

Reducing the length of beds reduces the risk oferosion that can result from high volumes of waterflowing along the furrows. Cut-off drainsincorporated within raised bed systems can divertdrainage before accumulating along the furrows.Further information about raised beds is availablefrom DPIWE.

Sub-surface drains

Sub-surface drains can reduce waterlogging andincrease the leaching of salt. These drains consistof a network of perforated pipes buried about 1metre below the soil surface. The spacing of sub-surface drains depends on soil permeability andamount of drainage required.

Use of subsurface drainage in saline anddispersive soils may cause soil instabilityproblems. Use of gypsum before installing sub-surface drainage may prevent this. Seek advicebefore proceeding.

Guidelines• Seek professional advice before positioning and grading drains.• Avoid draining naturally occurring wetlands.• Use cut-off drains to divert and remove surface water.• Use raised beds to improve surface drainage and salt leaching.• Use sub-surface drains to reduce waterlogging.• Provide adequate drainage outlets that are directed away from neighbouring

properties.• Stabilise surface drains with fencing and vegetation cover.

In areas where salinity has been identified,adequate drainage is essential to divert or removeany excess water from waterlogged areas.Diversion or removal of excess water can allow forsuccessful leaching of salt from the root zone tolower levels in the soil profile.

Consultation with relevant neighbours and localauthorities is recommended when planningdrainage works. Redirection of water may needapproval before commencing any drainage work.

Some shallow wetlands in eastern and centralTasmania are naturally saline. Such wetlands maybe listed under the Ramsar Convention asinternationally important wetlands. The “Directoryof Important Wetlands in Australia” databaseidentifies such wetlands in Tasmania. Furtherinformation can be obtained from DPIWE or viathe Environment Australia website(www.ea.gov.au/water).

Detailed information about managing drainage insaline areas is available from relevant agri-businesses, DPIWE and the “Drainage InformationPackage” (available via the DPIWE website).

Drains in dispersive soils can lead to soil instabilityand severe erosion. See Section 3.4 for furtherinformation.

Cut-off drains

Cut-off drains can divert and remove surface waterthat would otherwise become groundwaterrecharge. Refer to the DPIWE booklet “ManagingTasmania’s Cropping Soils” (available from

4.4 Increase vegetation cover

A flexible grazing system can help to avoid loss ofvegetation cover through over-grazing. SeeSection 2.3 for further information about managinggrazing.

Vigorous plant growth requires adequate drainageand appropriate fertiliser applications. For furtherinformation, see Section 4.3 about drainageoptions and Section 5.1 about managing fertiliserapplications so as to avoid soil contamination.

Planting is recommended in spring. Winter rainswill have washed away some of the salt and springis when moisture and temperature levels allow forrapid growth. Contact DPIWE about further detailsfor pasture and tree establishment andmaintenance.

Guidelines• Reduce the risk of salinity occurring in the first place by maintaining vigorous

growth of perennial pasture and tree species.• Improve protection of remnant native vegetation.• Treat saline discharge areas by establishing perennial pasture and tree species

that are tolerant to salinity and waterlogging.• Further treat salinity by maintaining vigorous growth of perennial pasture and

tree species in recharge areas.• Apply effective vegetation establishment and maintenance techniques.• Exclude stock during the establishment phase.

Water percolating into the sub-soil can cause thewatertable (and possibly salts) to rise towards thesoil surface. Vegetation cover can reduce theamount of water entering the watertable byutilising available soil water and surface water.Establishing appropriate vegetation cover requiresknowledge of discharge and recharges areas on aproperty level.

Recharge areas occur where surface water soaksthrough the soil surface. Following rainfall, all landhas the potential to act as a recharge area.Vegetation that can utilise large amounts of rainwhere it falls can prevent excess water soakingthrough the soil surface. Vigorous perennialpasture and/or deep rooting lucerne and trees isrecommended.

Discharge areas occur where the watertable isclose enough to the soil surface to evaporate,allowing for salts to accumulate. It also occurswhen groundwater flows out onto the soil surfaceas springs or seepages. These areas aregenerally located in depressions, drainage linesand saline seeps. The choice of ground cover fordischarge sites is limited by those species that aretolerant of salinity and waterlogging.

A mixture of deep-rooted winter-active perennialspecies is recommended for discharge areas.Puccinellia and tall fescue can grow well inextremely saline conditions. Strawberry clover andryegrass can grow well in low to moderately salinesoils.

CHAPTER 5

AVOIDING SOIL CONTAMINATION

This chapter discusses requirements to avoid soilcontamination and thereby help to maintain soilfertility. The following strategies are recommended foravoiding soil contamination:• manage fertiliser and chemical applications• minimise the impact of soil acidification• prevent disease, pest and weed invasion

A contaminant has undesirable effects on soil and water quality if its concentration exceeds a certainthreshold.


5.1 Manage fertiliser and chemical

provide guidance for improved productmanagement.

Accreditation

ChemCert Australia has developed anaccreditation program for farm chemical users.The program provides training in integrated pestmanagement, legislation, record keeping, productlabels, farm chemical formulations, environmentaland personal safety, application of crop protectionproducts and veterinary products. Accreditationalso allows farm chemical users to demonstratetheir capacity to manage chemical applicationssafely and effectively.

ChemCert accreditation is based on endorsedindustry competency standards conforming to thenational industry training standard for chemicalrisk management. This ensures farm chemicalusers comply with the legislation requirements forchemical use, occupational health and safety andenvironmental protection. Re-accreditation isrequired every 5 years to keep up-to-date withchemical usage and safety issue.

To enrol for ChemCert (Tas) Inc. contact theTasmanian Rural Industries Training Board

applicationsGuidelines• Become an accredited farm chemical user.• Favour operators that are licenced farm chemical users.• Apply the appropriate product at the appropriate rate and location. • Conduct regular soil tests and seek professional interpretations.• Avoid chemicals that may be toxic to a subsequent crop.• Avoid mixing or using products near drainage lines, streams or rivers.• Avoid applications in imminently windy or rainy conditions.• Favour products that are target specific with minimal residue periods.• Reduce applications of phosphate fertilisers containing cadmium impurities.• Carefully manage the application of effluent and sewage sludge (biosolids).• Ensure appropriate storage, usage and disposal of chemicals.

• Prepare emergency procedures incase of chemical leaks or spills.

Poor management of applications is economicallywasteful and may deposit residues that take yearsto break down. Excessive applications can alsolead to contamination through run-off and leachinginto waterways.

Elements that are harmful to plants or reduceyields if they are present in high concentrationsinclude zinc, copper, nickel, cadmium and arsenic.Elements that are potentially harmful to animalsand people include lead, arsenic, cadmium,mercury, copper, fluorine, selenuim andmolybdenum.

By precisely matching appropriate applications toplant requirements, the risk of contamination isminimised. There are a number of documents that

(TRITB) on phone (0363 312131), fax (0363314344) or email ([email protected]).

The Australian Fertiliser Services Association(AFSA) has developed a code of practice andaccreditation program (Fertcare) for its members.This program is a self-regulatory program withinthe fertiliser services industry to promote a moreprofessional service from the fertiliser industry.

AFSA can be contacted by phone (03 5381 2870),fax (03 5383 3745), email ([email protected]) and the internet(www.afsa.net.au).

Guidelines and codes of practice

There are Codes of Practice that are endorsedand published in Tasmania by the Agricultural,Silvicultural and Veterinary Chemicals Council.The codes regard aerial spraying, ground sprayingand the supply and use of veterinary chemicalproducts. These publications are available atDPIWE and via the DPIWE website.

The DPIWE “Guidelines for Interpreting Labels”provides advice for the interpretation ofagricultural chemical product labels. The DPIWEChemcollect guidelines and Drum-musterguidelines provide information for appropriate

storage, handling and disposal of chemicalcontainers. Further information is available atDPIWE and via the DPIWE website.

Avoiding cadmium contamination

Cadmium accumulation in the soil can beminimised by avoiding phosphate fertiliserscontaining cadmium impurities. Soil organic matterreduces plant uptake of cadmium alreadyoccurring in the soil. Further information aboutcadmium contamination is available from DPIWE.

Managing biosolid and effluentapplications

Biosolids that contain unacceptable quantities ofpotential contaminants are not suitable forapplication, regardless of any potential agriculturalbenefit.

The following publications are available at DPIWEor via the DPIWE website.

The “Tasmanian Biosolids Reuse Guidelines”provides advice for the safe, practical andbeneficial use of biosolids arising from thetreatment of municipal wastewater. Theseguidelines provide detailed information regarding:• permitted levels of contaminants in biosolids;• grading and monitoring of biosolids based on

quality and proposed end use;• restrictions on site suitability, such as buffer

distances to waterways;• determining safe application rates;• withholding periods for the resumption of

agricultural practices after application.

There are further DPIWE guidelines that provideadvice to operators and regulators regardingemission limit guidelines. Documents include the“Wastewater Management Guidelines forIntensive Animal Husbandry Activities” and the“Wastewater Management Guidelines for MeatPremises and Pet Food Works”.

Codes of practice provide guidance for aerial spraying,ground spraying and the supply and use of veterinarychemical products.


5.2 Minimise the impact of soil acidification

Practices that increase the impact of soilacidity

Some agricultural practices acidify soils. Suchpractices include:• excessive removal of alkaline product and

organic matter leading to a more acidic soilenvironment. As legumes (especially lucerne)can be highly alkaline, removal through cuttingand baling can cause soil acidification;

• frequent applications of nitrogen fertiliser (suchas ammonium fertiliser or urea). Thesefertilisers break down into nitrate and hydrogenions. The nitrate can then be leached, leadingto an accumulation of hydrogen ions in the soiland a decrease in pH;

• having extended fallow periods. Nitrates aresubsequently at risk of being leached duringfallow periods, leading to an accumulation ofhydrogen ions in the top-soil.

Guidelines• Get soil pH tested regularly (ie. 2 years for cropping, 5 years for pasture).• Apply finely ground liming material (without over-liming) to counter any

increase in acidity.• Avoid excessive removal of alkaline product (especially baled lucerne) from

the property.• Apply slow-release nitrate fertilisers rather than acidifying ammonium

fertilisers.• Minimise fallow periods and (where possible) favour deep-rooted perennial

species to maintain nitrogen cycling in the soil.

Acidification is a decline in soil pH. Soil pH is anindex (on a scale of 1 to 14) of soil acidity, which isa measurement of the concentration of hydrogenions in the soil.

Soils that become more acidic (pH lower than 7)have a reduced availability of some elements(such as phosphorus and molybdenum) whileother elements (such as aluminium andmanganese) may increase to toxic levels. Thisresults in stunted and yellowing pasture or crops,weed invasion and a decline in animal production.Soils with a water pH below 4.8 can be particularlytoxic and unproductive.

The rate of acidification depends on soil type andits starting pH and buffering capacity. Bufferingcapacity refers to capacity of the soil to maintainconstant pH levels despite the addition of acids.Sandy loams have a lower buffer capacitycompared to clay loams.

Countering inherently acidic soil

Most Tasmanian soils are naturally acid due to theeffects of leaching under high rainfall. Therefore,lime applications are sometimes required tocounter acidity and improve pasture and cropgrowth. For example, 110 kg ground limestone isgenerally recommended per 100 kg application ofammonium sulphate.

Mixing finely ground limestone or dolomite into thesoil is better than surface applications that maytake many years to dissolve. Over-liming soils mayreduce the uptake of nutrients by plants, and thisexcess lime may take years to be eliminated fromthe soil.

5.3 Prevent disease, pest and weed invasion

DPIWE can also provide contact details for thefollowing organisations:• The Tasmanian Weed Society, which offers

members with weed management information.• Local Community Weed Management

Strategies and Landcare groups, whichoperate in many parts of the State.

Guidelines• Monitor and control pest outbreaks.• Ensure that equipment going to and from the farm is clean on arrival and

departure.• Clean equipment used in paddocks infected by pests.• Use a suitable wash-down area for cleaning equipment.• Harvest paddocks least affected by pests first.• Restrict vehicles to tracks or headlands.• Rotate crops and pastures to disrupt pest lifecycles.• Work with neighbours and community groups to address pest problems on a

local scale.• Know the pest lifecycle to effectively target their most vulnerable stage.• Use certified seed or feed to minimise the risk of weed contamination.• Contact DPIWE for appropriate options for removing specific pests.

Weeds, soil-borne diseases, insects or other pestsof plants and animals have been generally definedin this section as a “pest”. More specificterminology is used where necessary.

The cheapest and most effective form of pestmanagement is prevention. Prevention reducesthe need for chemical control measures and helpsto secure markets that demand disease freeproduce.

Where pest invasion has already occurred, anintegrated management approach is required sothat pest populations remain below a thresholdlevel. This is the level at which the pest may still bepresent — without being an economic threat.

Further weed management information isavailable from DPIWE and a number of DPIWEpublications, including “Weed Plan”, “IntegratedPest Management” and a number of informationsheets.

The Tamar Valley Weed Strategy’s web site(www.weeds.tassie.net.au) assists with weedidentification and management.

Signs inform visitors about farm hygiene standards.

CHAPTER 6

MANAGING RIPARIAN LAND

This chapter discusses the practices to manageriparian land. The following practices arerecommended:• manage stock;• manage native vegetation;• minimise the impact of run-off into streams.

Riparian land occurs adjacent to streams, rivers, lakes and wetlands. It also occurs in gullies anddepressions, where water only flows during wet periods. Such areas can vary in width from a few metres towell over 100 metres. Riparian zones are vital to sustainable land management, even though such zonesoccupy only a small percentage of a catchment landscape.

Poor riparian management increases bank erosion and flooding, decreases water quality and degradesproductive land and riparian ecosystems. The width, vegetative composition and continuity of the ripariancorridors are critical for effective riparian management.

If resources are limited for riparian vegetation management, the most suitable initial strategy might be toprotect areas in good condition. This is a cost-effective strategy, as it is more expensive to restore adegraded area than to simply protect a healthy area.


6.1 Manage stock

Fencing

Fencing enables strategic management of riparianlands. The type and location of fencing dependson:• type of stock;• size and shape of a stream channel;• frequency and peaks of floods;• intensity of use of fenced riparian land;

Fence life can be prolonged by positioning fenceson higher ground or beyond the boundary of mostfloods. As the extent of potential floodingincreases, a wider fenced zone is recommended.Where active streambank erosion is evident, aminimum width of 10 metres is recommended.

Fencing along streams

Plain wire fences are recommended as theseoffer less resistance during floods. Reducedresistance to flowing water and debris means areduced risk of severe flood damage.

Electric fences (compared to standard fencesthat require more wires and posts) offer lessresistance during floods, cost less to install andare easier to install and move. Fitting electrifiedwires can be an inexpensive way of upgrading aconventional fence.

Guidelines• When possible, fence out stock from riparian land.• If stock exclusion is not possible on riparian land, minimise the impact of grazing.• Use fencing systems that effectively control stock.• Use fencing systems that have minimal risk of damage during floods.• Provide off-stream watering points.• If on-stream watering is required, provide limited access points with stoned

ramps.

Poorly managed stock on riparian land will result inovergrazing, trampling and soil compaction.Subsequently, the incidence of weed invasion andstreambank erosion increases. Water quality isdegraded as a result of increased erosion andincreased direct inputs of stock manure and urineinto streams.

Further information about managing stock on ornear riparian land is available from DPIWE,catchment committees and farm advisers.Extensive details of fencing and watering optionsfor stock are discussed in the DPIWE booklet“Managing Streamsides: Stock Control, Fencingand Watering Options”.

As riparian land is highly sensitive to grazing,stock exclusion in such areas is recommended.Any loss of grazing land due to fencing may beoffset by less flood damage and reducedmaintenance costs. River flats that are fenced offcan be utilised for hay production.

If exclusion of stock is not possible, strategicmanagement is recommended to minimise theimpact of grazing:• during the initial stage of the growing season to

allow for adequate annual growth;• during flowering and seed production to allow

for reproduction of vegetation cover;• following disturbance events (such as flooding)

that provide triggers for mass germination;• when there are signs of overgrazing, trampling

or soil compaction.

Regular inspections are necessary to monitor theneed to move stock. See Section 2.3 for furtherinformation about managing a flexible grazingsystem.

Fencing across streams

Several fencing options are available wherefences are required to cross the anticipated flow offloods.

Minimal cost fences consist of plain wires and asfew posts as possible, thereby offering littleresistance during floods. Financial loss is low if thefence is damaged or destroyed through flooding.Use of electrified wires further increase theeffectiveness of this fencing type.

Drop fences are either manually lowered before aflood or automatically lowered from their anchorpoints under the pressure of floodwater. Followingfloods, these fences can be quickly erected. Dropfences can also be lowered to allow stock orvehicle movement without the need for expensivegateways.

Suspended fences are built across narrowstreams to prevent stock wandering along thestream. The fences have hanging panels, planksor chains that lift upwards during floods and returnto their normal position when flows subside.Panels damaged by flood debris can be cheaplyrepaired or replaced.

Supplying water

Following fencing of riparian land, water accesspoints for stock may be required.

Off-stream access watering involves pumpingwater from a source to a trough or tank in apaddock. There is a range of cost-effectivepumping systems available, including:• stock operated pumps, whereby stock drinking

from a pump push a lever to provide power topump more water;

• water powered pumps, whereby the flow ofwater provides power to pump a small volumeof water to a trough;

• electric, wind and solar powered pumps.

Controlled access points (also known as gradedslopes) require sealing with compacted gravel orrock ramps to minimise erosion and pugging.Fences are required to extend into the water toprevent stock straying along the stream.Construction of stock access points in the bed orbanks of a watercourse require approval from yourlocal council.

The most appropriate locations for controlledaccess points is where streambank erosion isminimal. Streambank erosion tends to be minimalon the inside of a meandering river bend. The riskof erosion is highest in boggy areas and on theoutside of streambanks.

Note that floods may damage fences and rampsleading to the water. Therefore, controlled accesspoints may require repair or replacement whenfloods subside. The time and expenses requiredfor developing controlled access points may bebetter spent on fencing off riparian areas andproviding off-stream watering points for stock.

Dams or tanks with off-stream watering points orcontrolled access points. Contact a DPIWERegional Water Management Officer about thepotential requirement for a dam permit.

A drop fence.


6.2 Manage native vegetation

Higher up the bank, shrubs and trees withextensive and dense root systems arerecommended. These bind and dry out the soil toa greater depth, compared to plants with lessextensive root systems. The result is improved soilprotection and soil moisture conditions.

To ensure consistent vegetation cover, shrubs andtrees need to be planted in conjunction with grassand sedge species. Recommended speciesinclude Woolly Tea-tree, Black Tea-tree,Blackwood and Dogwood.

Further information about establishing andprotecting vegetation on riparian land is availablefrom DPIWE and in the “Kit 6 — Riparian Bush”,which is part of the Tasmanian Bushcare Toolkit.

Vegetation and woody debris withinchannels

Moderate occurrences of vegetation and largewoody debris in channels can provide resistanceto water. This reduces stream flow rates andthereby reduces the risk of erosion. However, thickstands of vegetation and woody debris within achannel can reduce stream flow rates to such anextent that blockages occur. This increases therisk of flooding and thereby streambank erosion.

Re-orientation (rather than removal) of suchobstacles is sufficient to minimise the risk offlooding. Debris dragged back against banks at a40 degree angle will minimise diversion of wateronto banks. Only in very choked channels doesthe removal of vegetation and debris lead toimproved flow capacities.

The removal of willow trees requires carefulmanagement. Further information is available inthe DPIWE Willow Management Guidelines.Contact DPIWE before commencing willowmanagement.

Guidelines• Use an effective fencing system to protect native riparian vegetation from stock.• Regenerate or establish appropriate vegetation that is indigenous to the local

area.• Manage in-stream obstructions that may increase the risk of erosion.• Seek advice from DPIWE for particularly unstable streambanks.

Dense vegetation reduces the risk of erosion bydecreasing flow velocity and binding the soil alongthe bank.

Native vegetation can readily regenerate inriparian areas where there is adequate remnantvegetation to provide a seed source. Where nativevegetation is absent or lacking in species diversity,planting may be necessary to successfullyestablish vegetation cover.

It is recommended to only establish riparianvegetation that is indigenous to the local area.Seeds collected from local areas will tend to bewell adapted to the conditions into which they arebeing established. An exception is the sowing ofannual grasses to assist in short-term soilstabilisation.

Establishment of riparian vegetation requireseffective:• weed management. See Section 5.3 for further

information;• exclusion or careful management of stock. See

Section 6.1 for further information;• prevention of browsing by possums, wallabies

and rabbits with the use of tree guards orwallaby fencing.

At the toe of the bank, perennial grasses andsedges are recommended. Their flexible leavesand stems are better able to move with flowingwater, compared to rigid plants that can breakduring peak flows. Their dense fibrous rootsystems are anchored into the soil during peakflows and thereby protect the soil from erosion.Recommended species include Sedge, MattRush, and Tussock Grass. A protective cover ofwoody debris or tea tree brush can help to stabiliseestablishing vegetation.

6.3 Minimise the impact of run-off into streams

Dams built within drainage lines can further reducethe flow of sediment into streams. If consideringconstruction of a dam, contact a DPIWE RegionalWater Management Officer about the potentialrequirement of a dam permit.

Maintaining buffer strips

To maintain a thick groundcover with a good heightto trap sediment, a well-managed grazing systemis required for grassed buffer strips. By rotating orexcluding livestock with the use of temporary orpermanent fencing, grazing pressure can be bettermatched to maintain pasture with adequate height.Regular inspections are necessary to monitor theneed to move stock.

See Section 6.1 for further information aboutmanaging stock on riparian land. Furtherinformation about buffer strips is available fromDPIWE.

Guidelines• Use riparian buffer strips in conjunction with improved soil management

practices on adjoining cultivated land.• Strategically locate riparian buffer strips according to anticipated volumes of

water and sediment.• Develop a well-managed grazing system within grassed buffer strips.

Sediment and some nutrients (particularlyphosphorus) can be carried to streams by surfaceflows from adjacent land. This sediment cancontaminate water supplies and smother habitatsfor fish and other animals. Vegetation can slow theoverland flow of water, causing sediment andnutrients to be deposited before reaching thestream.

Designing buffer strips

Water flows tend to become concentrated innatural drainage lines leading to a stream.Therefore, buffer strips only need to be locatedwhere water concentrates between cultivated landand streams. Buffer strips are ineffective filterswhen slopes exceed more than 10%, as run-offflows too rapidly for sediment to be trapped bygrasses.

As a general guide, an effective buffer stripconsists of a 10 metre wide grass buffer on theoutside of a 10 metre wide natural vegetation stripthat is adjacent to the stream. Wider buffer stripsmay be necessary where there is:• poor vegetation cover;• intense sources of contamination;• high volumes of run-off;• high levels of sediment movement.

Riparian buffer strips become ineffective if poorsoil management practices occur elsewhere onthe farm. Such practices can lead to high levels ofsoil erosion and contamination to an extent thatcannot be filtered by riparian buffer strips. SeeChapter 3 for further information about reducingsoil erosion and Section 5.1 for further informationabout managing chemical and fertiliserapplications. Filter effect.

AcidificationThe process of making soilmore acid.

Acid soilA soil with a pH of 6.6 or less.There are more hydrogen ionsthan hydroxyl ions in an acidsoil.

Alkaline soilA soil with a pH of greater thanabout 7.3, or a high sodiumcontent, or both.

AggregateGroups of soil particles that areclumped together to form thestructure of the soil.

AnnualsPlants that complete their lifecycle in 1 year or less.

BalingPressing hay or silage intosquare or round bales aftercutting and drying the pasturematerial.

BiosolidsThe solid proportion of organicwaste that can be treated andused as an agricultural fertiliser.

Black cracking claysBlack, well-structured, swellingclay overlying a mottled brownto greyish-brown clay.

BoreA drilled hole lined with tubingthat allows underground waterto flow in.

CatchmentA feature of the landscapewhich collects run-off.

ClayFine soil particles less than0.002mm in diameter. A soil thatcontains more clay than silt orsand.

CompactionPhysical degradation throughsoil compression.

ContaminantProduces undesirable effects onsoil and water quality if itsconcentration exceeds a certainthreshold.

ContourAn imaginary line on the soilsurface connecting points of thesame height above sea level.

Cover cropA crop that is grown to reducesoil erosion and protect anestablishing cash crop fromwind damage.

Cressy soilsDark grey-brown/brownloam/clay-loam topsoil overlyinga red-brown/grey-brown clay.CultivationWorking the soil withimplements in order to prepare itfor sowing.

Deep sandsDeep uniform sands, withtopsoils ranging from red-brownto grey-brown.

DispersionThe separation of soilaggregates into particles, as aresult of the presence of water.

Dispersive soilA soil that is capable ofdispersion.

Direct drillSowing with minimal cultivation.

Drainage lineA feature of a landscape downwhich water concentrates andflows.

Duplex soilsSoils having a distinct texturecontrast between topsoil andsub-soil.

EcosystemThe interacting biological andenvironmental parts of aparticular habitat.

FertiliserA substance that is added to thesoil to supply essential nutrientsfor plant growth.

FerrosolsKrasnozems. Red-brown/red,strongly structured, gradational,clay-loam/clay soils thatgenerally become darker, moreacidic and higher in organicmatter further inland.

FriableA soil that crumbles easily or iseasy to cultivate.

GrazierA landholder managing grazinganimals. Distinguished from afarmer who may cultivate landfor cropping.

Green manure cropA crop grown to improve soilstructure and soil organic matterlevels.

GroundwaterWater in the lower layers of thesoil.

HerbicideA material that will kill weeds.

IndigenousBelonging to, or forming part ofthe natural biological diversity ofa place.

Land Capability classesA system of classifying landaccording to its productivity foragricultural use.

LeachingThe downward movement ofnutrients or salts through thesoil profile.

GLOSSARY Source of many terms from Brouwer D (1999)

LegumeA plant, such as clover, peasand beans, that is able to fix(capture) nitrogen from the airby means of nodules on itsroots.

LoamA soil that contains moderateamounts of sand, silt and clay.

MottledSoil that contains more than onecolour in a horizon, oftenindicating poor drainage.

MulchingDevelopment of a layer oforganic material on the surfacesoil.

NoduleA small lump on the roots oflegumes in which rhizobiabacteria grows and fixesnitrogen from the air.

Organic matterCarbon-based materials ofeither plant or animal origin.

OrganismA living thing.

PastureGrasses, legumes and othergrowing plant material suitablefor grazing animals.

PerennialsPlants that live for more than 1year.

pHPotential Hydrogen. Themeasure of acidity. A pH lowerthan 7 is acid, higher is alkaline.

Pore spaceThe openings in a soil not filledwith solid particles.

PorosityThe ability of a soil to allowwater to move through it.

PuggingA process of soil degradation asa result of compaction byanimals during wet weather.

Quality assuranceStandards are set for a productor process that ensure that theend-product is of a predictablequality to improve itsmarketability.

RechargeRainfall or irrigation water thataccumulates in the watertable.

RhizobiaA bacterium that can infectlegumes in a beneficial way. Thebacterium takes nitrogen fromthe air and changes it into aform that the plant can use.

RiparianThe area close to a waterway,stream or river.

RippingAn operation that loosenscompacted soil.

Rotational grazingA process of rotating stockacross several paddocks.

Run-offThe flow of surface water over apaddock that can lead toerosion.

Run-onThe flow of surface water fromup-slope onto a paddock thatcan lead to erosion.

Saline soilA soil containing enough solublesalts to reduce plantproductivity, but not containingan excess of sodium.

Set stockingFixed number of animalsgrazing a paddock for anextended period.

SlashingCutting pasture or grass with amachine to remove excessmaterial or weeds from apaddock.

Soil profileDescription of each layer in thesoil.

Soil structureThe arrangement or grouping ofsoil particles.

Soil textureA measure of the proportions ofdifferent sized soil particles. Therelative amounts of sand, siltand clay in a soil.

Soil typeA general term used to describethe features of particular soils interms of fertility, colour, textureand parent material.

Stocking intensityThe number of stock in a givenarea.

StubbleThe dead plant materialremaining after a crop has beenharvested.

Sub-soilSoil in the lower horizons of thesoil profile.

SustainTo meet the needs of thepresent while leaving equal orbetter opportunities for thefuture.

TillageCultivation.

TopsoilThe part of the soil profile thatcontains the most fertile portionof the soil.

WatertableThe upper edge of free water.Water holding capacityThe ability of soil to hold water.

WaterloggedSoil that is saturated with waterand where most of the porespace has been replaced bywater.

WeedA plant growing where it is notwanted.

REFERENCESDrainage Information Package. Bastick C.H. and Cotching W.E. 1996, Department of Primary Industry andFisheries, Tasmania, Australia.

Glossary of Agricultural Terms. Brouwer D. 1999, NSW Agriculture —Tocal, Paterson NSW.

Integrated Pest Management — Using the Toolbox. Bishop, A. 2001, Tas-Regions 6 (5) & 6 (6).

Keeping your Soil on your Farm. Kindred Landcare Group 1994, Department of Primary Industry andFisheries, Tasmania, Australia.

Land Capability Handbook — Guidelines for the Classification of Agricultural Land in Tasmania. Grose C.J.(Ed) 1999, Second Edition, Department of Primary Industries, Water and Environment, Tasmania, Australia.

Managing Streamsides: Stock Control, Fencing and Watering Options. Wright D. and Jacobson T. (2000),Department of Primary Industry and Fisheries, Tasmania, Australia.

Managing Tasmania’s Cropping Soils — a practical guide for farmers. Chilvers W.J. 1996, Department ofPrimary Industry and Fisheries, Tasmania, Australia.

Weed Plan — A Tasmanian Weed Management Strategy. Department of Primary Industry, Water andEnvironment, Tasmania, Australia.

CONTACTSThis document consists of basic guidelines and information. Further information and contact detailspertinent to the document are available from the Department of Primary Industries, Water and Environment(DPIWE).

Marine Board Building,Hobart1 Franklin Wharf GPO Box 44 HOBART TAS 7001Telephone (03) 6233 8011Fax (03) 6234 1335

Lands Building, Hobart134 Macquarie StreetGPO Box 44 HOBART TAS 7001Telephone (03) 6233 8011Fax (03) 6233 6655

Within Tasmania, the general enquiry number for DPIWE is

1300 368 550

The DPIWE website is

www.dpiwe.tas.gov.au

Mt Pleasant Laboratories165 Westbury Rd, PROSPECT TAS 7249Telephone (03) 6336 5444Fax (03) 6336 5372

New Town Laboratories13 St Johns Avenue, NEW TOWN TAS 7008Telephone (03) 6233 6833Fax (03) 6228 5123

Prospect Offices167 Westbury Rd PROSPECT TAS 7249Telephone (03) 6336 5444Fax (03) 6336 5365

Stoney Rise CentreRundle Road DEVONPORT TAS 7310Telephone (03) 6421 7601Fax (03) 6424 5142