Country Noosa24th October 2015Ridgewood

Soil nutrition workshop

Graeme Elphinstone, Grazing Lands consultant Brad Wedlock, MRCCC

• Soil consists of soil mineral particles, nutrients, organic matter, air, water, living organisms and pore spaces

• Soil minerals combine with organic matter to form peds separated by pore spaces

Soil components

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• Peds are made up of the primary mineral particles (clay, silt and sand) and organic matter

• The peds are held together by the electrical charges on the surfaces of the minerals and organic matter

• Most nutrient cations and anions attached to the soil are held by charges on the clay and organic matter

Peds – the building blocks of soil

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• As plant roots grow through the soil, they contact nutrient cations and anions held on the soil particles or dissolved in soil water.

• Most nutrient uptake happens through root hairs near the tip of young actively-growing roots

Nutrient uptake

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• Under grazing systems, nutrients are continually removed from the land in plant and animal products

• Nutrients fall into two groups; the major elements that are needed in large amounts, and the trace elements that are needed in very small amounts

• The major or macronutrients are nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca) and magnesium (Mg)

• Pastures require particularly large amounts of N and P for animal productivity

• Most Australian soils are naturally deficient in P

Nutrient types

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Liebigs law of limiting nutrients barrel(ie the weakest link in the chain)

Plants will not grow properly if any one nutrient is lacking

• Fertiliser types can be grouped as natural or synthetic ie manufactured; and also as organic or inorganic depending on whether they contain carbon

• Natural fertiliser products include animal manures, seaweed, crop residues, composts, rock minerals etc, as long as no manufactured products have been added. Blood & bone sits somewhere in-between.

• Rock mineral products used in agriculture include Ag lime, dolomite, gypsum, rock phosphate, various basalt or granite rock dust products etc

Fertiliser types

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Average nutrient analysis of animal manure fertiliser products

nitrogen phosphorus potash Dry matter

Deep litter poultry manure 2.5% 1% 1.5% 75% (50-90)

Pig effluent sludge 1% 3% 1% 50%

Cattle feedlot manure 2% 1% 1% 75%

An application rate of 2 cubic metres = ~1 tonne/ hectare, will provide the following amounts of nutrients per hectare:

nitrogen phosphorus potash Dry matter

Deep litter poultry manure 19 kg/ ha 7.5 kg/ ha 11 kg/ ha 75% (50-90)

Pig effluent sludge 5 kg/ ha 15 kg/ ha 5 kg/ ha 50%

Cattle feedlot manure 15 kg/ ha 7.5 kg/ ha 7.5 kg/ ha 75%

Country Noosa workshop 24 October 2015

* nutrient amounts based on 100% dry matter

9Country Noosa workshop 24 October 2015

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Cation exchange capacity – CEC* The CEC is a measure of potential fertility. It measures the soil’s ability to attract, hold and exchange cations in the soil for uptake by the pasture plants. * Such soil nutrients include calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), and aluminium (Al)* This applies equally to existing soil nutrients and those added nutrients applied as either organic or synthetic type fertilisers

A clay particle with its surface store of negative charges and the

balancing swarm of adsorbed positive ions (cations)

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Influence of soil pH on availability of plant nutrients(pH is a measure of acidity or alkalinity)

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Quote

“I look after my pastures…

My pastures look after my cattle…

My cattle look after me.”

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Building resilience into your pasture systems

•Pastures dominated with 3P pasture grasses

•Legumes are the key to pasture sustainability

•Wet season spelling

•Ensuring reliable stock water via tanks and troughs in all paddocks in all seasons

•Re-positioning cattle camps away from drainage lines

•Retaining soil nutrients on the pasture

•Target the weakest link in the soil nutrition chain first

•Single element fertilisers are the most cost effective

•Seasonal calving

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Seasonal Pasture Quality & Animal Weight Gain

Source: Best Start, Best Finish presentation – Greg Bath, Future Beef

15Source: Future Beef

Soil phosphorus importance

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Elements Test Results Other Units ConversionFactors

Interpretation & Comments Recommendations

pH (1:5 in water) the CaCl2 test results can be misleading

nil (pH 6.0 is optimal for tropical pastures)

Electrical Conductivity (EC)

dS/m mS/cm these units are the same

Organic Carbon (OC) %C Animal manures will help to build soil organic matter

Nitrate Nitrogen (N)KCl

mg/kg N ppm N these units are the same

Soil N readings under growing pasture are not indicative of N requirements

Phosphorus (bicarb-Colwell method)

mg/kg P ppm P these units are the same

20 mg/kg is the desired level

Sulfate Sulfur (S)MCP

mg/kg S ppm S these units are the same

Potassium (K)Amm acetate

meq/100g K ppm or mg/kg multiply by 391 0.25 meq/100g is the desired level

Calcium (Ca) Am acet meq/100g ppm multiply by 200

Magnesium (Mg) Am acet meq/100g ppm multiply by 121

Sodium (Na) Am acet meq/100g ppm multiply by 230

Aluminium (Al) meq/100g % saturation Divide Al by CEC <2% saturation is optimal

Total Cation Exch Capacity (CEC)

meq/100g 10 to 20 meq/100g is optimal

Chloride (Cl) mg/kg ppm <100mg/kg is optimal Zinc (Zn) DPTA mg/kg ppm >0.5 mg/kg is optimal Copper (Cu) DPTA mg/kg ppm >0.3 mg/kg is optimal Manganese (Mn) DPTA mg/kg ppm Iron (Fe) DPTA mg/kg ppm (iron deficiency is rare on low pH soils) Boron Hot H2O mg/kg ppm

Soil Analysis Interpretation for High Rainfall Sown Tropical Pastures

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Lab results (ppm) 0 - 10 10 - 15 15 - 20 20 - 25 30 (optimum)

Phosphorus (kg/ ha) 30 20 15 10 0

Lab results (meq/ 100g) 0.1 0.2 0.25 0.3(optimum)

Potassium (kg/ ha) 50 40 test strip 25 0

Lab results (ppm) 0 - 5 5 - 10 10 (optimum)

Sulfur (kg/ ha) 25 10 0

Interpreting and converting laboratory soil analysis results to elemental phosphorus, potassium and sulfur recommendations for sub-tropical pastures

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Country Noosa24th October 2015Ridgewood

Introduction to Setaria management

Graeme Elphinstone, Grazing Lands consultant Brad Wedlock, MRCCC

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Role of setaria (S. sphacelata) in sown pastures in coastal SEQ

•One of the most important sown pasture grasses in coastal Qld

•Planted extensively under the Dairy Pasture Subsidy Scheme (1966-1975) and the Wallum Development Scheme (1960-1975)

•Originated in the southern half of the African continent where it is both widespread and dominant over large areas

Plant characteristics•A tufted perennial 3P grass with a cylindrical spike seedhead

•The setarias are adapted to wet conditions (>1000mm AAR); well adapted to both sandy and clay soils, and tolerant of waterlogging

•Setaria has a long growing season, from early spring to early winter

•The first released cultivars eg Kazungula, are heavy seed producers

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Varieties of setaria•Four main commercial cultivars:

• Kazungula• Nandi• Narok• Solander

•Narok and Solander have the most frost tolerance (winter greenness)

•Setaria splendida – Giant setaria (very little planted in SEQ)

Oxalate•All strains of setaria contain oxalate; Kazungula has the highest level, Nandi the lowest, Narok and Solander intermediate, and native grasses virtually none

•Oxalate poisoning in cattle is fairly rare. The oxalate concentration in the plant is highest in the leaf blade and lush leafy growth about 2 to 4 weeks old.

•Note – cautiously introduce hungry cattle to a paddock of lush setaria

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Legumes in Setaria

•Legume compatibility with setaria is generally poor because the dense sward provides extreme competition for light, moisture and nutrients

•Companion legumes are more likely to persist in the more open mixed setaria swards with other less competitive grasses eg Rhodes

•The most compatible legumes are Wynn cassia and Shaw creeping vigna (on warmer hillslopes), and white clover (on cooler southerly hillslopes and creek flats)

•Grazing management and soil fertility are critical for legume persistence

•As with companion legumes, setaria is not very compatible with other pasture grasses, and tends to dominant the sward over time

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Soil nutrition for setaria

•A gross feeder of potassium and nitrogen

•At low soil fertility levels, setaria will persist but not produce

•Needs adequate levels of nitrogen, phosphorus & potassium for productive growth and animal weight gain

•Capable of responding to very high levels of nitrogen and is an exceptionally heavy feeder of potassium

•Setaria can induce potassium deficiency in soils which are not normally regarded as being potassium deficient

•Preferred soil pH range is 5.5 to 6.5

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Grazing management strategies for setaria pastures•Most setaria pastures are dominated by setaria with very few other grasses, companion legumes or forbs present ie a virtual monoculture•Pasture yield potential is high, in the order of 10,000 kg DM per ha, with a marked growth peak in mid-summer, when most seed production occurs

•The coarse stemmy seed stalks are poorly grazed by cattle, have a low nutritive value, and animal performance suffers accordingly

Slashing•On smaller sized grazing properties, slashing seed stalks immediately after each rotational grazing will reduce seed production and stimulate the regrowth of new basal tillers; likewise regrowth from the nodes on the lower seed stalks

•Avoid the slasher wasting palatable leaf growth by using a height-adjusting jockey wheel

•Slashing is not an option on commercial-sized properties

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Grazing management strategies – grazing rotations•Grazing rotation intervals should not be fixed, and must be adjusted in terms of both the seasonal growth rhythm of the setaria and local rainfall events

•During the peak summer growth phase, rotation intervals should not exceed 3 weeks, and wet season spelling would not normally be advised for healthy setaria-dominated pastures because of rank stalky tillers and seed heads. This then creates the opportunity to wet-season spell other non-setaria dominant paddocks on the property

•By comparison, winter rotation intervals could be as long as 2 to 3 months

• The mineral particles are clay, silt and sand

• Soils can be named according to their proportions of clay, silt and sand using the texture triangle

• Clay and organic particles hold most soil nutrients

Soil properties texture triangle

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Managing sodic soils in pastures

Managing sodic soils – CRC Soil and Land Management introduction to soil sodicity tech noteCaption - Reclaiming a sodic soil (twin diagrams)

•About 30% of agricultural land in Australia is sodic. This is about five times the area of saline land.

•Sodicity is caused by the presence of sodium attached to clay in the soil.

•Applied calcium in the form of lime or gypsum will displace the sodium from the soil surface, which is then leached deeper into the soil.

•Pasture growth and plant residues should be retained on the soil surface to build up soil organic matter, and not removed by burning etc.

•The organic matter will not only help to hold the applied calcium in place, but will also improve the soil structure.

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Strategies to produce additional quality pasture dry matter during an El Nino event

•The 3 basic tenets of growing grass is energy from the sun, rain from the clouds and/ or stored soil moisture, and various sources of nitrogen

•The optimum grass species for nitrogen top-dressing over the summer period are Callide Rhodes grass and pangola grass.

•The optimal grass specie for nitrogen top-dressing in late summer / autumn is kikuyu (winter-green setaria varieties would be second best)

Alternate sources of nitrogen fertiliser•Animal manures (deep litter poultry, pig sludge, cattle feedlot manure)•Urea (1 tonne bags)•Fertiliser sweepings (1 tonne bags – ex Incitec factory)

Indicative nitrogen application rate = 50kg/ ha of elemental N

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