soil fertility testing
TRANSCRIPT
Vineyard Soil TestingVineyard Soil Testing• Soil sampling and testing in viticulture is most important
prior to vine establishment.
• However, soil evaluation in mature vineyards is conducted when nutritional disorders are observed in vines or fruit yield or quality changes significantly.
• The most common type of soil testing is related to soil chemistry (e.g. pH or boron).
• Soil can also be evaluated for physical properties (e.g. water retention and release) and biological
properties (e.g. nematodes, microbial populations).
EXAMPLE: Lab Tests for Root MunchersEXAMPLE: Lab Tests for Root MunchersNot all soil organisms are beneficial and not
all are visible. There are times when a nematode or fungal pathogen test may reveal a hidden source of productivity decline.
Many of the soils in Western Oregon share some common ‘nutritional concerns’ based on either low content or availability, natural imbalances or other problems related to prior uses, crops, or management history.
Cations (+) Anions (-)Potassium, Manganese, Zinc Sulfate-S, Phosphorus, Boron
Other Issues Soil acidity (< 5.5), high magnesium
Vine Nutrients – Vine Nutrients – The Typical Soil TestThe Typical Soil Test
Soil pH and Nutrient AvailabilitySoil pH and Nutrient Availability
Soil pH is an important chemical property influencing vine nutrient bioavailability
Grapes are generally adaptable to soil pH ranges of 6 to 7.5 where most nutrients are most soluble.
Toxicity problems can occur at low pH where Al, Mn, and Fe have increased solubility in soil solution
Factors Affecting Soil AvailabilityFactors Affecting Soil Availability Nitrogen (N) – Organic, ammonium (NH4
+), nitrate (NO3-)
Low vine N is more common than excessive vine N Soil Organic Matter Organic N may be up to 99 percent of total soil N
Microbial activity (soil temperature, moisture, oxygen)
Soil pH
Clay content (protein adsorption, humus stabilization)
Fertilizers – (differences between organic and inorganic)
Volatilization, Denitrification, Leaching
Tillage, cover crop practices, mowing
Factors Affecting Soil AvailabilityFactors Affecting Soil Availability Phosphorus (P) – soluble (as H2PO4
-, etc.) organic forms,
bound with Al, Fe, and Ca compounds
Soil pH – effect on free (reactive) Al3+, Fe3+, and Ca2+
Low pH increases free Al and Ca, decreases P High pH increases free Ca, decreases P
Clay content and type (adsorption potential) P binds to Exch. Al or Fe, greatest in acid clay soil
Active (microbial) and Passive (humus) SOM
Microbial activity (soil temperature, moisture, oxygen)
Fertilization and N availability
Growth rate and size of root system
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Clay
H2PO4-
Factors Affecting Soil AvailabilityFactors Affecting Soil Availability Potassium (K) - soluble, exchangeable, fixed, insoluble
CEC, clay type (illite, vermiculite clay minerals)
Diffusion Affected by moisture, soil structure, clay, temperature
Form of N in soil High soil nitrate increase K absorption, high ammonium decreases K
Solution and exchangeable Mg and Ca
Factors Affecting Soil AvailabilityFactors Affecting Soil AvailabilitySulfur (S) - soluble (as SO4
2-), organic, adsorbed to Al and Fe compounds, inorganic compounds
SOM (all forms) Organic S may be up to 90 percent of total soil S
Soil pH – acidic lower, alkaline higher
Amount of free Fe and Al (acidity)
Competition at root surface with soluble soil P
Soil texture Soil moisture and leaching
Zinc (Zn) - soluble, exchangeable, adsorbed to Fe and Al compounds, low solubility SOM complexes and mobile chelates, insoluble Zn-minerals
Total soil Zn from parent material
Soil pH
SOM
Weather Cloudy (low light) and cool conditions decreases uptake and transport
Soil solution P High P reduces Zn uptake (competition), binding with P possible
High P-induced reduction of mychorrizal infection reduce Zn absorption
Factors Affecting Soil AvailabilityFactors Affecting Soil Availability
Boron (B) - soluble (neutral and anion), OM complexes, adsorption by Fe and Al compounds
B tends not to be in insoluble inorganic compounds
Total amount of B from parent material
Soil texture and moisture
Soil pH
Leaching
Factors Affecting Soil AvailabilityFactors Affecting Soil Availability
What Type of Soil Test?What Type of Soil Test?
Few commercial laboratories offer every type of soil test Engineering properties, hazardous chemicals, nutrient analysis, diseases, nematodes, microbial diversity
Become informed about various agricultural ‘package’ Become informed about various agricultural ‘package’
options and costs before you submit your soiloptions and costs before you submit your soil
Soil testing encompasses a bewildering number of methods and costs from kits to laboratories
Why use a lab when you can buy and use a kit? Higher ‘resolution’ and certified objective results
Soil Sampling and TestingSoil Sampling and TestingThe simple and critical key to getting any value from soil testing is collecting a representative sample
What is your question?What is your question?How large is your block? How many sub-samples?
How deep is your soil?
How uniform is your soil?
Soil Sampling and TestingSoil Sampling and TestingThe simple and critical key to getting any value from soil testing is collecting a representative sample
Sample the entire Sample the entire effective root zone effective root zone depth based on depth based on soil soil and vine age/sizeand vine age/size
Soil Sampling and TestingSoil Sampling and TestingThe simple and critical key to getting any value from soil testing is collecting a representative sample
Sample the entire Sample the entire effective root zone effective root zone based on based on soil profile soil profile depthdepth
Soil Sampling ApproachesSoil Sampling Approaches
Random or ‘Zig Zag’ For uniform sample areas
Targeted or Sub-Sampled When properties are known or suspected of having significant variation
Fixed Grid Applied in planted blocks/fields. Establish fixed locations for long-term monitoring of changes
The first step is to assess the area of interest How uniform is the topography? Does the current vegetation show uniform growth? Topsoil color or texture changes Take some pre-samples to your depth of interest
Row Direction
Soil Sampling ApproachesSoil Sampling Approaches
Fixed GridFixed Grid
Random Zig ZagRandom Zig ZagEroded upper slope
Darker color down slope
TargetedTargeted
The ‘Typical’ Soil Test – The ‘Typical’ Soil Test – What happens in there?What happens in there?
Generally lab procedures for handling (extraction) and quantitative analysis are similar for labs within a region
There may be important differences between regions that will make lab more appropriate than another.
• Sample preparation Drying, sieving, and grinding
• pH and ECe methods
• Chemical extractants and sample digestion methods
The ‘Typical’ Soil Test – The ‘Typical’ Soil Test – What happens in there?What happens in there?
METHODSSoil samples are first dried, ground and sieved for different analyses.
• Extraction and DigestionFor availability analyses, samples are treated with different chemical solutions (water, salt, dilute acid or alkaline solutions) that displace the target nutrient [s] from soil.
For total nutrients (e.g. SOM, organic N) a finely ground sample may be decomposed in hot acid (wet combustion) or high
temperature oven (dry combustion)
• Sample Analysis Drying, sieving, and grinding
Testing for Available Soil NTesting for Available Soil NThe dynamic nature of inorganic N in soil is difficult to ‘chase’ and most often the results from a conventional lab test are not very useful. The exception may be for deep profile sampling for specific residual N tests for crops other than grapes.
Typical lab reporting of nitrate and ammonium-N on dried and sieved samples have little value
If necessary, soil nitrate and ammonium tests are best performed on fresh moist soil, not dried or overly sieved
The Soil ReportThe Soil Report – Concepts and Units – Concepts and Units
There are no standard formats for soil test reports. While generally lab procedures for handling (extraction) and quantitative analysis are similar for labs in regions, there may be differences between regions.
The biggest challenge is in deciphering the interpretation. Labs provide results in many different formats, and may (or not) include diagnostic interpretations like low, medium, or high.
Soil test reports will, at a minimum, report nutrient levels on a concentration basis.
The Soil Report – Concepts and UnitsThe Soil Report – Concepts and UnitsTotal vs. Available As example, a test for organic N says very little about the bioavailability of soil N.
In the early portions of the 20th century, soil tests estimated the total nutrient. However, these results did not correlate well to crop productivity.
Therefore, modern soil testing attempts to determine the availability of a given nutrient by extracting more easily soluble forms.
Many field experiments have been conducted to evaluate how different crops respond and accumulate nutrients in different soils and after fertilization. By correlating extraction methods and results to crop responses, the indicies of available nutrients have been developed
The Soil Report – Concepts and UnitsThe Soil Report – Concepts and Units
Exchangeable versus water soluble While most labs will report the major exchangeble cations (e.g. Ca, K), few conduct either water- or dilute acid soluble extractions that better mimic the soil solution.
Units ppm = mg/kg and mg/L % = 10,000 ppm Meq = milliequivalents (exchangeable cations
Other units ECe = Electrical Conductivity or salinity = mmhos/cm (mmhos x 640) = Soluble salts in ppm
The Soil Report – Concepts and UnitsThe Soil Report – Concepts and Units
Conversion of concentration (ppm) to lbs per acre requires an ‘average’ assumption about bulk density and depth of soil.
e.g. 30 ppm P (12 inch sample) x ~4 = 120 lbs/acre
30 ppm P (6 inch sample) x ~2 = 60 lbs/acre
Conversion of nutrient concentrations in soil samples to estimates of the quantity present in a field, orchard, or vineyard, is typically done to provide available nutrients on a per acre (or hectare) basis.
Recall the concept of an acre furrow slice (one acre, 6 inches deep). While labs do not measure (or know) the actual bulk density of a soil, they use a standard conversion:
The Soil Report – InterpretationThe Soil Report – Interpretation
Questions to ask yourself Did the lab estimate lbs per acre based on your actual soil sample depth?
Have you sampled the potential or existing root zone?
Are the roots in your vineyard horizontally distributed throughout the entire soil?
In drip-irrigated vineyards… are there differences between the drip zone volume and remaining soil?
The Soil Report – InterpretationThe Soil Report – Interpretation
___________________________________________________ Exchangeable Cations Ratios ------------- percent of total ---------------- Ca Mg K Na Ca:Mg K:Mg___________________________________________________ 60-80 15-30 5-10 < 6 2-10 0.1-0.4___________________________________________________
Criteria for Sustainable Vine Health CISRO, Australia 2004
As grapevines are tolerant and reasonably adaptable to differing soil environments there is a broad acceptable range for typical soil nutrient properties. The below ranges for exchangeable cations (as a percentage of CEC) have been published in Australia.
(Note these numbers are not actual quantities, but reflect the distribution as a percentage of total soil CEC)
The Soil Report – InterpretationThe Soil Report – Interpretation___________________________________________________ Nutrient Deficient Marginal Adequate High Toxic ---------------------- mg/kg -----------------------___________________________________________________ Nitrate < 1 1-2 2-10 > 10 --
P < 25 25 -35 35-70 > 70 --
K < 50 50-100 100-250 > 250
S < 10 -- -- --
Zn < 0.5 0.5-1 1-2 2-20 > 20
B < 0.1 0.1-0.5 0.5-1 1-3 > 3
Al > 100___________________________________________________
CISRO 2004
Soil pH and Nutrient AvailabilitySoil pH and Nutrient AvailabilityLime is used to effectively increase soil pH
Sulfur or ammonium sulfate is used to decrease soil pH
pH Buffering CapacitypH Buffering Capacity
Clay and organic soils resist changes in pH
Sandy soil pH is more easily changed
Soil pH and Nutrient AvailabilitySoil pH and Nutrient AvailabilityDetermining Lime Requirement
pH Buffering Capacity is determined by measuring soil pH in distilled water and after ‘equilibration’ with a salt solution that is strongly ‘buffered’ at pH 7.5 (SMP buffer)
SMP Tons lime needed to pH pH 5.3 5.6 6.0 6.4
6.6 - - - 1.1 6.4 - - 1.1 2.2 6.2 - 1.0 2.0 3.2 6.0 1.0 1.7 2.9 4.2 5.5 2.6 3.6 5.1 6.8 5.0 4.2 5.4 7.3 9.4