soil fertility testing

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Vineyard Soil Testing Vineyard 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.

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Page 1: Soil fertility testing

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).

Page 2: Soil fertility testing

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.

Page 3: Soil fertility testing

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

Page 4: Soil fertility testing

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

Page 5: Soil fertility testing

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

Page 6: Soil fertility testing

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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Page 7: Soil fertility testing

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

Page 8: Soil fertility testing

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

Page 9: Soil fertility testing

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

Page 10: Soil fertility testing

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

Page 11: Soil fertility testing

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

Page 12: Soil fertility testing

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?

Page 13: Soil fertility testing

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

Page 14: Soil fertility testing

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

Page 15: Soil fertility testing

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

Page 16: Soil fertility testing

Row Direction

Soil Sampling ApproachesSoil Sampling Approaches

Fixed GridFixed Grid

Random Zig ZagRandom Zig ZagEroded upper slope

Darker color down slope

TargetedTargeted

Page 17: Soil fertility testing

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

Page 18: Soil fertility testing

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

Page 19: Soil fertility testing

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

Page 20: Soil fertility testing

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.

Page 21: Soil fertility testing

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

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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

Page 23: Soil fertility testing

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:

Page 24: Soil fertility testing

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?

Page 25: Soil fertility testing

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)

Page 26: Soil fertility testing

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

Page 27: Soil fertility testing

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

Page 28: Soil fertility testing

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

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