Soil Sampling

Kwantlen Farm SchoolClass 3:Soil Sampling and Testing

Chris Thoreau

Class OutlineWhat is Soil Testing?What are We Testing For?Soil Sampling MethodologiesSoil TestingInterpreting Soil Test Results

What is Soil Testing?What are We Testing For?Soil Sampling MethodologiesSoil TestingInterpreting Soil Test Results

2Soil TestingWhat is Soil Testing?

Soil testing is the use of various laboratory methods to discover chemical and/or biological qualities of a soil sample as part of an overall soil management plan

Soil testing can also be used to discover the presence of contaminants such as heavy metals or pollutants

What is Soil Testing?

Soil testing is the use of various laboratory methods to discover chemical and/or biological qualities of a soil sample as part of an overall soil management plan

Soil testing can also be used to discover the presence of contaminants such as heavy metals or pollutants

3Soil TestingTesting for chemical properties is the most common type of soil testing and includes:pHOrganic Matter %NutrientsN, P, K, Ca, Mg, Fe, Cu, S, Mn, Zn, BC:N RatioElectrical Conductivity (EC)Cation Exchange CapacityBase SaturationParticle size distribution (texture)

Testing for chemical properties is the most common type of soil testing and includes:NutrientsN, P, K, Ca, Mg, Fe, Cu, S, Mn, Zn, BpHOrganic Matter %Electrical Conductivity (EC)Cation Exchange CapacityBase SaturationParticle size distribution (texture)

4Soil TestingSoil testing involves three basic stages:

SamplingTestingInterpreting

Which, ideally, lead to actions to improve our soil quality.

Soil testing involves three basic stages:

SamplingTestingInterpreting

Which, ideally, lead to actions to improve our soil quality.

5Soil SamplingSoil Sampling:

The process of collecting soil to be submitted for testing. The collected soil is called a sample

Soil must be collected carefully to ensure a representative sample is submitted for testing

Soil Sampling:The process of collecting soil to be submitted for testing. The collected soil is called a sample

Soil must be collected carefully to ensure a representative sample is submitted for testing

6Soil SamplingCollecting Samples 2 basic methods

1. Composite Samples:Several samples are taken from a field and then mixed together to get a representative sampleSamples must be taken randomly or in a set pattern to ensure a statistically representative sample is collected as we are collecting a small amount of soil to represent a large areaCollecting SamplesComposite Samples:Several samples are taken from a field and then mixed together to get a representative sampleSamples must be taken randomly or in a set pattern to ensure a statistically representative sample is collected as we are collecting a small amount of soil to represent a large area

7Soil SamplingCollecting Samples

Random SamplingRandom locations Easy way to get arepresentative sampleMust be truly random to be accurate!Zig-zag motion can besuitable

Collection Methods

Random SamplingRandom locations Easy way to get arepresentative sampleMust be truly random to be accurate!Zig-zag motion can besuitable

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Soil SamplingCollecting Samples

Topography SamplingVariation of randomsampling methodAddresses variation in field topography or field features

Collection Methods

Topography SamplingAddresses variation in field topography or field features

9Soil SamplingCollecting Samples

2. Variation Sampling:Samples are taken from a field in a fixed pattern and each sample is kept separateGood for identifying variations in a field Collecting SamplesVariation Samples:Samples are taken from a field in a fixed pattern and each sample is kept separateGood for identifying variations in a field

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Soil SamplingCollecting Samples

Grid SamplingGood for uniform field(s)Does not take into consideration topographyCan be used for variationsampling

Collection Methods

Grid SamplingGood for uniform field(s)Does not take into consideration topographyCan be used for variationsampling

11Sampling MethodologiesVariation in Fields e.g., OM and pH

Soil SamplingCollecting Samples Tools:Clean trowel and shovel; Oakfield probeClean bucketPlastic bag

Plus, if doing variation sampling:Individual BagsLabelsField Map

Collecting Samples Tools:Clean trowel or shovelClean bucketPlastic bag

Plus, if doing variation sampling:Individual BagsLabelsField Map

13Soil SamplingCollecting Samples in the field:After establishing sampling pointsRemove vegetation from soil surfaceUsing shovel, dig 20-30 cm deep hole in a small area (20 cm diameter hole)Mix soil in hole wellUsing trowel, scoop up a standard, level sample and place in bucket

Collecting Samples in the field:After establishing sampling pointsRemove vegetation from soil surfaceUsing digging tool, dig 20-30 cm deep hole in a small area (20 cm diameter hole)Mix soil in hole wellScoop up a standard, level sample and place in bucket

14Soil SamplingWhere dont we collect samples from?Anomalous/non-representative locationsAround treesField edgesNear manure or compost pilesAround standing water

Where dont we collect samples from?Anomalous/non-representative locationsAround treesField edgesNear manure or compost pilesAround standing water

15Soil SamplingOnce all samples have been taken

Collect about 1 litre of soil from your mixture of samplesPlace it in a bag and label itCollection dateName of field collected fromContact info for lab

Once all samples have been taken

Collect about 1 litre of soil from your mixture of samplesPlace it in a bag and label itCollection dateName of field collected fromContact info for lab

16Soil SamplingWhen is a good time to be sampling?Close to time when soil will be used or SpringOr, end of season to prepare for following yearTest for Nitrogen: mid- or late-season when soil is warmerWhen soil not too wet or dryIdeally test in the conditions in which plants will be growing

When is a good time to be sampling?Close to time when soil will be used or SpringOr, end of season to prepare for following yearTest for Nitrogen: mid- or late-season when soil is warmerWhen soil not too wet or dryIdeally test in the conditions in which plants will be growing

17Soil TestingOnce soil sample has been collected it needs to go to a lab

Where do we send our samples?Always to the same labRequest list of methods useMethods are all standardizedIf new lab:Confirm methods used and compare results to previous test

Once soil sample has been collected it needs to go to a lab

Where do we send our samples?Always to the same labRequest list of methods useMethods are all standardizedIf new lab:Confirm methods used and compare results to previous test

18Soil Testing

Soil Testing

Soil Testing

Soil Testing

Soil Testing

Interpreting Soil Test ResultsOnce you have test results you need to know what to do with them!Once you have test results you need to know what to do with them!

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Interpreting Soil Test ResultspH - Measure of soil acidity Or, the amount of H+ ions in soilMust measure pH in solution and residualScale is from 0-14 0 = acidic; 14 = alkaline/basicpH in coastal soils is usually acidicSoil Acidity is neutralized through additions of Lime (CaCO3)Amount of lime required depends on soil texture and OM contentpH - Measure of soil acidity Or, the amount of H+ ions in soilMust measure pH in solution and residualScale is from 0-14 0 = acidic; 14 = alkaline/basicpH in coastal soils is usually acidicSoil Acidity is neutralized through additions of Lime (CaCO3)Amount of lime required can depend on soil texture

26Interpreting Soil Test Results

Interpreting Soil Test ResultsChemistry of raising pH

pH Buffering

Adsorption Affinity:

Al3+>Ca2+=Mg2+>K+(H+) =NH4+>Na+

Chemistry of raising pH

pH Buffering

Adsorption Affinity:

Al3+>Ca2+=Mg2+>K+=NH4+>Na+

28Interpreting Soil Test ResultsBasic Liming RecommendationsContingent on measured pH, desired pH, clay content, OM %

Basic Liming RecommendationsContingent on measured pH, desired pH, clay content , OM %

29Interpreting Soil Test ResultsTable 3. Lime Application Rates to Raise Soil pH to Approximately 7.0Existing Soil pHLime Application Rate(pounds per 1,000 square feet)SandyLoamyClayey5.5 to 6.05.0 to 5.53.4 to 5.03.5 to 4.5203040502540557035508080 Lime application rates shown in this table are for dolomite, ground, and pelletized limestone and assume a soil organic matter level of approximately 2% or less. On soils with 4 to 5% organic matter, increase limestone application rates by 20%. Individual applications to turf should not exceed 50 pounds of limestone per 1,000 square feet. Avoid the use of hydrated or burned lime because it is hazardous to both humans and turf (can seriously burn skin and leaves). If hydrated lime is used, crease application rates in the above table by 50% and apply no more than 10 pounds of hydrated or burned line per 1000 square feet of turf.

30Interpreting Soil Test ResultsOrganic Matter %% is by soil weightIdeal levels = 12-20% or moreIf tests show amounts below this level add more organic matter!

Organic Matter %Ideal levels = 12-20% or moreIf tests show amounts below this level add more organic matter!

31Interpreting Soil Test ResultsC:N RatioShould be 15:1 to 24:1If higher than 24:1, be careful to not add woody or high carbon materials to soil

C:N RatioShould be 15:1 to 24:1If higher than 24:1, be careful to not add woody or high carbon materials to soil

32Interpreting Soil Test ResultsElectrical Conductivity (EC)Measure of salt content in soilTests should return levels below 4 mmhos/cmRare to have high salts in soil around hereUse gypsum to remove sodium in soilFlushing water with soil important

Electrical Conductivity (EC)Measure of salt content in soilTests should return levels below 4 mmhos/cmRare to have high salts in soil around hereUse gypsum to remove sodium in soilFlushing water with soil important

33Interpreting Soil Test ResultsCation Exchange CapacityMeasure of soils ability to hold and release positively charged particlesCa2+, Mg2+, K+, Na+, H+, Al+Higher CEC value is better>15 meq/100g soil or 20 cmol/kg soilOM and clay both have high CECCEC Animation

Cation Exchange CapacityMeasure of soils ability to hold and release positively charged particlesCa2+, Mg2+, K+, Na+, H+, Al+Higher CEC value is better>15 meq/100g soil or 20 cmol/kg soilOM and clay both have high CECCEC Animation

34Interpreting Soil Test ResultsBase SaturationFraction of cation exchange sites occupied by base cations (Mg2+, Ca2+, Na+, K+)Usually expressed as a percentage

Base Saturation increases with soil pH

Base SaturationFraction of cation exchange sites occupied by base cations (Mg2+, Ca2+, Na+, K+)Usually expressed as a percentage

Base Saturation increases with soil pH

35Interpreting Soil Test ResultsBase SaturationIdeal proportions of Base cations60-75% Calcium10-15% Magnesium 3 5 % Potassium