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Soil

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Why Guess When You Can Test?

Accurate soil test results build the foundation of a strong soil fertility program. A fertility management program based on information from soil test results can benefit the grower in many ways.              

Role and Value of Soil Testing

  • Evaluate fertility status and monitor soil conditions to track trends over time
  • Assist in predicting the correct type and amount of fertilizer needed
  • Troubleshoot problem areas
  • Improve yields and profitability from providing proper nutrient
  • Increase the uniformity of nutrient availability across a field
  • Optimize plant response to management inputs, competition from weeds or weather conditions
  • Achieve uniform maturing dates for all plants within a field, which simplifies harvesting and drying of the crops

Soil Sampling Guide

Scroll down the page for sampling instructions or Click Here for a PDF copy.

Soil Grid Information Sheet Click Here
Sample Report - Soil Grid Click Here
Sample Report - Grid Plus Recs Click Here
Sample Report - Soil Summary Diagnostic Strawberries Click Here
Sample Report - Triple Option Routine Click Here
Sample Report - Triple Option Diagnostic Click Here

SOIL TESTING OPTIONS
Basic Test Package:

Soil pH
Buffer pH
Soluble Salt
Excess Carbonate,
Organic Matter
Sodium                                  

Phosphorus
Potassium
Magnesium
Calcium
CEC, Percent Base Saturation
Results & Guidelines
Routine Package:

Soil pH
Buffer pH
Soluble Salt
Excess Carbonate
Organic Matter
Sodium

Phosphorus
Potassium
Magnesium
Calcium
Nitrate
Sulfur
Zinc
CEC, Percent Base Saturation
Results & Guidelines
Diagnostic Test Package:
Soil pH
Buffer pH
Soluble Salt
Excess Carbonate
Organic Matter
Sodium
Phosphorus
Potassium
Manganese
Calcium
Nitrate
Sulfur
Zinc
Magnesium
Copper
Iron
Boron
CEC, Percent Base Saturation
Result & Guidelines
Additional Analysis
(can be added to a package or ordered separately)
Traces (Zn, Mn, Cu, Fe)
Nitrate
Sulfur
Zinc
Boron
PSA (Soil Texture)
Salinity
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Bray II
Molybdenum
Chloride
Arsenic, Extractable
Profile Nitrate
Profile Chloride
Soluble Nutrients
 

SOIL SAMPLING PROCEDURES

PROBEPLASTIC BUCKETSOIL SAMPLE BAG
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SAMPLING PROCEDURES

In order for a soil test to be an effective monitoring tool, sampling procedures need to be consistent from one year to the next. This is where field histories come in. Factors such as sample depth, area represented, time of year, number of sub-cores and sampling equipment should be the same each time the field is sampled.                    

SAMPLING DEPTH

Most surface samples are taken from a depth of 0 to 6 to 0 to 8 inches. This is where management of fertilizers and soil amendments occurs, meaning this is the volume of soil that will be affected by a grower's management. The exception to this is the mobile nutrient which has the ability to move with the soil water: nitrate, sulfate and chloride. In addition to the surface it is recommended that these mobile nutrients also include a profile depth of 6 to 24 or 6 to 36 inches. These profiles need to be collected into a separate bag with the depth labeled.                    

Of all the factors affecting consistency of a soil test system, sample depth has the greatest influence. Below is a table demonstrating the affects of a tillage system and sample depth on phosphorus soil test values:                    

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Soil Sampling Depth and its affect on Soil Test Phosphorus (Bray I-P)

 Tillage System
Sample Depth (Inches)Plow P ppmChisel P ppmNo-Till P ppm
0-155104172
1-25010474
2-3449442
3-6403822

Stratification in Reduced Tillage

For sampling in no-tillage systems maintaining sample depth is even more important. Immobile nutrient (such as phosphorus) build on the soil surface with broadcast fertilizer applications. At some point in time it becomes important to determine the degree of stratification. It is suggested that a sample unit/area be used as a test, instead of a 0 to 6 inch sample depth, perform a split sampling of 0 to 3 inches and also from 3 to 6 inches. This split sampling allows the determination of stratification. If the second depth (3 to 6) is 50 % of the surface depth (0 to 3), significant stratification has occurred. Further, broadcast applications without tillage will continue the process. It would be advisable to recommend a deep tillage and begin the no-till process over.                            

Representative Area Sampling                            

Conventional Sampling System

Several options are available for determining how to divide field/fields into individual soil samples. If the field is less than 20 acres the whole field can be made as one sample. If greater than 20 acres then multiple samples are required. Topography, soil type or even divisions can do this division. It is important to remember that unusual areas (farmsteads, fence rows, ponded areas, blowouts, etc.) need to be avoided or sampled separately. Old farmsteads are still apparent decades after they are abandoned.                            

When sampling, 15 to 20 sub-cores are needed for providing a representative sample, more would be even better. In addition the laboratory needs at least 8 ounces or 1 pound of material in order to perform all analysis.                            

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GRID Soil Sampling

Grid soil sampling involves dividing the whole field into small equal sized grids. Most grid sizes comprise 2.5 up to 5 acres. The soil cores from each grid are collected either from the center point or from random points through out the grid cell. A minimum of 10 cores is needed in order to provide the laboratory with enough soil to perform analyses.                            

Time of Year to Sample

The time of year (Early fall - vs. - spring) can have an affect on analytical results. For monitoring, it is recommended that samples be collected during the same season: late fall, winter, spring and summer. Do not rotate your sampling schedule.                            

Research conducted at the University of Wisconsin

MonthpH (ppm)Organic Matter %P (ppm)K (ppm)
September6.72.218140
October6.93.318110
November7.13.718110
December7.24.225170
January6.92.728130
February7.22.819150
March7.53.419120
April7.23.219105
May6.82.819113
June72.81992
July72.31080
The variation in the test data is due to the natural variability of: wetting and drying, freezing and thawing, plant nutrient uptake and nutrients released from residue decay. Since these changes occur at differing rates each year it is difficult to predict what changes might occur. For this reason, pick the season most convenient for your operation and stick with it.

Sample Handling

Proper handling of the sample is important to maintain the integrity of the soil. Soil is a biologically active material, this activity continues even after the sample has been collected. It is necessary to collect and ship no later than the next day. If storage is required, three options are available; dry the soil with low heat (not greater than 120 F), store in a freezer or at least refrigerate. These processes will slow down or stop the biological activity, preserving sample integrity.                                             

Sample Submittal Forms

To streamline the laboratory's handling (to assure fast turnaround) of the received samples include laboratory submittal forms. Laboratory supply order form and submittal forms (sample sheets) are available at AgSource Laboratories.                                             

Essential information includes:

- Your company name and address (this should preprinted from the laboratory)
- Grower Name
- Sample Identification
- Crop and yield goals
- Previous crop
- Desired test options

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