Why soil test? What is soil testing? Collecting soil samples Plant analysis

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1 Why soil test? What is soil testing? Collecting soil samples Plant analysis

2 Soil testing is the only preplant method for diagnosing nutrient need Determines soil supply of plant nutrients and need for lime Provides information to make an informed decision Uses accepted methods that have been researched and tested Required for nutrient management planning Simple and accurate, but

3 Collect soil samples that are representative of a field or portion of a field Determine the nutrient need for economically profitable crop production Gain an understanding of nutrient variability within a field Monitor changes in nutrient status over time

4 Samples must be analyzed by a Wisconsin DATCP certified lab UW Soil and Plant Analysis Lab - Madison UW Soil and Forage Analysis Lab - Marshfield A & L Great Lakes, Inc. Fort Wayne, IN Ag Source Cooperative Services - Bonduel Dairyland Laboratories - Arcadia Mowers Soil Testing Plus, Inc. Toulon, IL Rock River Laboratory - Watertown Analyses must follow specified procedures UW recommendations

5 Soil testing is the measurement of a specific plant nutrient that has been extracted from a soil sample by mixing with a chemical solution These chemical solutions extract a fraction of the total nutrient, which is correlated with what is plant available Testing methods are routine and repeatable

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7 Relative Yield % Max Yield Extractable K (ppm)

8 Samples should be representative of the field UW Recommendations are for one sample every 5 acre (~ 470 x 470 ) cell Excessively high-testing P and K fields can be sampled on larger cells A minimum of 10 cores should be collected to the appropriate depth Collected soil should be mixed and place in a labeled bag For whole field sampling use a zig-zag pattern Record sampling information

9 Field characteristics Fields tested > 4 years ago; or Fields testing in responsive range Non-responsive fields tested 4 years ago Field size (acres) All fields Suggested number of samples 1 sample/ 5 acres samples/ field samples/ field samples/ field samples/ field samples/ field samples/ field Responsive range is where either soil test P or K are in the high (H) category or lower Non-responsive range is where both soil test P & K are in the very high (VH) or excessively high (EH) category

10 Types of sampling schemes Whole field Grid point Zone Scheme used is determined by: Expected fertilizer management approach Field average or variable-rate Sampling history Existing fertility level $$$$$ and time

11 Soil testing is the only preplant method of knowing nutrient need! WHAT SOIL TESTING TELLS US Crop N need Plant available P and K Crop P and K need Soil organic matter Soil ph and lime requirement Other tests if requested

12 Soil probe is most common for surface samples Bucket auger for very deep samples (rare in Wis.) Available from ag. supply companies and most county Extension offices

13 Label 4 Bags: OBS1, OBS2, OBS3, OBS4 -Collect the 10 cores for each -Mix in a clean bucket -Transfer ~1-2 cups to the proper bag -Fill out information sheet OBS1 OBS2 OBS3 OBS4

14 Don t sample non-uniform areas Wet spots, eroded knolls, steep areas, etc. If large enough sample separately and treat as a separate field Avoid Headlands, crop rows, dead or back furrows, areas where manure or stalks were stacked, field edges Sample depth depends on tillage Moldboard plow: Depth of plowing Chisel plow: ¾ depth of plowing No-till or similar: 6 7 in., include 0 2 in. sample for ph Be consistent sample to the same depth

15 NT NT CH CH SOIL ORGANIC MATTER (%) SOIL ph

16 LIME REQUIREMENT t/a NI ( target ph = 6.8) Depth Chisel No-Till

17 ph, P, & K tend to be higher in spring than fall Soil test levels rebound over time movement within the soil Fall sampling generally provides a more conservative (larger) fertilizer recommendation Most done in the fall (75 %) Be consistent with timing Sampling frozen ground is generally not a good idea Summer OK, but ground is often hard

18 Used where nutrients will be applied variably based on a computer generated prescription map Also can be useful if purchase/rent new ground and past history not well known Unaligned systematic grid point method 300 (2.1 acre) grid if both P & K are in non-responsive categories (VH & EH) 200 (0.92 acre) grid if either P or K are in responsive categories (below H) Considerably more expensive than Whole-field (cell) sampling

19 Sample locations have GPS coordinates Sample consists of at least 10 cores composited within a 10 radius of grid point Most utilize ATV with GPS tied to on-board computer

20 Used where management may be different across a field based on soil type, topography, crop history, or other identifiable characteristics Zone borders and/or sampling points can be georeferenced or can simply be flagged Plus/Minus Provides an assessment of variability better than whole field, not as good as grid A hybrid, but requires more thought and management

21 Sand Loam Limed 5 years ago Never limed Formerly 2 fields now all 1 field Muck 3 zones 2 zones 2 zones 15 T/a manure last year No manure 2 zones 3 zones Flat Poorly drained

22 If strips are 5 acres, sample each strip separately Use whole field sampling intensity guidelines If strips are < 5 acres and cropping & management histories are identical: Combine cores from 2 3 strips Fertilize similarly according to crop Grid sampling contour stripped field with the intention of spreading prescriptive fertilizer over the entire hillside is NOT appropriate

23 Another Suggestion for Larger Strips CELL SAMPLING PATTERN ALONG STRIP (60 x 150 ) SOIL TEST P

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25 Identify nutrient deficiency Determine nutrient shortages before they appear as symptoms Aid in determining Nutrient supplying capacity of the soil Need soil test and field history Effect of nutrient addition on the nutrient supply in the plant Study the relationship between nutrient status of plant and crop performance

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27 Growth (% of maximum) Deficiency % Reduction in Growth Luxury Consumption Critical Nutrient Range (no symptoms) Visual Symptoms Visual Symptoms Toxicity Concentration of Nutrient in Tissue (dry basis) Critical Concentration

28 Cell sap tests Usually in-field, quick tests, semi-quantitative Total analysis Lab tests on whole plant or specific part Sampled part may be dependent on growth stage Provides an indicator of plant nutritional status Assumes nutritional status is related to soil nutrient availability Include a soil sample

29 What to sample When to sample Sample handling Refrigerated (kept cold) Removal of contaminants (soil, dust, fertilizer) Interpretation

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