SoilTesting FertRecommendations

Soil Testing, Fertilizer Recommendations and Wisconsin Nutrient Management PlanningKeith A. KellingDepartment of Soil ScienceUniversity of Wisconsin-Madison: 

Soil Testing, Fertilizer Recommendations and Wisconsin Nutrient Management Planning Keith A. Kelling Department of Soil Science University of Wisconsin-Madison

Topics to consider: 

Topics to consider Soil sampling a. objectives b. requirements 2. Soil testing a. approaches b. requirements c. UW program features d. reading a report e. certified labs

Minimum requirements: 

Minimum requirements Follow recommendations in UWEX Factsheet A2100 One recommendation per field * some exceptions * site specific is OK Field tested in last 4 years Each sample comprised of 10-20 cores Number of samples/field varies * sampling history * expected responsiveness

Needed intensity varies with:: 

Needed intensity varies with: Sampling history Expected Responsiveness - No samples in last 4 years, take 1 sample / 5 acres - Have samples – go to part 2 - If either P or K in high range or below, take 1 sample / 5 acres - If both P and K are VH or EH, use table

Recommended sample intensity for non-responsive fields tested within past 4 years: 

Recommended sample intensity for non-responsive fields tested within past 4 years * 10 cores/sample minimum

Multiple samples give better recommendations:: 

Multiple samples give better recommendations:

Small fields / contour strips with identical management / crop histories : 

Small fields / contour strips with identical management / crop histories

Specific sampling details in A2100: 

- proper tool Specific sampling details in A2100 - depth - pattern / place - frequency - special situations (tillage, SSM)

Slide11: 

Samples must be analyzed by a WDATCP certified lab - specified procedures - UW recommendations Analyzing samples

WDATCP certified labs, 2003: 

WDATCP certified labs, 2003 Ag Source – Bonduel A and L Great Lakes – Fort Wayne, IN Dairyland – Arcadia Rock River – Watertown UW Soil and Plant Analysis Lab – Madison UW Soil and Forage Lab – Marshfield

Slide13: 

Recommendations for nutrients must be consistent with UW recommendations Recommendations UW recommendations - Best estimate to optimize economic return - Not developed as environmental standard - Based on Wisconsin research on Wisconsin soils

Wisconsin “sufficiency” philosophy: 

Wisconsin “sufficiency” philosophy

Slide15: 

Wisconsin “sufficiency” recommendations Soil Test Level Interpretation Response * Phosphate (P2O5) Probability Recommended * For 160 bu/a

Other philosophies: 

Other philosophies Build-up / maintenance Cation balance / base saturation Crop fertilization Non-science based

UW Recommendations - Lime: 

UW Recommendations - Lime Examines target pH for each crop in rotation Recommends lime based on most acid-sensitive crop Lime recommended when pH more than 0.2 below target Indicate T/a of 60-69 and 80-89 lime needed to reach target pH

UW Recommendations – Lime: 

UW Recommendations – Lime Rotation 1 Rotation 2

UW Recommendations - Nitrogen: 

UW Recommendations - Nitrogen Optimum N rate similar for “Good” or “Bad” year. N use efficiency higher in “Good” year N need is a function of soil yield potential and environment Base N rate based on soil texture, OM, yield potential N in starter not counted (20 lb/a) Credits subtracted Assumes good management, small losses, little carryover

UW Recommendations – Nitrogen on Corn: 

UW Recommendations – Nitrogen on Corn Sands & loamy sands Other soils yield potential Organic Non- Very high matter Irrigated Irrigated Med/low /high -- % -- ------------------------- lb N/acre ------------------------

UW Recommendations – Nitrogen adjustments: 

UW Recommendations – Nitrogen adjustments Legume & manure N Tillage Soil N test (if done)

UW Recommendations – P and K: 

UW Recommendations – P and K Crop, soil and test specific P & K from soil and fertilizer feed the crop Recommendation considers - crop demand - soil test level present - soil type - yield goal

UW Recommendations – P and K: 

UW Recommendations – P and K ------------- ppm ---------------- Subgroup D Subgroup E

UW Recommendations – P and K: 

UW Recommendations – P and K 1. Consider crop – Determines demand level 2. Consider soil type – Determines subsoil fertilizer group 3. Consider soil test – Determines interp. range, chance of resp. 4. Consider yield goal – Determines relative nutrient need

UW Recommendations – P and K: 

UW Recommendations – P and K If soil test is optimum - Apply nutrients about equal to amount in harvested part of crop If soil test is L or VL - Apply amount for optimum plus amount to increase yield and slowly build If soil test is H or VH - Apply ½ or ¼ of amount removed in harvested part of crop If soil test is EH - Apply 0

Slide31: 

UW Soil Science Department