Grid soil sampling for phosphorus and potassium can identify areas in fields with nutrient deficiencies and other areas with sufficient or excess nutrients. Nutrient maps can be used to define areas for manure application or exclusion, using supplemental fertilizer where manure is not applied or does not meet the crop requirements. The overall effect is to increase the fertilizer-replacement value of the manure, conserving its use for nutrient deficient fields and field areas. Related: LPELC Manure Nutrient Management
Before opening the case studies linked below, read the introduction "Grid Soil Sampling for Livestock Farms" and the "Case Features". Each of these case studies was conducted on a Minnesota farm and presents the method to:
The case studies do not discuss variable rate manure application, but do assume capability for supplemental fertilizer application, with or without variable rates.
Les Everett, Agronomist, University of Minnesota Water Resources Center email@example.com