Why Soil Test in The Fall?
Soil testing is a best practice recommended by Michigan State University Extension to achieve the desired agronomic, economic and environmental outcomes from fertilizer practices. Timing-wise, there are several advantages to soil test in the fall compared to spring.
There is more time available in the fall to collect soil samples and make fertilizer decisions compared to spring. Based on the soil analysis, fall season allows additional time to think about upcoming management decisions.
Farmers usually apply phosphorus (P) and potassium (K) fertilizer in the fall when there is more time and equipment available and soil compaction is less of a concern. This simplifies spring operations and streamlines planting. On soils with optimum fertility levels, field research has shown fall applications of P and K would be equally effective compared to a spring application prior to corn and soybean planting. For winter wheat, all the P and K requirements are best applied at fall planting.
Also, dry fertilizers can be safely and quickly applied in the fall. Some tillage will help ensure nutrients are placed below the soil surface. This will help reduce stratification and lower the concentration of dissolved P in the runoff water.