Fertilizer practices in the fall
On short-term rented land having low to average test levels, it may not always be economically justified to apply P and K fertilizer at the buildup rates. Michigan soil test data has shown that nearly 70 percent of Michigan farm fields contain adequate P levels. However, only 20-25 percent of fields contain adequate K. Therefore, K may provide a higher return to investment compared to P fertilizer. Another economic consideration is to apply P and K first to fields that are most in need – below the critical level – and then allocate the remaining fertilizer to fields above the critical level.
Seasonality of fertilizer prices is another consideration. Purchasing fertilizer in the fall is generally cheaper compared to spring. The current trend in declining fertilizer prices is discussed in “Fertilizer prices continue to stumble.”
One drawback for fall P application is that the most common P fertilizers, diammonium phosphate (DAP) 18-46-0 and monoammonium phosphate (MAP) 11-52-0, have some nitrogen (N) in them. This N could readily convert to the nitrate form and lost from the root zone before being utilized by spring planted crops. Some of this N can be helpful to accelerate the decomposition of crop residues. Also, new granular fertilizer products are now available with multiple nutrients and flexibility in timing. Please consult with your fertilizer dealer about options available to you. For winter wheat, a small amount of N (25-30 pounds per acre) is recommended at fall planting to promote early vegetative growth.
The soil test should indicate if lime is needed to rectify soil pH. Fall offers the best opportunity to apply lime. It provides more time for lime to neutralize soil acidity. Long-term experiments in Michigan have shown that lime will improve nutrient availability and crop yield, and generate a good return for investment. Refer to MSU Extension Bulletin E1566, “Facts About Soil Acidity and Liming.” On rented land, the landowner and farmer should both agree on who will pay for liming, if needed. Correcting pH often resolves soil micronutrient deficiencies.
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