Drought implications on fertilizer management

Because of reduced grain yield, farmers may be able to credit for some of the carryover phosphorus and potassium for the next year’s crops.

The drought will reduce crop yields this year (2012). Lower grain yield translates to reduced nutrient removal. Depending on the crop yield, you may be able to credit some of the carryover phosphorus (P) and potassium (K) in the soil towards the next year’s crop. If you are using MSU fertilizer recommendations and applied maintenance P and K according to a certain yield goal, then you will be able to account for the residual nutrients by simply subtracting the nutrients removed from nutrients applied. Please refer to the table below for Michigan nutrient removal rates.

Nutrient removal in harvest portion of several Michigan field crops.
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Nutrient removal rates table
Source: Nutrient Recommendations for Field Crops in Michigan, MSU Extension bulletin E-2904

Each field situation has to be treated differently because of varying soil test levels and expected yields. Also, if corn was harvested for silage instead of grain, then it is likely that more K was removed than the actual amount applied. These adjustments have to be factored in determining the fertilizer rate for the next year’s crop.

To take advantage of carryover nitrogen (N), P and K nutrients following a drought year, some farmers consider planting corn after corn. In Michigan, however, most of the soluble N may be lost from the rooting zone through winter and spring leaching, despite the fact that dry soils are able to absorb a lot of moisture before becoming saturated. Other risks associated with planting corn after corn are the reduced yield of the second year corn and potential buildup of pest populations.

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