The drought may have one beneficial side effect: Lack of rainfall can mean higher residual nitrogen levels in the soil. If rainfall between harvest and planting next year is not excessive, then carryover nitrogen from fertilizer applied this year could be available for next year's grain crops.

Researchers at the University of Nebraska-Lincoln Cooperative Extension Service suggests trying deep soil sampling for residual nitrogen next spring, two to three weeks before nitrogen-application time. They recommend choosing a dryland cornfield that yielded below the yield goal on which the 1988 nitrogen fertilizer rate was based. Potential leaching and denitrification between harvest and 1989 crop use will affect residual nitrogen levels, but according to annual tests conducted by the UN Soil Fertility Group, when crop yields are low due to drought conditions, high levels of nitrogen remain in the soil.

After drought caused substantially reduced yields in 1974, 1975, and 1976, the soil nitrogen level in the spring of 1977 was more than 250 pounds N per acre. In 1981, soil nitrates were high and no nitrogen was applied. Yields were 142 and 108 bushels per acre in 1977 and 1981, respectively. In both years, yields were no different than in other plots where nitrogen was applied.

Researchers recommend deep sampling for nitrogen on a routine basis. Sampling helps determine where deficiencies exist so that increased nitrogen can be applied to maintain yield levels; this drought year will provide additional incentive to test for higher residual nitrogen levels.