Corn Populations and Nitrogen Fertilization

Crop and Soil Environmental News, May 1999

M. M. Alley
W. G. Wysor Professor

Corn yield potentials are a function of the genetic yield potential of the hybrid, final plant population, fertilization to eliminate nutrient deficiencies, pest control, and climatic conditions for the specific site. The generally cool and dry April in most of Virginia has resulted in less than desirable corn populations in some fields. Although hybrid selection can not be changed and populations are less than desired, the yield potentials of these fields can be influenced by our sidedress N fertilization decisions. The following points should be considered as we determine the N fertilizer rate needed for each field:

1. Is the plant population adequate for high yields? If the population is adequate for high yields, apply N to reach the yield potential for the specific soil type.

2. Is the plant population less than the target population associated with high yields? In this situation, determine if the hybrid has "flex", "stretch", or "prolific" tendencies for increased yields per plant at lower populations. If the hybrid has the potential to increase yield per plant under lower populations, then adequate N fertilization needs to be provided to enable the crop to reach the yield potential for the specific soil.

3. Evaluate the yield potential for each field and each major soil type in larger fields. Research in our Cropping Systems project in 1998 showed yields varying from 104 bu/acre to 193 bu/acre in the same field due to differences in available moisture holding capacity between the two soil types. Changing sidedress N fertilizer rates between fields and large blocks of different soil types can be profitable and should be considered in this year when low crop prices require the highest possible yields from each field.

Nitrogen fertilization is a critical factor in corn production. Growers still have the opportunity in many fields to influence final yields and profits through application of the most appropriate sidedress N rate. In this difficult economic year, it is critical that we not miss any opportunity to enhance yields.

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