Growing Corn with Less Nitrogen

The St. Clair District Soil and Crop Improvement Association ran a nitrogen project for five years from 2000 to 2004. A total of 44 plots were established. The project cooperators set up nitrogen rate strips in their fields. There were several nitrogen rates below their normal rate of nitrogen and one above the normal rate. The rates were used to determine the maximum economic rate of nitrogen (MERN) for the field.

The weather had its usual affect on the plots, so some yield data was not useful. There were about 25 plots where the MERN could be calculated. The MERN was within 14 lbs. N/ac of the cooperator’s normal rate of nitrogen on five of the 25 plots. On ten of the 25 plots the cooperator had the opportunity to reduce nitrogen rates by 30 to 65 lbs. of nitrogen without reducing income on the field (refer to Table 1). Four of the remaining 10 cooperators had the potential to reduce the nitrogen rate on their field by 70 to 85 lbs. The other six cooperators had manure and/or red clover in the rotation and were able to reduce nitrogen rates 70 to 180 lbs of nitrogen per acre from their normal rate of nitrogen (refer to Table 2). In two cases the manure was able to supply the entire nitrogen requirement for the crop.

All growers apply an adequate rate of nitrogen to their field (except for the occasional mistake). In most cases there is some insurance built into the rate. With many growers, especially those who practice good soil management and have a good crop rotation, there is an opportunity to reduce nitrogen rates without having a significant impact on yield.