Nitrogen Management in Corn
In recent years we have had weather conditions that have been favorable for nitrogen loss in cornfields. In 1998, 1999 and 2001, significant rainfall during the spring contributed to nitrogen losses in several cornfields in the area, particularly in the river and creek bottoms. Nitrogen losses of over 100 pounds were measured in some fields. On sandy soils, nitrogen is more likely to leach or move down in the soil below the root zone. It is then unavailable to the corn plant and also contributes to polluting the groundwater. The use of a nitrogen stabilizer, such as N-Serve with nitrogen fertilizer, will keep the nitrogen in a less mobile form and reduce the risk of leaching. It is highly recommended on sandy soils, particularly if nitrogen is applied in the fall. Application of nitrogen in the spring pre-plant, may also reduce nitrogen losses. Sometimes this can be a challenge particularly if we have a wet spring. In our region we have more of a problem with poorly drained and saturated soils. This contributes to nitrogen losses from denitrification. This occurs when nitrate is converted to N2 gas in the soil and lost to the atmosphere. Side-dressing nitrogen when corn is 10 to 16 inches tall is the most efficient time to apply nitrogen, because nitrogen is being made readily available to the plant when its needs are greatest. Unfortunately wet weather and time limit the large-scale adoption of this practice. If you do not have yellow corn, it is probably nitrogen deficient. Application of nitrogen with high clearance equipment, even when corn is tassling, should provide an economic yield increase if soil moisture is adequate.
The first step in nitrogen management is taking a soil test. A soil profile nitrogen test will provide a good indication of the residual amount of nitrogen in the field. This test consists of sampling from the surface down to 6 inches and a second sampling from 6 inches to 24 inches deep. If nitrogen was applied in the fall and wet conditions may have contributed to nitrogen losses, it may be advisable to take a sample either pre-plant or pre-sidedress to determine nitrogen needs of your corn. Remember to give credit for a previous crop of soybeans or alfalfa, or an application of manure. You may be able to substantially reduce the amount of nitrogen needed for your corn crop. For more information on nitrogen management in corn, contact your local Extension office.