Nitrogen Applications to Double-Crop Soybeans Following Wheat.

The purpose of my research project is to determine if applying nitrogen to double-crop soybeans before emergence following wheat increases the final yield of the soybean crop. I suspect that double-crop soybean yields are decreased by the presence of wheat residue. Wheat residue is relatively hard for the soil to break down and requires a large amount of soil nitrogen. Microbes in the soil use the soil’s nitrogen as an energy source in order to break down the wheat residue. This causes the nitrogen to be immobilized, preventing plants from obtaining it. This is the same nitrogen that soybean seedlings need in order to give them a strong start. At this point in the soybean seedlings’ life, the nitrogen-providing root nodules have not yet developed. The soybeans require nitrogen from the soil during these early stages until the nodules develop. By providing additional nitrogen, I suspect that the soil microbes will have enough nitrogen to break down the wheat residue without immobilizing all of the nitrogen that the soybean seedlings utilize at an early stage. By having this available nitrogen, the seedlings will have the ability to grow better until nodulation, which could result in additional yield. I will test this by applying multiple nitrogen rates to double-crop soybeans and comparing their yields to that of an untreated check. I will apply the nitrogen at rates that should hopefully show the highest rate that results in yield that provides an economic return. By applying nitrogen at an early stage to double-crop soybeans following wheat, the final yield of the soybeans will be increased due to decreased immobilization of soil nitrogen.