Should fertilizer nitrogen be applied after injected swine manure?
Many farmers question the nitrogen (N)-supplying power of animal manure and apply fertilizer N as insurance against yield losses. Precision farming trials in 2001 add new support for the conclusion that it is not profitable to apply such insurance N when liquid swine manure is injected into soil. The studies were made possible by funding from the Iowa Corn Promotion Board, the Iowa Soybean Promotion Board, and the Integrated Farm and Livestock Demonstration Program through the Iowa Department of Agriculture and Land Stewardship. Trials were conducted on fields where the manure was applied in accordance with the normal practice of the producer (Table 1). The manure was either knifed into the soil or applied to the surface and immediately covered by disks on the applicator. Fertilizer was applied in replicated strips going the lengths of the fields. These strips were at least two combine swaths wide. The fields were harvested with combines having yield monitors and global positioning sys
