Wednesday, November 15, 2006

Starter Fertilizer Response of Corn on Soils with High Soil Test P.

S.C. Tingle, G.D. Binford, and D.J. Hansen. University of Delaware, 16483 County Seat Hwy, Georgetown, DE 19947

Delaware has a high percentage of soils that are high in soil test P due to long-term histories of poultry litter applications. Corn is a common crop that is grown on these soils, and this corn is often fertilized with starter fertilizer that contains P. The standard method of applying this starter fertilizer has been to place the fertilizer 5 cm to the side and 5 cm below the seed at planting. In addition to questions regarding starter P response on high P soils, there has been renewed interest in placing starter fertilizers directly on the seed (i.e., pop-up fertilizer). Our study had two objectives: to evaluate the likelihood of obtaining a response to starter P on soils high in soil test P and to evaluate the value of using pop-up fertilizers in corn. The starter treatments included no fertilizer, N fertilizer, and N plus P fertilizer. We measured early-season growth and grain yield responses. Early-season growth to starter fertilizer occurred often. The N fertilizer treatment usually resulted in small growth responses compared to no fertilizer, while the N plus P fertilizer treatment usually resulted in significantly greater growth responses than the N-only treatment. The pop-up fertilizer treatments usually resulted in greater early growth than no fertilizer but did not result in greater or faster early growth than standard starter fertilizer treatments. The N-only treatments often resulted in significant grain yield increases compared to no starter fertilizer, while the N plus P treatments seldom yielded more than N-only treatments. The pop-up fertilizer treatments did not yield more, and sometimes yielded significantly less, than standard starter fertilizer treatments.