Starter Fertilizer Management for Corn and Soybean in the Southern Plains.

The increasing number of acres planted to corn (Zea mays L.) and soybean (Glycine max L.) in the Southern Plains, along with the increasing acres of no-till has raised questions about the need for starter fertilizers in these systems. Early plant growth and grain yield may be lower in no-till crops than in conventionally tilled crops due to the nutrient level in the root-zone. Objectives are to evaluate the effects of various starter nitrogen fertilizer placements and rates on full season corn and soybean in Oklahoma. The corn and soybean experiment consists of 3 placement methods (in-furrow, 2x2, and 2x4) and 17 fertilizer treatments. The corn in-furrow treatments consisted of 11, 22, and 45 kg N ha^-1. In addition to these treatments were Zn, S, and Zn plus S treatments that were added to 11 kg N ha^-1. The N was balanced to 168 kg ha^-1 on all in-furrow corn treatments by broadcasting urea. Another corn treatment consisted of broadcasting 168 kg N ha^-1 of urea. The corn 2x2 treatments received N rates of 101, 135, and 168 kg ha^-1. The corn 2x4 treatments received N rates of 135, and 168 kg ha^-1. The soybean in-furrow treatments received an N rate of 5 kg ha^-1. The soybean 2x2 treatments received N rates of 11, 22, and 34kg ha^-1. An additional soybean 2x2 treatment was N with Zn, and S. The in-furrow placement of starter fertilizer rates up to 22 kg N ha^-1 in corn may increase grain yield because of the early increased biomass and the higher nutrient uptake. The soybean trial in Miami, OK showed that 5 kg ha^-1 in-furrow treatment may decrease stand counts because the salt and ammonia toxicity injures the seedling.