Interaction of Planting Systems and Management Inputs for Soybean Production in the Mississippi Delta.

Soybean production has been studies from many angles over the last four decades with a major shift from planting in May and June to the Early Soybean Production System (ESPS) and planting in March and April. Soybean grain production has grown from less than 20 bu/acre to irrigated yields approaching 100 bu/acre with a state average over 50 bu/acre. In the same time frame, irrigation has become a common practice along with twin-row planting (TR, two rows on the same bed). In an effort to evaluate input costs while maintaining profitability, a multi-year project was funded through the Mississippi Soybean Promotion Board to study various inputs including planting pattern and seeding rates (whole plots) and various other practices (subplots) that are used routinely without much prior knowledge. These included fungicide, desiccation, P and K, and/or N and S. The treatments were arranged in a split plot design with four replications with two studies at the Delta Research and Extension Center (DREC, Irrigated) and two additional at the North Mississippi Research and Extension Center (NMREC, Rainfed). This poster will only cover the DREC Irrigated location. Twin-row (TR) and single-row (SR) planting at either 8 or 12 seed/ft were established as a 2x2 factorial whole plot. A stepwise approach was then used to include fungicide (yes or no); desiccation (yes or no), P-K fertilizer (0 lb/acre or 100 lb P2O5 and 100 lb K2O/acre); and N-S fertilizer (0 or 100 lb AS/acre). Grain yields were determined by harvesting the center two rows with a plot combine and retrieving a grad sample for determining harvest moisture, bushel test weight, and Seed Index (100-seed weight). Results indicated no response to fertilizer with soil tests indicating no need for fertilizer. Fungicide applications should be made only after shouting while desiccation depends on the season.