Effects of Soil and Row-Spacing on Seed Chemical Composition and Mineral Nutrition in Soybean in the Midsouth USA.

Information on the effects of row-type, row-spacing, seeding rate, soil-type on seed protein, oil, fatty acids, sugars and mineral nutrition under the Early Soybean Production System (ESP) in the Midsouth USA is limited. The objective of this research was to investigate the effects of these agricultural practices on seed chemical composition. Two field experiments were conducted; one experiment was conducted in 2009 and 2010, and the other in 2008, 2009, and 2010 under irrigated conditions. Soybean were grown on 102 cm single-rows and on 25 cm twin-rows with 102 cm centers at seeding rates of 20, 30, 40, and 50 seeds m^–2. Soybean cultivars, 94M80 with earlier maturity and GP 533 with later maturity, were used. Results showed that increasing seeding rate resulted in increases of protein, sucrose, glucose, raffinose, B, and P concentrations on both single- and twin-rows. At the higher rates (40 and 50 seeds m^–2), this increase became either constant or declined. Protein and linolenic acid concentrations were higher in GP 533 than in 94M80, but oil and oleic acid concentrations were higher in 94M80 than GP 533 due to genotype differences and the inverse relationships between these seed chemical composition components. In 2010, there was no clear response trend of seed nutrients to seeding rate in both cultivars. The current research showed that row-type and seeding rate can alter seed chemical composition under clay and sandy soils, especially under high heat and drought conditions. This information is useful to soybean growers for optimizing agricultural practices to improve higher seed nutrition as sucrose, glucose, and fructose are desirable traits for soybean seed nutrition and taste.