MAXIMIZING SOYBEAN YIELDS GLYCINE MAX (L.) MERRIL

An experiment was designed to evaluate the effects of organic matter, foliar fertilization application, two systems of irrigation and the interactions of treatments on the growth and seed yield of three soybean varieties. The experiment was conducted for two consecutive years (1977, 1978) at the University of Nebraska Field Laboratory at Mead, Nebraska. The interactions of organic matter applications with irrigation and foliar fertilization increased yield. Apparently, the addition of organic matter to the soil improved the soil-water-root relationships which in turn increased seed yields. Irrigation increased yields 0.22 tons/ha over the non-irrigated check regardless of system used. The early (Amsoy 71) and full-season (Woodworth) varieties produced higher yields than the later maturity variety (Cutler 71). Foliar fertilization at one-half the suggested rate increased yields 0.11 tons/ha. However, the full fertilization rate caused excessive vegetative growth and subsequent lodging, so that yields were essentially equal to the non-fertilized check. Irrigation increased crude protein of the soybeans produced regardless of the method of application. As the rate of foliar fertilization increased, the level of seed protein increased, showing that foliar N and P were absorbed by the leaves and translocated into the seed. Only varieties showed differences in dry matter accumulation at all growth stages studied. However, each of the three varieties was highest in dry matter accumulation during at least one growth stage. Nitrogen content of the vegetative growth increased as the rate of fertilization increased. The nitrogen foliar applied was absorbed by the leaves and translocated to the other vegetative plant parts. There were varietal differences in N content. No relationship between N content and dry matter accumulation, N content and yield or dry matter accumulation and yield were observed