Cattle Manure Promotes Pod-Setting in Soybean.

Soybean yield is predominantly determined by the number of pods and seeds produced per unit area. Generally, soybean plants produce an abundance of floral buds, but the rates of flower and pod abscission/abortion in soybean were estimated to amount to 80%. Alleviation of this abortion rate should increase pod and seed number, and thereby increase yield. Previous studies revealed that cytokinin, which is synthesized in roots, has promotive effects on soybean pod formation, suggesting that improving physical and chemical properties of soil might enhance the synthesis of cytokinin in roots, and thereby promote pod setting. In this study, we attempted to modify physical and chemical properties of soil by applying different kinds of manure or chemical fertilizer and examined their effects on sink formation. Soil was mixed with five different kinds of manure or fertilizer (fast-acting nitrogen fertilizer, slow-acting nitrogen fertilizer, oil meal manure, cattle manure and "bokashi" compost). The long-raceme soybean genotype IX93-100 was grown in pot (10L), and physiological and growth responses were measured. Biomass production did not significantly vary with the kind of manure or fertilizer, but the number of pods was more markedly increased by the application of cattle manure than the other kinds of manure or fertilizer, suggesting that cattle manure has a promotive effect on sink formation in soybean. Further studies are needed to identify the ingredients of manure that might stimulate cytokinin synthesis and thereby pod setting in soybean.