Yield and Composition of Field Bean and Adzuki Bean in Response to Irrigation, Compost, and Nitrogen 1

Abstract Nutritionists expect bean seed to provide a nutritious, high‐protein food. Consequently, production practices, that alter nutritive composition and yield, affect both human health and economic profit. Field bean ( Phaseolus vulgaris L.) and adzuki bean [ Vigna angularis (Willd.) Ohwi and Ohashi] were grown on Udorthentic Haploborolls, sandy, mixed soils in central Minnesota to measure the effects of irrigation, rhizobial inoculant, and N on seed yield, protein concentration, and nutritive value. Main plot treatments were rainfall of 16 to 36 cm during June, July, and August and rainfall plus irrigation of 24 to 30 cm. Subplot treatments for fieldbean were untreated, compost at 3 to 6 metric tons/ha, rhizobia, inorganic N at 74 to 310 kg/ha, soybean [ Glycine max (L.) Merr.] meal at 112 kg N/ha, corn ( Zea mays L.) grits plus inorganic N at 112 kg N/ha, and compost plus inorganic N. Subplot treatments for adzuki bean were untreated, rhizobia, and inorganic N at 112 kg/ba. Seed harvested from the treatments was analyzed by standard methods for amino acids, N, P, K, S, Ca, Mg, Fe, Zn, Mn, AI, B, Cu, Na, Mo, Ni, Pb, Cr, and Cd. Yield increases from irrigation ranged from 1,198 to 1,940 kg/ha. Yields from the subplot treatments differed significantly under irrigated but usually not under dryland treatment. Highest yields of fieldbean were obtained from compost plus inorganic N. The effect of compost on seed yield and quality was equivalent to that of 74 to 112 kg/ha of inorganic N fertilizer. Soybean meal, corn grits plus N, and N fertilizer treatments at equal rates of N did not differ in fieldbean yield or protein percentage. Irrigation resulted in low‐protein bean seed but compost and/or inorganic N at high rates usually maintained protein at acceptable levels. Amino acid composition of bean protein was not significantly affected by irrigation or other treatments. Bean seed from dryland plots was superior to seed from irrigated plots in protein and Zn concentrations. Nitrogen to protein conversion factors among treatments ranged from 6.19 to 6.26 for fieldbean and from 6.06 to 6.24 for adzuki bean.