ACCUMULATION AND REDISTRIBUTION OF MINERAL ELEMENTS IN COMMON VETCH DURING POD FILLING

Common vetch (Vicia sativa L.) is an annual legume used for hay and gr ain. Field studies were conducted during two growing seasons (1991-199 2 and 1992-1993) in a Mediterranean continental area of central Spain with the objectives of determining optimum harvest maturities for mine ral composition and redistribution patterns of nutrient elements durin g seed-filling. Maturity stages were defined as progressively higher D M concentration in the seed (full bloom and 200-250, 250-300, 350-450, 450-550, 600-700, 700-800, and >800 g kg(-1) seed DM. Concentrations of most mineral nutrients showed a decreasing trend with advancing mat urity. Maximum accumulation of N, P, Cu, and Zn was reached at the end of the period of rapid seed growth (450-550 g kg(-1) seed DM). These elements showed the greatest mobilization from vegetative structures, but did not supply the total needs for seed development during the pha se of rapid seed growth. Potassium, Ca, and Mn showed the lowest level of remobilization to the seed, with maximum accumulation at the begin ning of seed formation (200-250 g kg(-1) seed DM). In this case, remob ilization oversupplied the seed needs. When harvested for hay at the 4 50-550 g kg(-1) seed DM, common vetch can return 30% of accumulated K, Ca, and Mn to the soil in unharvested biomass. If harvested for grain at maturity (>800 g kg(-1) seed DM), only 30 to 40% of accumulated N, P, Cu, and Zn remained in the crop residue; however, 75 to 95% of acc umulated K, Ca, Mg, Fe, and Mn remained. Both individual mineral nutri ents accumulation-redistribution patterns and diverse uses of the aeri al biomass must be considered in assessing common vetch mineral nutrie nt needs.