Nutrient mobilization and yield of soybean genotypes

Mobilization of nitrogen, phosphorus, and potassium from leaf and carpel tissue during seed growth was estimated for 18 diverse, field‐grown soybean lines and cultivars during two years. The objective was to determine whether lines differed in nutrient mobilization and, if so, whether such differences were related to yielding ability. Lines differed in nutrient concentration and tissue mass and in nutrient content, both at beginning of seed growth and at plant maturity. Mobilization from leaves and carpels potentially supplied up to 47, 23, and 29% of seed N, P, and K. Leaves were three to four times more important than carpels as sources of seed N and K and nearly twice as important as sources of P. Only mobilized leaf N exhibited a relationship with seed yield (r = 0.73∗∗ in 1978 and 0.43∗ in 1979). Leaf N mobilization was not heritable (correlation between years for line means was 0.09) in our environment, but might be more so under N‐stress conditions. The major determinant of mobilizable N was leaf mass at beginning of seed growth.