Root growth, nutrient uptake and yield of soybean cultivars grown in the field

Soybean (Glycine max L. Merr.) cultivars differ in their root morphology and their nutrient uptake capabilities. The relation between root growth, P and K uptake, and grain yield was investigated using eight cultivars grown in the field on Raub (Aquic Argiudoll) silt loam which received 49 kg P/ha and 93 kg K/ha. Hobbit (maturity group III, determinate) was among the highest in grain yield, P and K uptakes, and root system length. However, this cultivar was intermediate in its relative efficiency to utilize P and K to produce grain yield; among the most efficient cultivars were Asgrow 3127 (maturity group II) and Williams-79 (maturity group III). The hay cultivar, Wilson-6, was the least efficient. It was concluded that even though grain yield was correlated with nutrient uptake, selection for higher yields was not necessarily a selection for higher efficiency in utilization of fertilizer for grain production.