Performance of five soybean cultivars in relation to lime and phosphorus levels on an acid Ultisol

Abstract

The seed-yield response of five soybean cultivars (Hill, Geduld, Forrest, Welkom and Oribi) to applications of lime [Ca(OH)₂] and P was evaluated over two seasons in the field on an acid soil of the Normandien series (Plinthic Paleudult). As a result of a very dry first season, treatment effects were not clearly defined. However, seed-yield responses to soil P levels > 8 mg dm^-3 were not evident. Growing conditions during the second season were more favourable and highly significant lime × cultivar and P × cultivar interactions were observed. The relative performance of the cultivars in an unameliorated soil agreed with their ranking according to Al tolerance shown by seedlings in a previous laboratory study. Significant yield declines in the cultivar Forrest at the highest levels of lime and P were ascribed to a Zn imbalance in the plant.