Nodulation failure is important in the poor growth of two lupin species on an alkaline soil

Abstract

This study examined the effects of inoculation of Bradyrhizobium sp. (Lupinus) on the nodulation and growth of 2 lupin species on an alkaline soil in the field. Plants of L. angustifolius cv. Gungurru (alkaline-sensitive) and L. pilosus Murr. P23030 (alkaline-tolerant) were either not inoculated or inoculated with Bradyrhizobium (strain WU425 or WSM1253) and grown on an alkaline clay, an acid loam, and a limed acid loam. On the alkaline soil, plants of both lupin species without inoculation nodulated poorly and had low nitrogen (N) concentrations in shoots. Inoculation with bradyrhizobia on the alkaline soil greatly increased nodulation and N concentrations in shoots, but nodule number of L. angustifolius was still lower than that on the acid soil. Lupin species differed in growth and nodulation on the alkaline soil, L. pilosus being more tolerant than L. angustifolius. Effects of liming on growth and nodulation were not significant. A survey of a farmer's crop of L. albus cv. Kiev mutant, adjacent to the field trial, showed that poor growth was associated with high soil pH and poor nodulation.