The growth of Lupinus species on alkaline soils

Abstract

Lupinus angustifolius L. grows poorly on alkaline soils, particularly those that are fine-textured. This poor growth has been attributed to high concentrations of bicarbonate, high clay content and/or iron deficiency. In field studies, we examined the growth of 13 lupin genotypes reliant on N2 fixation, or receiving NH4N03, at four sites with various combinations of soil pH and texture. Plants grown on an alkaline clay and an alkaline sand showed iron chlorosis at early stages, and had a slower shoot growth than those grown on an acid loam or an acid sand. Species varied greatly in the severity of iron chlorosis and also in growth and seed yield, with L. angustifolius, L. luteus and L. albus more affected than L. pilosus, L. atlanticus and L. cosentinii. Rankings of growth and seed yield of the lupin genotypes on the alkaline clay correlated well with the rankings on the alkaline sand soil. Plants which had severe iron chlorosis in alkaline clay also had severe chlorosis in alkaline sands. However, correlation between the severity of iron chlorosis and early shoot growth was poor. The results suggest that high pH and/or high bicarbonate are more likely than soil texture to be the primary factors restricting the growth of commercial lupins.