Specific and genotypic variation in the nutrient content of lupin species in soils of neutral and alkaline pH

Evaluation of the nutritional status, dry weights, and yields of genotypes of white lupin (Lupinus albus L.) and of the species L. pilosus Murr. and L . angustifolius L. were made in a field of mildly acidic (minimum pH 5.8; a ir-dried soil : water ratio 1:2.5) to alkaline (limed to a pH maximum of 8. 4) soil at IACR-Rothamsted, UK, during the 1997 growing season. Plants were sampled for shoot biomass and nutritional content during the season and se ed yield per plant. Lupinus pilosus was the species most tolerant of the calcareous soil, where as L. angustifolius was the least tolerant. Considerable variation in toler ance was apparent between the L. albus genotypes; the cultivar Lucyanne was comparable with L. angustifolius, whereas the genotypes La 673, 668, and 6 75 were more comparable with L. pilosus. Leaf chlorosis was shown to be an unreliable measure of calcareous soil tol erance in the field. A genotype soil-pH interaction in the expanded leaf nu mber indicated that this analysis might be of use in genotype evaluations. Nutrient concentration differences were apparent between the species and be tween the L. albus genotypes. This indicated the occurrence of possible tol erance mechanisms including the control of calcium uptake and the partition ing of iron. Clear differences were apparent between the three species in t erms of tolerance to the calcareous soil. Within L. albus important differe nces were apparent when specific analyses were examined. However, variation between different analyses and at different stages of growth resulted in t he differences, taken as a whole between the L. albus genotypes, not being of sufficient magnitude to discriminate potentially tolerant from susceptib le genotypes. The complexity of calcareous soil stress and the potential ap plication of the analyses for physiological studies and genotype screening are discussed.