Differences among Lupinus species in field response to superphosphate

Abstract

Eight varieties from four lupin species were grown on a virgin lateritic soil with six rates of superphosphate, ranging from 0 to 1,792 kg ha-1. Dry matter yield and phosphorus and nitrogen contents of the tops were measured at about full flowering, together with days to flowering, pods set per primary inflorescence, and phosphorus and nitrogen contents of the mature seeds. All species gave sigmoid yield responses, reaching 90 per cent of maximum yield at superphosphate rates between 600 and 900 kg ha-l, depending on species. Varieties within species responded uniformly. The order of tolerance to deficiency was L. cosentini > L. luteus > L. angustifolius = L. albus. Tolerance was based on uptake rather than differing tissue requirement. Phosphorus and nitrogen concentrations in the seeds varied markedly with species, the rankings being L. luteus > L. cosentini = L. albus > L. angustifolios for phosphorus, and L. luteus > L. albus > L. angustifolius > L. cosentini for nitrogen. Superphosphate application caused parallel changes in phosphorus concentrations in the tops and seeds of each species. It slightly increased nitrogen concentrations in the tops, but not in the seeds.