Adaptation of Lupinus angustifolius L. and L. pilosus Murr. to calcareous soils

Abstract

Current varieties of narrow-leafed lupin (Lupin angustifolius L.) are poorly adapted to alkaline and calcareous soils found commonly throughout the south-estern Australian cropping zone. Apot experiment compared the growth of Lupinus angustifolius cv. Gungurru with L. pilosus P20954 in a range of soils collected throughout South Australia. The soils displayed a range of texture (clay, 3–82%), pH (1:5 soil:H₂O, 7·0–9·6), and calcium carbonate content (CaCO₃, 0–47%). Potting mix (pH 5·8) was used as the control. The plants were grown for 7 weeks with weekly measurements of chlorosis score and leaf number. At harvest, dry weights were recorded and the youngest fully expanded leaves were analysed for nutrient concentrations.

The line P20954 grew much better in all the soils than Gungurru in terms of plant dry weight relative to the control soil, this being particularly evident in the calcareous soils. Chlorosis score correlated highly with shoot dry weight for Gungurru, but not for P20954. The main soil factor contributing to the chlorosis score of Gungurru was CaCO₃ content, whereas none of the soil factors significantly affected P20954, although in Weeks 2 and 3 chlorosis score correlated with CaCO₃ content. The dry weight of Gungurru was affected by a combination of factors including clay content, pH, and CaCO₃ content, whereas the dry weight of P20954 was affected by most of the soil factors measured. The dry weight of P20954 was positively correlated with aluminium and magnesium concentrations. Concentrations of all nutrients were above critical levels for both genotypes grown in all soils. The results indicate that L. pilosus has the potential to be grown in areas where current varieties of L. angustifolius are poorly adapted.