A comparison of the adaptation of yellow lupin (Lupinus luteus L.) and narrow-leafed lupin (L. angustifolius L.) to acid sandplain soils in low rainfall agricultural areas of Western Australia

Abstract

Almost the entire lupin industry of Western Australia is based on the single species Lupinus angustifolius L. (narrow-leafed lupin), which is very well adapted to coarse-textured, mildly acid soils. However, L. angustifolius is not well suited to the strongly acid sand plain soils along the low rainfall fringe of Western Australia’s agricultural areas, and alternative grain legume species may be preferable. These soils, known locally as wodjil soils, have very low nutrient contents, often high levels of extractable Al in the subsoil, and are common in areas where severe brown spot and root rot disease is caused byPleiochaeta setosa. Yellow lupin, Lupinus luteus L., may be a better species on these soils. This paper describes a series of trials comparing the grain yields of narrow-leafed lupin and yellow lupin on a range of soils in the agricultural areas of Western Australia. These trials were sown on a range of dates and in a range of rotational backgrounds between 1995 and 1998. With current cultivars, narrow-leafed lupin clearly has higher yield potential than yellow lupin when soil-extractable [Al] at a depth of 15–25 cm (measured in a 1 :5 extract of soil in 0.01 M CaCl2) is <10 mg/kg. When extractable [Al] at this depth is greater, yellow lupin can produce greater yields than narrow-leafed lupin, depending on other environmental characteristics, especially when extractable [Al] exceeds 28 mg/kg, but its yield advantage is often small. Yellow lupin is less sensitive to delayed sowing than narrow-leafed lupin, and more tolerant of brown spot, but narrow-leafed lupin is more responsive to good seasonal conditions and less sensitive to frost. We conclude that yellow lupin has a place in Western Australian farming systems on soils with >10 mg/kg extractable [Al] where these soils are in close lupin rotations, in areas where brown spot is severe, or in low rainfall areas where narrow-leafed lupin yield potential does not often exceed 1 t/ha on these soils. However, yellow lupin has had relatively little breeding effort in Australia and its place will remain precarious until better adapted, higher yielding cultivars become available.