Effect of applied phosphorus on the growth of Lupinus luteus, L. angustifolius and L. albus in acidic soils in the south-west of Western Australia

Phosphorus is the major nutrient element deficiency of grain legumes in the south-west of Western Australia. Lupinus angustifolius is the major grain legume grown on the acidic soils in Western Australia. However, L. luteus and L. albus are being researched as possible alternatives because of tolerance to diseases and specific soil type adaptation. The fertiliser phosphorus requirements of L. luteus and L. albus in acidic soils of Western Australia are not well known. By contrast, there is much information on the phosphorus requirements of L. angustifolius in these soils where placement of fertiliser phosphorus has been found to be important. Three field experiments were undertaken on different acidic soils in Western Australia (sand, sandy loam, and loamy sand) to compare how L. luteus cv. Teo and L. angustifolius cv. Merrit use fertiliser phosphorus, applied by different methods as superphosphate. Lupinus albus cv. Kiev Mutant, which is not adapted to the sandier soils, was included at the loamy sand site. In 2 experiments on the loamy soils, the phosphorus was either placed with the seed (drilled) or 8 cm below the seed while sowing seed at 5 cm (banded). In the experiment on sand, the phosphorus was either spread over the soil surface immediately in front of the seeding tines (topdressed) or banded below the seed. Compared with L. angustifolius: (i) for the 2 loamy soils, L. luteus used phosphorus more effectively for producing dried shoots, but was less effective at using phosphorus for producing seed (grain); (ii) for the loamy sand, L. albus was less effective at using the phosphorus for producing dried shoots and grain, except it was about equally effective for producing grain when the phosphorus was banded below the seed. For the sandy soil, L. luteus produced no grain yield response whereas L. angustifolius showed an about 20% yield response to the added phosphorus, and both methods of application were about equally effective. Phosphorus banded below the seed was more effective than phosphorus drilled with the seed for producing dried shoots and grain of L. albus on the loamy sand and for grain only of L. luteus on the sandy loam. Both methods of phosphorus application were about equally effective for producing dried shoots and grain of L. angustifolius and grain of L. luteus on the loamy sand. Fertiliser drilled with the seed was more effective than banded fertiliser for producing dried shoots and grain of L. angustifolius on the sandy loam and dried shoots of L. luteus on the loamy sand and sandy loam. The concentration of phosphorus in grain of L. luteus was consistently about double that found in grain of L. angustifolius. The concentration of manganese in dried shoots of L. albus was 3–5 times higher than in the other 2 species.