Nutrient sprays applied to the foliage of narrow-leafed lupins (Lupinus angustifolius L.) during flowering and podding do not increase seed yield

Abstract

Nitrogen (N), phosphorus (P), potassium (K), sulfur (S), manganese (Mn), magnesium (Mg), and boron (B) were applied as foliar sprays to narrow-leafed lupins (Lupinus angustifolius L. cv. Gungunu) grown in Esperance in 1991 and 1992. Applied individually, no nutrient increased the seed yield of lupins. In 1992, the application of 15 kg N/ha at 2 growth stages [flowering and 2 weeks after flowering (2WAF)I and 4 kg S/ha at 2WAF reduced the seed yield by about 10% (300 kg/ha), despite no evidence of damage to the foliage of the lupins. Nutrient mixes of N, P, K, S, and B were applied in both years at 3 growth stages (flowering, 2WAF, 6WAF), and no combination at any time of application increased the seed yield. In 1992, one combination treatment of (kg/ha) 15 N, 8 P, 12 K, 4 S, and 1 Mn applied 2 weeks before the start of flowering reduced yield by 14%. Where no foliar nutrients were applied, seed yields (t/ha) were 2.6 in 1991 and 3.2 in 1992. Foliar-applied nutrients sprayed during flowering and podding, in addition to some fertilisers applied to soil at seeding, are unlikely to increase the seed yield of lupin crops in the south coastal districts of Western Australia.