Effect of seed phosphorus concentration, soil pH, and soil phosphorus status on the yield of white lupin

Previous research has suggested that successful establishment of narrow-leaf lupin (Lupinus angustifolius L.) in the field may be limited by low phosphorus (P) content of the seed. This relationship has not been evaluated for white lupin (Lupinus albus L.) and thus the primary objective of this study was to evaluate the effect of seed P concentration on the growth of a winter-hardy white lupin (cultivar, "Tifwhite-78"). A large pot study was conducted to evaluate the effects of lupin seed P concentration, soil pH and P fertilizer rate on the growth of white lupin. The study was conducted using an inherently acidic (pH 4.5), P infertile Troup loamy sand (loamy, siliceous, thermic, Grossarenic Kandiudult). Treatments included three lupin seed P concentrations (0.25, 0.43, and 0.91% P), two initial soil pH levels (4.5 and 6.5) and three rates of P fertilizer (0, 50, and 100 mg P kg(-1) soil). The test was conducted outside using pots having an inside diameter of 25.4 cm and a length of 67 cm and the plants were allowed to grow until physiological maturity. As expected, addition of P to this P deficient soil increased lupin seed yield, total dry matter production of shoots and roots, and the concentration of P in the various plant parts of the lupin plant. Results of this study show that lupin seed yields may be affected by the concentration of P in the planted seed, but only under high or optimum P fertility conditions. Soil pH had only minor effects on lupin seed and dry matter production. At the highest rate of applied P ( 100 mg P kg(-1)), slightly higher yields were observed at the lowest pH. Results of this study suggest that low seed P concentrations should have minimal effects on the growth and production of winter-hardy white lupin.