WHITE LUPIN UTILIZES SOIL-PHOSPHORUS THAT IS UNAVAILABLE TO SOYBEAN

White lupin (Lupinus albus L. var. Ultra) and soybean (Glycine max L. var. Elgin) were grown in an acidic soil low in available phosphorus (P) to investigate their different capacities to acquire soil phosphorus. Experiments done in the controlled environment of a biotron were supplemented with four separate greenhouse experiments. Lupin and soybean were grown in monoculture and intercropped on a soil with low available P that was labeled with carrier-free P-32 as phosphate. Lupin had significantly lower values of specific activity of P-32 and higher values of isotopically exchangeable P than soybean in all cases. The results show that lupin utilizes soil P from a normally non-labile pool of soil P that is not utilized by soybean.