Phosphorus turnover in soil and its uptake by established Lolium perenne plants.
A technique is described for measuring the time-course of uptake of 32P from soil. Carrier-free 32P was applied to the soil of potted Lolium perenne cv. S23 plants, and the 32P content of leaves determined non-destructively every 1 or 2 days. When 32P uptake had almost ceased the plants were harvested and their total 32P content determined. Well-established plants took up 10-40% per day of the P in the soil labile pool. The transfer in the soil from labile to non-labile forms per day always exceeded this. Since the amount of P in the labile pool cannot have been changing rapidly, P transfer from non-labile to labile and from labile to non-labile forms must have been simultaneous and rapid. The half-time for P residence in the labile pool was about 1-2 days. The method has potential for studying P turnover and uptake in pots and in the field.