EFFECT OF STORAGE AND SIEVING ON THE PHOSPHORUS COMPOSITION OF SOIL SOLUTION

In this study, the effects of storage and sieving of a mineral soil (T ypic Fragiorthod) on the P chemistry of the soil solution have been qu antified. Intact and sieved soil cores were stored for 0, 1, 3, and 8 d at 4 degrees C prior to obtaining solutions, which were analyzed for total dissolved phosphorus (TDP), molybdate-reactive phosphorus (MRP) , dissolved organic phosphorus (DOP), and dissolved condensed phosphor us (DCP). Storage of both sieved and intact soil cores influenced the amount and chemical composition of P in solution. Concentrations of TD P, MRP, and DOP displayed a rapid decline with increase in storage tim e, whereas DCP concentrations, which were initially very low, increase d. Concentrations of TDP were significantly (P < 0.05) different betwe en solutions extracted from intact and sieved soils on the same day as sampling and this was accounted for by DOP and MRP, which were signif icantly (P < 0.05) larger in sieved soil. The proportions of MRP, DOP, and DCP were similar in solutions extracted from intact and sieved so ils on the same day, even for Day 0 where a large difference in TDP wa s apparent. The MRP fraction was consistently larger for intact cores (44%) than sieved (38%) on all days and varied little with length of s torage. The DOP component, which dominated initially, decreased with i ncrease in storage time, while DCP increased to become the major fract ion after 8 d of storage. This study has highlighted the potential eff ects of soil storage and sieving on the P concentration and compositio n of soil solution. The results also have important implications for s oil solution sampling and subsequent data interpretation.