Threshold Values on Phosphorous Leaching of Vegetable Soils in Fuzhou

Surface soils of vegetable plots in Fuzhou suburbs were sampled for this study. A simulated continuous leaching test on the soils was conducted to examine the soil-water phosphorus correlation. The results clearly indicated that CaCl2-P and organic P in the soil correlated very significantly to the concentration and accumulation of dissolved P (DTP). Thus, CaCl2-P and organic P were considered excellent indices for the risk evaluation on soil phosphorus leaching. At DTP concentration of 0.05 mg L-1 as the critical value for eutrophication, the CaCl2-P and organic P threshold values for phosphorus leaching in vegetable soils were 14.1 mg穔g-1 and 205.8 mg穔g-1, respectively. According to Hesketh (2000), the "change-point" concentration of the Olsen-P for the vegetable soils was determined to be 96.6 mg穔g-1.