Leaching and fractionation of phosphorus in intensive greenhouse vegetable production soils.

Abstract

Greenhouse vegetable production systems use excessive phosphorus (P) fertilizer. This study is set out to look into the P fractionation, mobility, and risk of P leaching in ten greenhouse soils. The mean P concentrations in leachates varied from 0.4 to 1.6 mg l-1 (mean of 30 days of soil leaching). Between 5.7 and 31.0 mg kg-1 of P was leached from soils during 30 days of column leaching. Organic matter (OM) and Olsen-extractable P (Olsen P) correlated strongly with cumulative P leached after 5, 10, 15, 20, 25, and 30 days of leaching. The high correlation between OM and Olsen P with cumulative P leached at 5 days of leaching suggests that in future leaching experiments, the leaching period should be extended to 5 days of leaching. The first two P fractions correlated significantly with the total P leached in the primary days of leaching. The pH had little effect on P leaching but had a significant impact on soluble and exchangeable P fraction, suggesting that P mobility would increase in these calcareous greenhouse vegetable soils as pH rose. The calculated change point (194 mg kg-1) was high, indicating that a high percentage (40%) of the studied greenhouse soils had exceeded the change point. In conclusion, due to the high degree of P saturation and change point in greenhouse vegetable soils, P mobilization is a significant risk, and the findings can be used to provide future direction for fertilizing greenhouse vegetable soils.