[Phosphorus behavior in soil-water system of paddy field and its environmental impact]

A field experiment with rice showed that P fertilizer application increased the concentrations of resin P in soil and total P in soil surface water, and both of them declined subsequently over time. Compared with applying mineral P fertilizer only, the integrated application of mineral-P and manure resulted in a higher resin P level within 20 days after P application. The total P concentration in soil surface water in the treatment of integrated application of mineral-P and manure was 3.4 times higher than that in the treatment of mineral-P fertilizer application only after 7 days of P application, and also, was 2.8 times higher than that in the treatment where P application rate was doubled. The potential of Ploss from surface water in the treatment of integrated application with manure was more than that in the treatment of applying-P fertilizer only. The effect of applied P sorts on P concentration in soil surface water could be ignored after 33 days of P application. Two drainages were conducted for rice growth, which caused the net P loss loading and its apparent P loss ratio in range of -0.038-0.076 kg.m-2 and 0.034-0.100%, respectively. To minimize P loss from rice production area, field drainage should be avoided in the initial week of P-fertilizer application or field harrowing.