Phosphorus leaching risk assessment with manure fertilizer application in south China.

To investigate the phosphorus (P) leaching risk caused by applying manure fertilizer, six different manure fertilizers, namely, 0 (CK), 3,000 (F200), 4,500 (F300), 7,500 (F500), 10,500 (F700), and 15,000 kg ha(-2) (F1000), were applied to the surface soil (0-20 cm) prior to vegetable planting. The maximum Olsen P decreased with increasing amounts of the manure fertilizer. Total P did not change with treatments below 7,500, but decreased in the higher manure treatments. Water dissolved P (WDP) was highest in the upper (0-20 cm soil) layer, intermediate in the middle (20-40 cm soil) layer, and lowest in the lower (40-60 cm soil) layer. The 7,500, 10,500, and 15,000 treatments increased the WDPs in both the middle and lower soil layers and enhanced the degree of P saturation in the lower layer. This indicates that vertical leachate movement of P accumulation in the middle soil layer may be underestimated and the P leaching risk is enhanced using manure fertilizer levels >7,500 kg ha(-2).