Mining soil phosphorus by zero P-application: an effective method to reduce the risk of P loading to surface water

This study aims to find field evidence for the effectiveness of P-mining to reduce the risk of P leaching to surface water. In 2002, a P-mining was conducted on four grassland sites in the Netherlands on sand (two sites), peat and clay soils. The mining plots received no P and an annual N surplus of 300 kg/ha/year. Grass was removed by mowing five to seven times a year. At the same sites, the effects of P surpluses varying between 0 and 40 P2O5 kg/ha/year were studied on adjacent plots. Soil samples were collected in late winter (before fertilizer application), early spring and in late autumn at depths of 0-5, 5-10, 10-20 and 20-30 cm and were analysed for total-P and molybdate reactive P (MRP), molybdate unreactive P (MUP - difference between total-P and MRP), water extractable P (PW) P-AL, NH4-oxalate extractable P (POX), Al (AlOX) and Fe (FeOX) and total-P. Mining soil phosphorus by zero P-application over a period of four years led to a strong (30-90%) reduction in both MRP and MUP concentrations in soil solution in the upper soil layer (0-5 cm). The reduction declined with depth and changes were generally not significant in the deeper soil layers. Mining also led to a decline in P pools in the soil solid phase. The largest decline was found in PW and P-AL, whereas reductions in more strongly bound POX and total-P were not significant