Impacts of irrigation regimes on phosphorus leaching in manural loessial soil

Irrigation is one of the critical factors which influence leaching loss of phosphorus in soils. Effects of the 3 irrigation regimes (600、900 and 1200 m3/ha) on the leaching losses down to 120 cm soil depth were studied by using the refilled lysimeters. The results reveal that the phosphorus leaching losses were increased with the increase of irrigation amounts, and the leaching losses were increased obviously when soil Olsen-P reached to approximately 70 mg/kg. However, the P concentrations for all the tested P forms in the leachate were lowest under the highest irrigation amount. Under the inorganic phosphatic fertilizer plus diary manure application, phosphorus leaching was observed mainly in the form of dissolved phosphorus, and the proportions of total dissolved phosphorus to total phosphorus in the leachate were 66%, 72% and 75% under the 3 irrigation amounts, respectively. While, particulate phosphorus accounted for about 30% of the total leached P. Of the total dissolved phosphorus, both dissolved organic phosphorus and molybdate reactive phosphorus contributed about 50%. The better management of the phosphatic fertilizer plus organic manure disposal application with an optimizing irrigation amount would be an effective approach to prevent the phosphorus leaching loss from arable manural loessial soil.