EFFECTS OF P APPLICATION RATE AND FREQUENCY ON P ADSORPTION AND WATER EXTRACTABLE P IN A MEADOW BROWN SOIL OVER 12-YEAR FIELD MICRO-PLOT TRIALS

摘要

Long term P fertilization increases the water extract-able P (WEP) thus increasing P loss risk. Distribution dynamics of WEP are known to promote the management of P fertilizer and prevent the pollution of surface and ground water. An experiment with meadow brown soil was therefore conducted from 1997 to 2008 in field micro-plots conditions. The effects of P application frequency and rate on WEP and P adsorption capacity was investigated with four fertilization methods: unfertilized control, N fertilization annually, N plus P fertilization annually, and N fertilization annually plus P fertilization once every 6 years. Long term P application increased the WEP contents thus increased the risk of P loss from soil into surface and ground water. P application frequency had a significant impact on the WEP. Specifically, contents of WEP gradually increased over time with annual P application, while they decreased with P applied once every 6 years in each 6-year period. At the end of each 6 years period, the higher WEP concentrations with annual P application indicated that P fertilizer should be applied once every 6 years to decrease P loss risk in the long term. The higher P adsorption capacity with P application once every 6 years confirmed that P fertilizer should be applied once every 6 years for agro-environment safety.