Phosphorus forms and their distribution under long-term no tillage systems

Phosphorus (P) stratification in no-tillage (NT) systems has important implications for crop growth and potential P loss, but little is known about P forms and their distribution when mineral P fertilizers are placed to the depth of 5 cm in NT soil. A 10-year field experiment was used to study the effect of NT and mouldboard plough (MP) on soil P forms at three depths (0-5, 5-10 and 10-20 cm) and their relationship with Fe and Al oxides. The results indicated that stratification of organic P forms occurred under NT treatment, and Fe oxides may have a stronger capacity for adsorbing the P forms. When mineral P fertilizers were placed to the depth of 5 cm under NT treatment, there was no significant difference in P forms or crop yield between NT and MP treatment, and orthophosphate did not show any significant difference under NT treatment between 0-5 cm and 5-10 cm depth. Overall, the agricultural management practice that mineral P fertilizers are placed to the depth of 5 cm under NT treatment could result in stratification of P forms, while the changes in the distribution of P forms in soil profiles might help reduce potential P loss in surface runoff and do not make any difference to crop growth.