A 2-year field experiment was conducted in North China Plain to determine the spatio-temporal variability of available N, P and K in ochric aquic cambosols,and to evaluate the effect of available nutrients on crop yield. The results showed that the content of hydrolyzable N tended to increase, the content of available K was relatively high but tended to decrease gradually with time, and the level of available P was very low and showed a high spatial variation. It was suggested that site-specific fertilizer management rather than traditional fertilization be adopted so as to improve the spatio-temporal variability of soil available nutrients. |