Abstract: A pot experiment was conducted to study the effects of controlled-release N and K fertilizers on mauls seedlings growth, their P and K use efficiency, and the N balance in soil-plant system. The results showed that the nutrient release from controlled-release fertilizers accorded well with the nutrient requirement of mauls seedlings. Controlled-release N fertilizer significantly increased the K use efficiency, and controlled-release K fertilizer significantly increased the N use efficiency. Under the same K application rate, the plant height and stem diameter under the application of controlled-release N fertilizer (CN) and controlled-release N and K fertilizers (NK) had no significant difference, while those under the application of common fertilizer (SF) were all higher. The plant dry mass and the P and K use efficiency were in the order of NK＞CN＞SF. Under the application of NK, the application rate of K had no significant effects on the plant height and stem diameter, but significantly affected the plant dry mass. The P use efficiency increased with increasing application rate of controlled-release K fertilizer, but was less affected by application rate common K fertilizer. The K use efficiency decreased with increasing application rate of K. The N use efficiency was in the order of NK＞CN＞SF, while the N-loss rate was in adverse. The residual rate of NK and CN had no significant difference, but was higher than that of SF. The application rate of controlled-release K fertilizer had significant effects on the N use efficiency and N loss rate, but no significant effects on N residual rate.

Key words: controlled-release fertilizer, interaction, N：K ratio, mauls, site type, site index, quantification theory I, nonlinear mixed model, plantation.