EVALUATION OF CONVENTIONAL NITROGEN AND PHOSPHORUS FERTILIZATION AND POTENTIAL ENVIRONMENTAL RISK IN INTENSIVE ORCHARDS OF NORTH CHINA

Conventional practices of nitrogen (N) and phosphorus (P) application were evaluated based on nutrient balance calculation and soil N and P level from 916 surveyed orchards in North China, in order to assess the potential environmental risks. The results showed that excessive N and P application was common, with the average input rates of 588.4 kg N ha(-1), and 156.7 kg P ha(-1), respectively, which were 2.5-3.0 folds higher than the fruit N and P demand. High proportions of surplus N and P were found in grape, apple, pear and peach orchards in the plain regions with high economic returns. Nitrogen surplus reduced soil carbon (C)/N ratio in the plain, plateau and mountain regions. High soil Olsen-P level in the 40% of surveyed orchards, predominantly distributed in grape and peach orchards, was over the environmental threshold. Controlling N and P fertilization is the key to maintain sustainable fruit production in North China.