Nitrogen, phosphorus and potassium cycling and balance in farmland ecosystem at the piedmont of Taihang
华北太行山前平原农田生态系统中氮、磷、钾循环与平衡研究

The feature and change trend of N, P and K cycling and balance in farmland ecosystem of Luancheng County at the piedmont of Taihang were analyzed. The status of nutrient balance was appraised, and the rational way to apply fertilizer was put forward. The result indicated that N balance went through a process from slight deficit to surplus during 1985-2000, changing from deficit of 1.4% in 1985 to surplus of 48.6% in 2000. Potassium balance changed gradually from serious deficit of 82% to slight surplus of 4.6%, but was still deficit in many fields. P budget was surplus ever since 1985. Comparing with the output of nutrients, the inputs of N and P were excessive, but the K input was short. Under the current soil fertility and crop planting structure, the countermeasure to control the application amount of N and P and to increase the application rate of K should be carried out, so that, there would be no significant surplus N emitting or leaching from soil into environment. The technique to return crop straw into farmland should be extended to increase the nutrient recycling rate.