Loss of nitrogen, phosphorus, and potassium through crop harvests in agroecosystems of Qianjiang, Hubei province, PR China

The level of chemical fertilization in China is considerably higher than th at normally applied in Western countries. For example, in the last decade t he use of N-P-K chemical fertilizers increased, within the province of our study, from about 300 kg/ha in 1980 to about 850 kg/ha in 1990. Data on tot al amounts on nitrogen, phosphorus, and potassium that are removed with the harvest are necessary in determining and optimizing the amount of chemical fertilizers to be applied to different crops and in different cropping pat terns. In this article we report the results of analyses of N, P, and K con tent of soils and different parts of different plants (soybean, cotton, ric e, peanut, radish, Chinese cabbage, sesame, pepper, eggplant, and ambary) t ypically grown in rural areas of Southern China and provide an estimate of the balance of these nutrients under the five cropping systems that are dom inant in the studied area.