A STUDY OF NUTRIENT BALANCE IN DIFFERENT CROPPING SYSTEMS ON A LATERITIC RED SOIL

The experiment in which six cropping systems was performed on a lateritic red soil were carried out from 1980 to 1984, on the campus of the South China Agricultural University, Results showed that the soil nitrogen, accumulated in all cropping systems, the ameunt of nitrogen increase in the doulle rice cropping system was low, whearas those systems includ-ing legumes, such as herbage mixed with murg bean and double cropped rice rosted with legume were the highest, the latter could increase about 150 kg/ha of nitrogen annually. Nitrogen accumulation in these systems was cue to higher efficiency of nitroyon fertilizer, and total soil nitrogen increased significantly.Phosphous balance of the soil showed deficit in all cropping systems, the effictercy of phosphorous fertilizer was low, about 1/3 of phosphorous fertilizer applied leaching to below the plow layer in most of the cropping systems.Patassium balance exhibited great deficit in the rice cropping systems. It was due to the considerable amount of K that leached tut under the sulmergeice cenditiers of rice culture the average amount reaching 44% of the potassium fertilizer applied. However, fer dryland cropping system, the potassium remained nearly in balance or showed increase, the soil potassium maintaining its original level after five years cultivation.It was demonstrated that the b(st way to maintain the N, K balance in the cropping systems was to incorporate rice straw and legume in the soil.