Water Budget Analysis of Red Soils in Central JiangxiProvince, China

The daily soil water budgets in the red soil areas of central Jiangxi Province, southern China, were investigatedwith a large-scale weighing lysimeter and runoff plots. From 1998 to 2000, peanuts (Arachis hypogaea L.) and rape(Brassica napus L.) were planted in the lysimeter and in 1999, peanuts were planted in the runoff plots. The soil waterbudget components including rainfall, runoff, percolation and evapotranspirat.ion were measured directly or calculated by Richards‘ equation and water balance equation. The results showed that most rainfall, including rainstorms, occurredfrom March to July, and induced the greatest soil water percolation during the year. The evapotranspiration was stilllarge from July to September when rainfall was ininimal. Thus, the lack of synchronization in soil water inputs and losseswas disadvantageous to crops growing in this region. Among the soil water losses, percolation was the largest, followed byevapotranspiration, and then soil runoff. Runoff was very small on farmland with crops. It was significantly different, fromthe uncultivated uplands where large-scale runoff was usually reported. The soil water storage fluctuated sinusoidally,with a large amplitude in the rainy season and a small amplitude in the dry season.