NUTRIENT CYCLING AND BALANCE OF SLOPING UPLAND ECOSYSTEMS ON RED SOIL
红壤旱坡地农田生态系统养分循环和平衡

Soil and water loss is an important way of nutrients loss.No tillage with mulching and ridge tillage can strongly decrease the loss of nutrients caused by surface runoff and soil erosion.The potential of nutrient loss through erosion is as follows:organic matter>total K>available K>total N>total P>hydrolysable N>available P.Strong leaching in upland of red soil is also an important way of nutrients loss,especially for N.The system with notillage and mulching has the largest surplus in comparison with other upland ecosystems.Soil nutrient level can be increased gradually when the nutrient balance is in surplus.Available P and K in soil would increase rapidly to a high level while total K decrease slightly.Total N,P and organic matter in soil increase,but they still have low content.There is a spatial variability of soil nutrients in agroforest ecosystems,soil nutrients in districts of agricultural crops have higher level than that in district of trees.