Studied On K Utilization In Purple Soil-wheat System Under Long-term Application

By comparison with routine fertilizer experiments, long-term fixed position experiments that is an important means by which cornfield ecosystem are studied have many advantages. It can study systematically changes of soil fertility, variant regularities of fertilizer efficiency; and overcome the effects of climatic variation on fertilizer efficiency; and study long-lastingly ^ systematically -, historically and evaluate scientially the problems on soil and rational application, such as soil nutrient balance, crop reactions to fertilizers, fertilizer application effects on soil fertility, rotation and application system etc; and provide the agricultural sustainable development with sciential decisions. Therefore, long-term fixed position fertilizer experiment is a focal points concerned and studied by soil scientists, soil ecologists and plant nutriologists all over the world. Although we have obtained some valuable data on long-term experiment in our country, but there are still more problems need to be studied. Purple soil is a special soil in the world and a peculiar soil resource in China. How do purple soil fertility change under long-term different application? The data about it are lack. It was short of studying on the variant regularity of soiK crop nutrient content and enzymatic activities in crop growth period under long-term application. Potassium is one of large nutrient elements that are necessary to plant growth and development, Lack K in soil will bring about crop yield decreasing. Water soluble K and exchangeable K are the activest parts in soil potassium rank. The rate and quantity of potassium translation between soil solid phase and liquid phase are decided by the K action means on soil solid surface, and it also decides the direction in which K fertilizer has gone and soil fixed K power. The studies on dynamic nature of potassium translation between soil solid phase and liquid phase have important theoretical and practical significances, because they will help us to know the cation nutrient action mechanism on soil solid surface and to rightly evaluate soil keeping and supplying K power. Kinetics of soil K+adsorbing-desorbing were studied fruitfully by predecessors, but it was shor* of studying on the changes of soil K adsorbing characters after long-term different application. How did potassium affect crop growth and development under long-term application? Whether was potassium balance kept in purple soil cornfield ecosystem under a rotation of rice and wheat? etc. The studies on the problems stated above were short. Therefore, in long-term fixed position experiment plots on the Purple Soil Fertility and Fertilizer Efficiency Monitored Base, the variation of purple soil fertility in rice-wheat rotation under ten-year different application, crop nutrient distribution and potassium utilization were studied in this paper by the means of fixed position observation, simulate experiment and chemical analysis etc. And the problems on application promoting soiK crop enzymatic activities, improving soil K+ adsorbing characters, reinforcing crop metabolism, raising crop quality etc. were deeply discussed. Lastly the purple soil K balance in the tenth rice-wheat rotation was also questioned. The results were as follows:1. A joint application of organic manure and chemical N^ P^ K fertilizer is more effective to maintain and raise the basic fertility in purple soil.(1)Combination applying organic manure and chemical N > P % K fertilizer(MNPK) is recommended to keep purple soil nutrient balance.The results of ten-year fixed position experiments showed that organic matter content of 0-20cra and 20~40cm two soil layers in the CK treatment decreased obviously. In all applying fertilizer treatments, especially the MNPK treatment, soil organic matter content of the two soil layers increased distinctly. In comparison with 1991, organic matter content of the two soil layers in the MNPK treatment in 2001 increased by 6. 44 g. kg"1 and 2. 82g. kg"1 respectively. Soil nitrogen fertility: Soil total...