Study On The Soil Potassium Depletion And Rehabilitate In Jilin Province Corn Belt

Jilin maize zone lies in the middle of Jilin province, and the zonal soil are Black and Chernozem Soils in this area. Climate is suitable for growing maize: rain in hot season, high temperature and moist in summer , the high difference of the temperature between day and night, abundant solar energy and heat energy resources. Super add smooth and fertile land ,so it is suitable for growing maize and high and stable yield. Maize sown area in this area is about 200,000 hm~2, which covers the half of Crop Acreage in Jilin province, and is the main source of peasants' income in this area. At present. because of its superior natural conditions and advanced technology of maize planting, it becomes commodity grain base of maize and one of the three gold corn belts in the world. Potassium is not only one of essential macro nutrients for plant growth., but also is essential and unique monovalent cation for all the organism, and its physiological fuctions are not taken place by the other monovalent cations. However, because of the affluences of all kinds of natural factors and human's unreasonable uses of land resources, soil fertility appears degradation, especially potassium is reduced in different degree.This research selected 10 cultivated horizons of phaeozem that had a representatives from Jilin province, and ryegrass seedlings were grown uncessively for ten harvests to evaluate K in soil. And then, repaired the evaluated soil by simulated alternate drying-wetting flooding,constant humidity,alternate freezing and thawing specifically in northeast under natural conditions and the other physical methods, at same time, studied the change tendency of potassiume which applied potassium, the mixture of nitrogen and potassium, the mixture of potassiume and phosphorus, the mixture of phosphorus, nitrogen and potassiume, the mixture of potassium and corn stalk powder and the mixture of nitrogen, potassium, phosphorus and corn stalk powder.The result showed: (1)with the increase of planting stubble, the grow condition of ryegrass in the majority of soil became bad, but basic stable after 6 stubble. The amount of K uptaken by ryegrass reduced with the stubble increased. (2)Because of the absorption and utilization of ryegrass, available potassium in soil reduced gradually, when reduced till a certain level, it did not reduced or reduced lowly even successively painted, but the minimum of available potassium appeared. The minimum of Jilin is 30-50mg/kg ;(3)For the most of soil, the content of available potassium reduced gradually on the process of planting, only available potassium of three soil had relatively stable change tendency, which about 450mg/kg.This showed it was difficult to be exhausted to the minimum for the available potassium of black soil in Jilin maize zone. (4) Compare with the soil that did not apply potassium, available potassium and slowly available potassium also reduced. This showed the content of potassium in the soil will reduce if plants. With the passage of time, it will be depleted. So, we only slow down it by fertilizer.Analyzing linear correlation between the minimum of available k (x2)in soil and the content( x1) of available k in original soil,the content of exchangeable K,the content soil organic matter content,clay content and the cation exchange content, and had close relation with available k by DPS.The result of soil remediation showed all kinds of physical methods had no remarkable effect to repairing effect of available potassium in depletion Soil, but remarkable to exchangeable potassium. It meant all kinds of physical methods had very little effect to conversion reaction from slowly available k to exchangeable potassium. The result of soil remediation by all kinds of chemical methods showed: applied potassium could increased the content of water soluble potassium and exchangeable potassium and remarkably increased potassium supplying intensity in short time. But because of the increase of available potassium in the soil, the exchangeable potassium in the soil easily were fixed by soil colloid and not absorbed by crops. So we should apply potassium timely and proper quantity and improved soil fertility of potassium, thus realize the sustainable development of agriculture.