| Based on data of recent soil potassium analysis and the second general survey of soils in Gansu province, this paper studied the change of soil potassium in the cultivated farmland from the beginning of 1980's to 1996. The results showed that soils in the most area of Gansu have high supplying potassium po? tential. In addition, due to limited precipitation and less leach- ing, low intensive cropping, low yield and consumption, al- though little or no potassium fertilizer is added, and the potassi- um balance in farmand soils mainly depended on yard manure and stalks in the long term, the soils supplying potassium poten- tial in still high until recent. The analysis of 5,162 soil samples from the main 24 soil types in 33 counties of Gansu province indi- cated that average total K is 21. 52g/kg, and that readily avail- able K is 194. 94mg/kg, increased 5. 49mg/kg compared with the average value from the second general survey of the soils. Soil readily available K increased in Hexi corridor and Longdong re- gion where the input of nitrogen and phosphate fertilizer, the amount of organic manure and stalks application are relatively high, and small amount of chemical K was added. Soil readily available K decreased in Longzhong and Longnan region resulted from yard manure and little stalks application , especially K defi- ciency and potential K deficiency area is expanding in Longnan re- gion where the capacity of the soil potassium supply itself is rela- tively low, in addition rainfall led to leach. Soil readily available K keep balance in Gansu Province, but it reduced in 58% of the monitoring counties According to readily available K grade, pro- portion of samples less than 100mg/kg was rising, it showed that k deficiency and K potential deficiency area tent to expand. Field studies have been conducted on some economic crops response to potassium application in successive 3 years, sugar beet ,brewing barley, garlic and cotton in Hexi irrigation region rice and corn in Longnan region. The results showed that in- creasing production rate of K fertilizer to economic crops was above 50%, The yield of sugar beet and brewing barley increased 5. 6% and 6. 7%, respectively, k fertilizer also increased the sug- ar content in sugar beet. After application of K fertilizer, the yields of some vegetables in Baiying region ,and the rice and corn in Longnan region obviously improved. By applying the field trial results, NPK fertilizer patterns of sugar beet and brewing bar- ley have been set up, and good effects have been made in the demonstration. By the analysis of soil potassium balance and crop response to potash application, it was concluded that the farmland soils have strong supplying potassium potential and absorbing K pow- er in the most area of Gansu Province ; if potassium of agricul- tural wastes can be returned fields by cycle as much as possible, then the input and output of agricultural soil potassium will ap- pear small deficiency annually, but the capacity of soil potassium supply will not be decreased. So, in the respect of soil potassium fertility management in recent years, we should strengthen and attach importance to potassium recycle application in internal a- gricultural system, make full use of crop stalks and all kinds of resources of organic manure in practice. At present, adequate K fertilizer should be considered to ap... |
