Potassium balance and management on sloping land in southwest China

A study on potassium balance and management on sloping land was conducted in south Guizhou province of southwest China in 2000.In the trial,alley cropping,engineering terrace and contour planting combined with balanced fertilization were employed as the soil conservation measures to reduce potassium loss and keep a good K balance on slopping land,in comparison with the farmers' practice.Results showed that K balance on slopping land,beside fertilizer application and crop uptake,was related to rainfall,and runoff and soil erosion.Fertilization provided 89.66176.83 kg/ha total K to the soil annually making up more than 96% contribution to total K input in simplified soil K cycling.However,only 9.8%26.26% of total K from inorganic K was removed by crop uptake.Runoff and sediment had high content of readily available K which was 4.286.67 times of that in rainfall and 1.511.92 times of that in surface soil before erosion respectively.Soil erosion not only removed the readily available K brought on by precipitation(ranged 14.8223.1kg/ha),but also the readily available K in the soil(ranged from 4.469.35 kg/ha).Crops uptook 28.4690.10 kg/ha total K from soil.Intensive agricultural activities on sloping arable land caused severe soil slowly available K deficiency 175.34306.04 kg/(haa).Therefore,controlling water loss and soil erosion,returning crop residue to the field and using fertilizer efficiently are of great importance in maintaining potassium balance on sloping land.Alley cropping technology could significantly reduce runoff and sediment by 40.31%43.77% and 53.6%65.63%,respectively, compared with the local framer's traditional practice,and enhance readily available K concentration on top soil by 12.62%33.69% and inorganic fertilizer utilization efficiency by 26%.It is a good practice for potassium management on sloping land in southwest of China.