The Effect Of Different Agricultural Measures To Soil And Water Conservation Of Sloping Land In Yunnan

Yunnan is a typical mountainous province with low latitude and high altitude, with 84% land belonging to mountainous region. On the whole agricultural land of 2.84 × 10~6 hm2 in statistic, 71.06% of it is sloping lands with slope gradient over 14 %(8°), soil and water loss is a widespread problem in agricultural area because of the large proportion of sloping land and its improper use management.By the runoff location plot experiment at a sloping land with slope gradient of 26.05%(14.6°) in Yunnan, a study was carried out to compare the effects of three different agricultural measures, cropping systems, fertilization manner and contour hedgerow strip, which affected corn yield, soil and water loss, soil moisture content, benching process, gain and loss of soil nutrients. Main results were as follows:(1) In average, gradient 1.12% (0.64°) per year and 5.60%(3.20°) in total amount deceleration of five years were reduced by adopting integrative technologies of contour cropping, balanced fertilizers and hedgerow strip on the 9 meters length of slope land plot; gradient 0.46%(0.26°) per year and 2.28%(1.31°) five years were lowered only by up-and-down cropping, farmer's practice of fertilizer rates on the 30 meters length of slope land plot.(2) Respectively, soil moisture content 4.05% in top soil(0~20cm), 2.55% in subsoil(45~55cm) and 2.22% in lower subsoil(90~ 100cm) were increased by using integrative technologies of contour cropping, balanced fertilizers and hedgerow strip in comparison with up-and-down cropping, farmer's practice of fertilizer rates from May to October.(3) The contour hedgerow strip reduced over 97% of surface runoff and over 2.4 times of soil loss, 27.34% of surface runoff and over 1.7 times of soil loss was decreased by contour cropping maize, and 5.89% of surface runoff and 18.41% of soil loss was lowered by balanced fertilizers, integrating contour cropping maize with balanced fertilizers reduced over 2.0 times of soil loss.(4) The corn yield was increased over 15% by balance fertilizers, more than 9% by contour cropping and over 20% by contour planting hedgerow strip. The nitrogen input and output ratio of balanced fertilizers is in the range of 2.17 to 3.84, while the range of 5.31 to 7.17 is corresponding to farmer's practice of fertilizer rates.(5) The quantity of nitrogen and phosphate had more input than output while having notably less potash input than output on sloping land. The amount of nitrogen, phosphate and potash taken off by surface runoff had no obvious economic effect in agriculture, but large loss of soil nutrients caused mainly by soil erosion was a serious threat to sustainable agriculture, 43.81% nitrogen and 54.97% phosphate and 91.53% potash had been gone to waste due to soil loss in the total of nutrients loss taken from soil.(6) As a result of best control soil loss and surface runoff, and decreasing potash loss, ensuring high yield on sloping land, it is worthy to recommend farmers to conduct the ideal mode—integrated contour cropping and balance fertilizers and hedgerow strip with proper width in mountainous region.