| Tillage erosion is the soil to the uphill and downhill sports movement as farming tools and gravity Caused the displacement in slope farmland,the net amount of soil is transported,stacked,re-allocated to the downhill in the slope farmland.In fact,the tillage erosion as the underlying causes of serious soil erosion,an important form of soil erosion in the slope farmland andis the major component of soil erosion.Since the 20th century,the world has invested enormous energy research and soil erosion control work, the main object of concern is erosion caused by water and wind,while ignoring the tillage erosion.Southwest karst area and China's Loess Plateau area are the most prominent areas with poverty and environmental degradation,Karst,loess,desert and Cold desert are the tied for the China's four major areas of fragile ecological environment:Rocky desertification is the result of soil erosion,slope land reclamation is the major cause of accelerating soil erosion;tillage erdsion is a major erosion form of slope land.Therefore,the research of tillage erosion and farmland soil nature by it affected in karst area can provide for reliable evidence of the reasonable farming methods and farming tools,can help people to conectly understand the contributions of human activities on soil erosion,and there is important theoretical significance to rational use and protection of karst soil resources,combating rocky desertification. The research area of this paper locates in karst area of Zhongliang Mountain, Chongqing city.Tillage experiment plots are set up in different slope area,farmed by the area commonly used three tillage tools--shovel,hoe and trample-shovel,with downslope and contour tillage two ways,used grey small stones as the tracer.shovel and hoe downslope are set up 10 experiment plots,shovel and hoe downslope 6 experiment plots,trample-shovel downslope are set up 6 experiment plots,a total of 38 experimental plots.Select two sloping land without source of water and soil with the profile method for 137Cs Sampling,surveying the slope land average rate soil erosion for many years,used the tillage model by tillage experiment calculates the rate ot tillage erosion of two slope farmland,and seek the contribution of tillage erosion in total soil erosion.And excavated soil profile for the indoor measuring soil basic nature of the slope land different parts in the 137Cs samples,then sampling bamboo forest land,scrub land,grassland,garden,flat farmland,analysis the soil basic nature,comparative study on the impact of tillage erosion to soil's water conservation capacity,anti-erodibility and nutrients.Based on the study of tillage experiment,the results showed:The tracer recovery is 90.86%～99.85%,the average is 96.34%.High and stable recovery(96.34%,N=38) prove that this method of the present experimental study area tillage displacement is more reliable.After farming,the tracer in tracer district descends,but it remains high level in the entire farming path.With the increase of the slope gradient,the spatial distribution of tracer shows the following law:Tracer in the tracer district concentration less;the maximum tracer location farther and farther away from the baseline,and growing small;the movement of tracer along the tillage direction is becoming longer and longer distance.Such law of hoe and shovel downslope tillage is more visible manifestation than contour and trample-shovel downslope tillage.The mean soil displacement distance,soil translocation of hoe and shovel tillage are closely related to slope gradient,and they can be used to express linear equations. Accepting the implement design and handling effect,the mean soil displacement distance,soil translocation by trample-shovel downslope tillage is to have certain correlativity with soil moisture.The.soil displacement distance,of shovel downslope tillage is 5.67%bigger than hoe,and they part for are 8.30 times and 7.86 times of trample-shovel;Till the contour tillage,soil displacement distance of shovel is 1.3～3.8 times of hoe.Shovel mean soil displacement of downslope tillage is 2.01～2.40 times of contour tillage;the hoe's of downslope tillage is 3～8.76 times of contour tillage.The order Arousing.soil translocation is:downslope tillage＞shoveling downslope tillage＞shoveling contour tillage＞hoeing contour tillage＞trample-shovel downslope tillage.From tillage erosion,contour tillage methods obviously superior downslope tillage;and in downslope tillage the trample-shovel on the superior hoes and shovels. That karst area farming land breaks to pieces,the slope is comparative short is tillage erosion main cause.Based on the study of 137Cs tracer method on sloping farmland,the results showed:The soil erosion rate of two slope farmland is 2765t/(km2·a),3202t/(km2·a), the average 2984t/(km2·a);the tillage erosion rate of two sloping farmland is 2175t/ (km2·a),2354t/(km2·a),and their contribution to respective total erosion is 78.7%, 73.5%,average 76.1%.The top erosion rate of two research plots is greater than 10000 t/(km2·a),and is the strongest area in the slope farmland,the upper slope farmland erosion rate for 3009 to 4000 t/(km2·a)around,and heaping up in the lower part of slope farmland,it's opposite to non-slope farmland.The average of soil erosion is only 40.3%of slope farmland in Yungzi Plateau,39.9%of the Three Gorges reservoir area, 54.1%of Jia-ling River Basin,39.1%of Loess Plateau.It is-the basic characteristics of karst mountain area slope farmland,soil erosion that soil erosion is not large,but relatively strong.When the natural using type has been reclaimed slope land,there is no litter in the soil surface,the capacity of water storage and anti-corrosion greatly reduced;also the density of soil surface increase.After the reclamation slope farmland,the average non-capillary porosity of surface soil is larger than lawn and garden,saturated water storage capacity in relation to non-agricultural land,garden and flat land decreased by 38.31%,18.28%,19.05%,Soil non-capillary water storage capacity in relation to non-agricultural land and flat land decrease by 52.58%,38.52%;But also the entire soil profile(60cm)saturated water storage capacity reduce by 6.6%,the capacity of non-capillary water storage drop 44.3%.From the top to the foot of slope farmland the profile of water storage capacity of differentiation is:The capacity of saturated water storage and non-capillary water storage is gradually increasing,the gross capacity of the capillary water storage is gradually reduced.After reclamation slope land,the capacity of storage precipitation fell 50.4%,and it gradually increase from the top to the foot of slope farmland.Found the soil anti-erodibility of slope farmland increased with the indicators of inorganic clay and micro-aggregate type;and with the indicators of water stable aggregates evaluation,the results are contrary.Comparative study found that the inorganic clay-micro-aggregate indicators is not suitable for evaluation of soil anti-erodibility in karst areas,At least not suitable for evaluation of slope farmland.This may be related to special soil and the fragile ecological environment of karst areas.The average of＞5 mm water stable aggregates of slope land surface soil is only 16.07%of the non-agricultural land,28.5%of garden;The average is 13.92%of＞2mm water stable aggregates of slope land,and is 24.19%of non-agricultural land,23.64%of garden.After reclamation slope land,the content 1～0.25mm water stable aggregates increase in aggregate,the average is 16.2 times of non-agricultural of land.And the content of＞0.25 mm water stable aggregates is 66.52%of non-agricultural land.The content of＞5 mm,＞2mm and＞0.25 mm water stable aggregates arelow in the top and bottom of sloping land surface soil,higher in the upper and lower;And the 1～0.25 mm water stable aggregates content gradually increase from the top to foot.The＞5 mm aggregate destruction rate of slope farmland is 1.86 times of non-agriculural,1.28 times of garden;the＞2mm aggregate average destruction rate of slope land as high as 83.13%,is 2.5 times of non-agricultural,2.39 times of garden,the＞0.252mm aggregate average destruction rate of slope land is 39.15%,is 4.19 times of non-agricultural,3.9 times of garden.The destruction rate of＞5 mm,＞2mm and＞0.25 mm aggregates are higher in the top and bottom of sloping land surface soil,lower in the upper and lower.The average of water stable aggregate average weight diameter is 1.12 mm of Sloping land surface soil,it is 28.75%of non-agricultural,decline 65.78% than garden,higher 10%than plat land.The differentiation of water stable aggregates average weight diameter is the same as＞5 mm,＞2mm and＞0.25 mm water stable aggregates content in slope land.Compared to other used land types the soil organic matter,total N,available K of slope farmland decrease significantly;the total K and P is increased;Effective N,P changes in the more complex.The nutrient space differentiation by the impact of soil erbsion is clearin the slope farmland soil,nutrient decline in the pot and uphill due to soil erosion,accumulation more strongly in downhill than the foot of the slope land, however,the nutrient status is not as well as the foot,the foot is the elements Meeting of other slopeparts,Nutrients in the best;the differences of soil nutrient content between the bottom and surface is relatively small in the foot and downhill of the slope.By combining the special natural conditions in Karst mountain area,the impact of tillage erosion on the rocky desertification is discussed.put forward to strengthen the research necessity and important meanings of soil tillage erosion.
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