Abstract:In the middle ages of 1970’s,Northwestern institute of soil and water conservation carried out scientific inves-tigation and started long term field experiement and demonstration in arid hilly area of the south Ningxia under thesupport of Chinese goverment. Based on deep and systematic studies, from the policy of production construction topractical technology of efficient agriculture, followsnig comprehensive development strategies and technologicalmeasures have been proposed:″planting grass and shrub at first″,″fundmental way out lyiny in fertilizer,″to opti-maze agricultural structure″,″systems increasing crop yield of arid areas, ″techniques of orchard establishrnentwhich produce. abundant yeild and preduce fruitearlier with water saving in the production.″The factors of waterscience and technology and material input shortage have been three great inhabitors to develope efficient agriculturein this area,especially the lack of qualified scientixts and technicians andfunds. Therefore,to take developingstrategies such as considering overall situatio,making overall plans and considering all factors,solving key prob-lems, promoting gradually and so on,to pursue techniques increasing yield efficiently and practically to developemain industrial and to cultivate market economy will be significant to develope economy rapidly.

Abstract:This paper chiefly carry out the probe and study to the background, characteristics and development ways ofsmall watershed economy of water and soil conservation in our country. The main purposes are to summary success-ful experiences and theories of soil and water conservation of small watershed economic activities in order to make itsuit socialism market economic development and realize the aim of comfortable off level.

Abstract:The paper says that the work of soil and water conservation on loess plateau has been entering into a new peri-od with all-around, coordinative and stable development gradually since the eighties and also has formed a newstructure by taking a small watershed control as base,by taking stress control projects as the key at all levels and bytaking the key control to promote control development in a large seweale. The paper analyses the cause of formation ofthe structure from internal motive force of development and external environment conditions. It discusses the out-standing characteristics of the period macroly and summarizes the basic experiences over ten yearo briefly.It pointsout the exlsting problerns, too. To counter these problerns,the paper has put forward some relevant counter-mea-sures. These are mainly :To strengthen leadership further;To relax policies;To increase money,science and technol-ogy input;To implement the guiding principle of taking prevention as main conscientiously;To raise and enlarge keycontrol project at all levels enthusiastically; To break through the key point and to advance in all-around way. Thesense must be changed,Such things should be pushed forward in soil and water conservation work as developmentand management,developing commercial preduction, constructing small watershed economy and speeding up pacesof marching on towards comparatively well-off in rural area on loess plateau.

Abstract:In the paper we compared several formulas on the magnitude of concentration of monthly strem runoff and siltload within a year in 33 hydrological stations of tributaries of Yellow River in North Shaanxi Province. The reultsshiow there is a retoarked significance ralationship(α=0. 00 1 ) between Aggregation Index(Ag ), Gibbs-Martinsegregation Index(G. M),Degree of concentrationCn) and Uneven Distribution Coefficient(Cl )which representthe characteristcs of concentration of monthly precipitation,strem runoff and load. Among the four formulas it is themaxmum that variation coefficient and the range of maxmum and minimum of theDegre of concentration(Cn).There is a remarkable significance relationship between yearlyload modulus or yearly runoff and monthly Degree ofconcentration and it's peried of which calculated from vector composition of monthly runoff or load as a vector.So,wecan use the indexes of monthly concentration characteristics to analvxis the stream runoff and sediment vield andto plan approaches of soil and water conservation in a watershed and realignmet of runoff and sediment

Abstract:Two experiments both of simulation under rainproof shelter and plot in field have been done to study the yieldresponse of corn to different treatments of water supply in Non-irrigated Plateau of Loess. The results show that,inthe field simulation column experiment,the biomass and the grain yield of corn are increased parabalically with theincreaseL of the soil moisture or the total water consumption, but the crop water use efficiency is hyperbolically de-creased with the increase of the total water consurnption, In the field plot experiment,the grain yield of corn is in-creased parabalically with the increase of the total water consumption too, the minimal crop water efficiency can bernade in the dry treatment, but the maximal crop water use efficiency can be rnade in the treatment of low watersupply(i.e,,the irtigation quota is 70 mm per Mu),with the increase of the irrigation(quota,the soil water depletionis decreased,and the percent age of soil water depletion in total is exponentially decreased.

Abstract:Five techniques for measuring rainsplash were studied under the same condition using rainfall simulator.Theresults show that different rainsplash measurement methods significantly affect detachment amount;the metheds in- fluence greatly the relaitonship between splash detachment and time of exposure; when laboratory based method isused in the field.caution must be taken.

Abstract:To check the large area preserved by soil and water conservation measure is the bases to analyse and calculatethe benefits reducingrunoff and sediment by the measure. This paper has checked the true areas preserved byfourcontrol measures of terraces,flatland.forest.grass land in both 14 counties ofwest Shanxi praince and 8 counties ofeast Gansu province on the hilly and gully areil of loess plateau in the middle reaches of the Yellow River by use ofthe results of detailed land survey. The prexervation rata of each control measures has been obtained in broad regionin the above two types of area. The rate has been checked by the result of typical investigation in west Shanxiprovince.A realible basic data has been set for the study of benefits to reduce runoff and sediment by the controlrneasures in the middle reaches of the Yellow River.

Abstract:In this paper,soil moisture loss from terrance bank and its effects on crop yield were studied,based on themeassurement of soil moisture and crop yield on hilly,and gully region of North Shaanxi. The results indicated thatevaporation from terrance bank obviously affected soil moisture of the terrance land in lm from the bank, and theyield of per stem of crop reduced 18.2% compared to the slope land. According to the calculation,soil water of terrace landwith lm bank lost 10.9% and with 2m bank lost 11.2% compared to the slope land.

Abstract:Through the constructionf ecological agriculture with commodity economy,the agricultural economy may berapid developed and the work of soil and water conservation can be paid attention to the farmers. In this paragraph,it is analyed to the questions of the theory about the function of ecological agriculture with commodity economyand the division of period and i's characteristics for ecological agriculture with commdity economy in loessalplateau.

Abstract:This paper has taken Zigui county as an example. The inundated situation and the present situation of soil andwater loss of Sanxia engineering have been understood fully. That development of land resources influence on soiland water loss in arrangrnent areas of immigration and how to prevent soil and water loss have been thoughtdeeply.

Abstract:Shaanxi province is one of themost serious regions of soil and water loss in China,The soil and water loss leads to heavy sediment concentration in the rivers,the disasters of reservoir sedimentation are very serious.The reservoirsedimentation not only reduces the goals of multiple purpose development but also endangers the safety of the lifeand property of the people in the downstream. This paper elaborates the harmfulness of reservoir sedirnentation andits causes,and proposes the measures of prevention and cure.