Abstract:The loess Plateau is characterized dy serious water and soil eresion. The most active soil erosion is in the small watershed in which sediment production is concentrated. There are the significant differences in erosion patterns, erodibility and sediment production in various landform locations in the small watersheds. The better results can only be obtained by having a good grasp of the rules and adopting effective controlling measures. The xihe watershed is a small watershed with serious water and soil erosion in Guanzhong basin. Affected by the rising of the Lishan Mountain, soil erosion here is so serious that the bulk of sediments are carried into the reserviors, which not only reduces the storage capacity and economic returns but also threatens the lives and properties of the people in the lower reaches. Therefore, it is necessary to strengthen work on soil and water conservation in the small watersheds in order to reduce sediment deposited in the reservoirs.

Abstract:The effect of land slope upon the amount of the upslope, sideslope and downslope splash erosion was studied by using the simulated rainfall tests individually. The results indicated that the relation between the amount of the upslope and downslope splash erosion and land slope was roughly parabolic, and that when the critical slope was between 10°—15° and 20°—25°, but when i=2.037mm/min., the relation between the amount of sideslope splash erosion and land slope was a power function, and the critical slope disappeared, and that the relation detween the amount of downslope splash erosion and land slope was on the leaner increase, whose ascending rate increased with an increase in rainfall intensity. Finally, the multiple-factor equation of total amount of raindrop splash erosion, EI and land slope (S) was given in this paper, i. e. ST=5.985 (EI)^0.544S^0.471 where, ST——the total amount of solash erosion (g) per unit area E——raindrop kinetic energy (J/m²) I——rainfall intensity (mm/min.)

Abstract:This paper studied the process of soil erosion and nutrientl oss including organicmatter, total N and available P in the sloping lands through the lab artific ial rainfall, a-nd the effects of slope gradient and rainfall intensity upon the lossing process. It also analysed the process of soil erosion and nutrient loss of two treatemnts in the bare sloping lands and the net covering sloping lands. The results indica ted that the amount of nutrient loss went up with an increase in slope gradients and rainfallintensity, and that after the kinetic energy of raindrop was eliminated by the covering net in the experimental plot, the amount of soil and nutrient loss was reduced by 60% or so as compared to that in the bare sloping lands. The amount of nutrient loss was in the correlation with soil loss. The available nutrients in most of sediment sampes were higher than those in the soil with available P in particular.

Abstract:This paper describes the natural background of the kuyiehe, Tuweihe and Gusan-chuan River Watersheds, deals with the comprehensive control and development ofobjectives and tasks and also suggests various kinds of measures for the explorationand utilization of water resources, water and soil conservation, environmental protec-tion and the exploration and utilization, control and protection of the developing ar-eas of coalfields in these watersheds, At the same time, some important viewpointswere suggested on the guiding thinking, controlling strategies, developing layers andtotal layouts for the control and exploration of the key project, thereby the experien-cc and model were provided for the perfection of measures to develop and exploratehigh sediment producing areas.

Abstract:Limestone is widely distributed in Guangxi. Karst is well-developed. There are more rock mountains with more sloping lands with thin soil layer scattered. Soil formation is slow. The soil loss tolerance in the limestone area is only 68 T/km²·a, while the preseent soil loss in this region is 100—200T/km²·a, being much higher than soil loss tolerance. Based on the existing conditions in Guangxi, the author sug gested and discussed some water and soil conservation measures including: 1. afforestation; 2: enclosure of the hills for natural afforestation and vegetation recover; 3. construction of stone-bank terraces; 4. increasing application of chemical fertilizers and soil improvement by subsoiling; and 5. establishment of the eco-objective responsibility system.

Abstract:This paper analyses the rock properties, soil types, distributions and its physicaland chemical properties in the gneissose eroded area of western Henan province. Also, the multiple-point experiments were condcted in the gneissose severely-eroded area. The results indicated that such water and soil conservation measures as afforestation and water conservancy structures adopted can accelerate the process of soil formation and maturity, improve soil physical and chemical properties and soil fertility, and control soil erosion.

Abstract:¹³⁷Cs method was used to study soil erosion and sediment transportation in the farmlands on Mao (round loess mound) and slopes in North Shaanxi in this paper. A quantitative analysis was made of the erosion properties on Mao and slopes. The results indicated that erosion on Mao and slopes appeared to fluctuate very strongly, weakly, and very strongly again, and then weakly from the ups to the downs. Also, erosion equation for non-agricultural lands and agricultural lands has been used to calculate the modulus of erosion in non-agricultural lands on the Mao top since 1963, being 1 068 t/(km²·a), while the modulus of erosion in agricultural lands is 4059 t/(km²·a), Also, a comparative analysis was made of actual determined modulus of erosion of sloping farmlands in the runoff experimental fields on Liang (elongated loess mound) , Mao and slopes.

Abstract:The unified settlement of the problems of soil and water loss and water utilization is the base for doing a good work on the comprehensive control of soil and water erosion on the loess plateau. For this reason, it is necessary to search for the integrated points, the feasible approach and key measures to reduce soil and water loss, improve eco-environment and raise land productivity. This paper just discusses this problem and presents some existing problems and potentials in basic farmland construction and the improvement of rainfall water use efficiency.

Abstract:The authors made a survey of the disaster caused by heavy rainstorm occured on July 23, 1988(with a 300 year rainstorm frequency, precipitation in the center point was 210～240mm)in the hilly and gully regions in the east part of Gansu Province on the loess plateau. Based on the actual data, they analysed that this heavy rainstorm was formed by local geothermal convenction and initiated by the "人" -shaped shearing instability over 700 hpa. The heavy rainstorm only lasted from 2:05 to 2:35 in the morning, causing serious disaster. This paper analysed the natural and manmade causes of disasters caused by heavy rainstorm in the Yuan area. Also, it analysed the advantages and disadvantages of water and soil conservation engineering structures including stripe lands, gully head control works, reservoirs and dams as well as afforestation. Therefore, the idea of comprehensive control system of Yuan, slopes and gullies was presented, and it was suggested that the disaster resistant ability of water and soil conservation planning, design and construction should be improved since rainstorms characterized by heavey rainfall and great rain intensity are mostly caused by local geothermal convenction.

Abstract:The Loess Plateau is divided into 6 agro-ecological and economic systems in this paper. The authors analysed the productivity in each system from many aspects including land use structures, bio-community, productive value structure, energy flow and conversion efficiency in food chains, N-cycle in farmlands, crop water use efficiency as well as water and soil conservation benefits. Also, they proved their viewpoints with the typical examples, and pointed out the directions for the future development. It can be seen from the analysis of the existing conditions that the system of fruit, forests, agriculture and animal husbandry developed in Liang and hill area represented by Miaogou village in Yanan Municipality has the high economic returns owing to a large scale development of apple production, In 1990, per capita net income reached 166.7 Yuan, being 1.9 times higher than that in the surrounding villages. At present, one hectare orchard can support 6.7 persons, being 8.3 times higher than one hectare grassland supports. Up till to 1995, one hectare orchard can support 32.6 persons. In the system of fruit food crops, sideline production and animal husbandry formed in mound and hill area represented by Qianjiagou village in Mizhi county, the modulus of soil erosion has been reduced from 16,000 t/(km²·a). in the 1960s to 3,000 t/(km²·a ). at present owing to a large scale basic farmland construction and conversion of sloping lands into planting trees and grasses. In 1990, per capita net income was 656.4 yuan, being more than double that in the surrounding villages. At present one hectare orchard can support 14.3 persons, being 1.4 persons higher than that supported by one hectare cultivated with food crops. Up till to 1995, one hecgare orchard can support 28.5 persons.

Abstract:Land ridge is considered as the land resources in this paper. This paper deals with the utilization of land ridge in the central part of Sichuan Province that should be used to promote the economic development with forage crops as the core, and also to serve the establishment of water and soil conservation types of the vegetation network of farmland protection. Also, it deals with the role or position of mulberry trees in the utilization of land ridges, the principles of optimum vegetation structure, selection of plant species and factors affecting structure designs.

Abstract:The authors studied and analysed the growth conditions of vetiver grass in South China (18°10'N-20°10'N) and in North China (35°38'-36°33'N) as well as in the transitional belt through tests. The test results indicate that vetiver grass can grow and tiller normally in Taian in North China, thereby the introduction test of vetiver grass can be moved northwards by 9 latitudes.