Study on the Response of Soil Nutrient Content to Soil Loss in Karst Sloping Land of Southwest China

[ Objective] The study aimed to analyze the response of soil nutrient content to soil loss in karst sloping land of Southwest China. [Method] Choosing a karst sloping land in Nanchuan, Chongqing City as a sampling area, we analyzed the basic physical and chemical properties of soils at different sampling points, as well as the movement of Mg, Cu, Zn, Mg, Mo and Mn in the soils. [ Result] In the sloping land, there was a var- ying decrease in the content of all soil nutrients from the top to the bottom, but there was no obvious deposit at the bottom. In addition, Mg, Cu, Zn, Mg, Mo and Mn content had clear inflections in the sloping land, and these inflections mainly appeared at 15 -25 m. It proved that both surface soil erosion and underground soil leaching occurred at the same time in the karst sloping land. [Conclusion] The research could provide scientific references for the restoration of ecosystem in karst mountainous areas.

Study of Spatial and Temporal Processes of Soil Erosion on Sloping Land Using Rare Earth Elements As Tracers

Rare earth elements (REE) were used to study the temporal and spatial processes of soil erosion from different depths and sections of a slope. Two simulated rainfall events were applied to a prepared plot with a slope of 22°. The total runoff and sediment yield were collected every minute during the rainfall events. During the first twenty minutes of the first rainfall event, the average rate of rill erosion and the accumulated sediment yield due to rill erosion was 0.5 and 0.3 times higher than for sheet erosion. During this time, most of the erosion occurred on the lower one third of the plot. After 20 min, rill erosion became the dominant process on the slope. The average acceleration in the rate of rill erosion, the rate of rill erosion and the accumulated sediment yield due to rill erosion were 42, 6 and 4 times higher than that of sheet erosion, respectively. During the first 35 minutes of the second rainfall event, the average acceleration in the rate of rill erosion was 6～9 times higher than that of sheet erosion. Afterwards, the slope became nearly stable with little change in either rill or sheet erosion rates. Initially, most of the rill erosion occurred in the lower third of the slope but later the preexisting rillhead in the middle section of the slope became reactivated and erosion in this section of the slope increased rapidly. These results indicate that REE tracer technology is a valuable tool for quantifying spatial and temporal changes in erosion from a soil slope.

Payment for Environmental Services:The Sloping Land Conversion Program in Ningxia Autonomous Region of China

China＇s Sloping Land Conversion Program has been implemented since 2002. It aims to achieve goals of ecological recovery and poverty alleviation, by retiring steeply sloping land from crop production and freeing surplus agricultural labor for off-farm activities. Given the huge investment that has been poured into it, and its ecological and social impacts, this government-initiated program has attracted significant academic attention and triggered a flood of debate. Since 2004, the debate has concentrated on the sustainability of the program. Although targets have been overachieved in some provinces, concern has still emerged regarding the livelihood of farmers after subsidies stop. The present paper analyzes the implementation of the Sloping Land Conversion Program in Ningxia Autonomous Region, with a focus on the required social capital for sustained participation o f farmers and the development of off-farm economic activities.

Estimating water distribution of the rotating sprinkler with pulsating pressure on sloping land

Pulsating pressure plays an important role in improving the poor irrigation quality and the uneven water distribution caused by the terrain slope.Water distribution is one of the key factors in design of the sprinkler irrigation system,however,it is difficult to measure in practice.To provide appropriate technical parameters for the design of sprinkler irrigation system with pulsating pressure on sloping land,a mathematical model was established according to the water conservation principle and finite element idea,and its accuracy was experimentally verified.The model was applied to study the effects of terrain slope,sprinkler arrangement,sprinkler spacing and average pulsating pressure on water distribution on sloping land.The results showed that the water distribution was more favorable under the gentle terrain slope,when slope decreased from 25%to 5%,the uniformity increased from 74.47%to 86.22%.Sprinklers arranged in equilateral triangle and with the spacing close to R_(0)had the best water distribution uniformity,the uniformity coefficient(CU)of which was 11.43%and 8.75%higher than that in square and rectangular arrangement,respectively.The CU increased with the increase of the average pulsating pressure.However,the effect of increasing water pressure on promoting the uniformity of water distribution gradually decreases.Therefore,when using the Rainbird R5000 sprinkler on sloping land with pulsating pressure,it is suggested that the sprinkler irrigation systems should be arranged below the terrain slope of 20%,and operated at the average pulsating pressure of 300 kPa.The suitable sprinkler arrangement is the equilateral triangle,and with the spacing of 0.8R_(0)to 1.0R_(0).

Effectiveness of sloping agricultural land technology on soil fertility status of mid-hills in Nepal

Hedgerows with intercropping systems were established at the ICIMOD test and demonstration site at Godawari to assess the effective- ness of Sloping Agricultural Land Technology （SALT） in reducing run- off water volume, controlling soil loss, increasing crop production, and improving soil fertility in the mid-hills of Nepal. Runoff water volume （1996-2002）, soil loss （1996-2002） and maize yield （1995-2001）, and soil fertility-related parameters were assessed on SALT models with three factors： the type of nitrogen-fixing plant, the farmers＇ practice, and fertilizer use. Results showed a significant effect of Alnus nepalensis and/or Indigofera dosua on runoff water volume, soil loss, crop produc- tion, soil water retention, and soil nutrients （NPK）. Farmers＇ practice and fertilization did not play a significant role in reducing runoff water and soil loss. However, farmers＇ practice significantly increased crop produc- tion. Therefore, integrating soil conservation approaches on SALT sys- tems enhances stable economic output to hills and mountain farmers.

Monitoring the Cultivated Slope Land in the Three Gorges Reservoir Area Based on Remote Sensing and GIS

By means of combining auto-extraction with manual interpretation, the current distribution information about cultivated land is obtained. The distribution information of 1992 is extracted from the dynamic polygons of 2002. The monitoring mini-system of the cultivated slope land is established. In the system, detailed surveys, focused on the resources of cultivated slope land, are carried out. The results indicate that the area of the cultivated slope land is very large. Meanwhile, there are lots of cultivated steep slopes with gradient above 35°. The areas of steep land cultivated had been slowly reduced from 1992 to 2002. At the same time, the pressures of returning farm land to forestry are great in all counties. The conflicts between population growth, insufficient grain supply and stagnant economic development sharpen increasingly. It is inevitable to improve the agricultural structure.

Water Availability for Winter Wheat Affected by Summer Fallow Tillage Practices in Slope Dryland

The tillage experiments for winter wheat were conducted on the slope farmland in Luoyang, Henan Province in the semihumid to arid loess plateau areas of North China. Different tillage methods including reduced tillage(RT), no-till(NT), 2 crops/year(2C), subsoiling(SS), and conventional tillage(CT)were compared to determine the effects of tillage methods on soil water conservation, water availability, and wheat yields in a search for better farming systems in the areas. The NT and SS showed good effects on water conservation. The soil water storage increased 12 - 33 mm with NT and 9-24 mm with SS at the end of summer fallow periods. The soil evaporation with NT and SS decreased 7-8 mm and 34 - 36 mm during the fallow periods of 1999 and 2001, respectively. Evapotranspiration(ET)with NT and SS increased about 47 mm during wheat growth periods of 2000 to 2001. Treatment RT and 2C had low water storage and high water losses during the fallow periods. The winter wheat yields with conservation tillage practices were improved in the 2nd year, increased by 3, 5 and 8% with RT, NT and SS, respectively, compared with CT. The highest wheat yields were obtained with subsoiling, and the maximum economic benefits from no-till. All conservation tillage practices provided great benefits to saving energy and labors, reducing operation inputs, and increasing economic returns. No-till and subsoiling have shown promise in increasing water storage, reducing water loss, enhancing water availability, and saving energy, as well as increasing wheat yield.

Methodology for the Calculation of the Runoff Coefficient with the Arrangement Tirado

For this research work, an adequate methodology was sought for the calculation of the runoff coefficient with the Tirado arrangement. To achieve this, first, the variables that affect the runoff coefficient were identified, then the model was described with the Tirado arrangement, and as a third part for the calculation of the runoff coefficient, the Tirado model is proposed. From the theory for the calculation of the runoff coefficient, the equation of the weighted coefficients and the expression of Nadal were manipulated, resulting in the following relationship , considering this as the expression for the arrangement Tirado. The expression is tested with different intensities, the magnitudes correspond to 150, 200, 250 and 300 mm/hrs, resulting in runoff coefficient 0.82, 0.87, 0.89, 0.91 respectively. This means that, the higher the intensity, the runoff coefficient will be higher, logically the characteristics of the basin affect that this coefficient has variation in the space studied.

Using REE Tracers to Measure Sheet Erosion Changing to Rill Erosion

Rare earth element(REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different REE on different soil depth across a slope in an indoor plot, two simulated rainfalls were applied to study the change of erosion type and the rill erosion process. The results indicate that the main erosion type is sheet erosion at the beginning of the rainfalls, and serious erosion happens after rill erosion appears. Accumulated sheet and rill erosion amount increases with the rainfalls time. The percentage of sheet erosion amount decreases and rill erosion percentage increases with time. At the end of the rainfalls, the total rill erosion amounts are 4.3 and 5 times more than sheet erosion. In this paper, a new REE tracer method was used to quantitatively distinguish sheet and rill erosion amount. The new REE tracer method should be useful to future studying of erosion processes on slope lands.