Tillage and crop management effects on soil erosion in central Croatia

Soil erosion continues to be a primary cause for soil degradation and the loss of soil quality throughout the world. Our objectives were to quantify soil erosion (referred to as erosional drift) and to assign erosion risk to six tillage and crop management treatments evaluated from 1995 to 1999 for a 5-year maize (Zea mays L.), soybean (Glycine hyspida L.), winter wheat (Triticum aestivum L.), oil-seed rape (Brassica napus var. oleifera L.), and spring barley (Hordeum vulgare L.) plus double-crop soybean rotation on Stagnic Luvisols in central Croatia. Standard black fallow (tilled, unsown, and without any vegetative cover) Universal Soil Loss Equation (USLE) plots were used to establish the erosion potential associated with the rainfall pattern for each year. Soil loss from the check plots was several times greater than the T value, which is estimated to be 10 t ha⁻¹ per year. During the 2 years when spring seeded maize or soybean were grown (1995 and 1996) erosion risk was extremely high, especially for treatments where tillage and planting (row direction) were up and down the slope. When autumn seeded winter wheat or oil-seed rape were grown (1996/1997 or 1997/1998), soil erosion was insignificant. Also, except when plowing and sowing were up and down slope, erosion loss for the spring barley plus double-crop soybean crops in 1999 was insignificant. With no-tillage, soil erosion from the maize and soybean crops was reduced 40 and 65% compared to plowing up and down slope, even though the planting direction was still up and down the slope. With the exception of maize in 1995, erosion losses were moderate to insignificant when plowing and planting were performed across the slope. We conclude that erosion risk can be used as a reliable indicator of sustainable land management and that using no-tillage or plowing and planting perpendicular to the predominant slope are effective soil conservation practices for this region.     

接坝山地土壤水蚀、风蚀预报模型及强度分级研究——以丰宁满族自治县小坝子乡为例

以丰宁满族自治县小坝子乡为研究对象,在全面调查,获取资料,建立土地利用现状属性数据库的基础上,运用通用土壤流失方程USLE和打分评价相对模型分别建立了小坝子乡土壤水蚀、风蚀预报模型;并通过建立分级指标体系,对小坝子乡土壤侵蚀强度进行了分级研究。旨在探求接坝山地土壤侵蚀的特点和侵蚀程度,为该区域水土保持和防沙治沙提供科学依据     

SOTER支持下海南岛土壤侵蚀模拟与影响因子分析

基于SOTER数据库,利用USLE方程对海南岛土壤的现实和潜在侵蚀量进行了定量估算,结果表明海南岛92.82%的面积土壤侵蚀量在500t/km2·a以下,侵蚀主要发生在中坡度坡地和高坡度丘陵区;而由于其所处的特殊气候区,潜在侵蚀量巨大,中度以上侵蚀面积达到全岛的90.67%。酸性常湿雏形土、铝质湿润雏形土和铁质湿润雏形土相对侵蚀程度大,粉砂岩、泥岩地区最容易发生侵蚀。     

Large‐scale Modeling of Soil Erosion with RUSLE for Conservationist Planning of Degraded Cultivated Brazilian Pastures

Pasture degradation is one of the major environmental and economic problems of Brazilian livestock production. Based on the estimates of soil loss in 140,297 km² pasturelands of Goiás State and the Federal District, the effects of land use and management and conservation practices on soil erosion by water were evaluated. Soil loss was estimated with the empirical revised universal soil loss equation model under four scenarios of land use and management of pastures and the implementation of terraces. The effects of converting hilly areas into permanently preserved areas were also evaluated. Well‐managed pastures planted in terraces and highly sloped areas with native vegetation featured a reduction of 709% in the rate of soil erosion by water in comparison with poorly managed pastures without soil conservation practices. The environmental consequences of pasture degradation become particularly important when they are associated with land use in the Amazon and Cerrado biomes because farmers in these regions are forced to open new natural areas. In addition, the high indices of bare soil in degraded pastures contribute significantly to sediment deposition in rivers and dams. The modeling of soil loss is demonstrated to be an important tool for land use planning and supporting public policies focused on the sustainable use of natural resources. The results of these simulations demonstrate the importance of actions to recover degraded pastures, such as the Federal Government's program known as ABC (Low Carbon Agriculture). Copyright © 2015 John Wiley & Sons, Ltd.     

Conservation farming practices for small reservoir watersheds: a case study from Sri Lanka

Traditional agricultural villages in the dry zone of Sri Lanka are minor watersheds where small earth bank reservoirs provide water for irrigation and domestic purposes. The farmers practise rainfed farming on a shifting basis called chena in the reservoir catchments, which are being degraded due to soil erosion. The consequent sedimentation in reservoirs has reduced the extent of irrigation, and the total farming system has lost its ecological balance and economic sustenance. The present study aimed at identifying suitable farming methods for reservoir catchments in order to prevent further deterioration.The investigation was carried out on plot basis to assess soil loss and runoff from forest, scrub and cultivated lands as well as from four other types of farming lands namely plough-farming, bund-farming and two conservation farming practices: strip mulch and graded hedgerow farming. In graded hedgerow farming hedgerow trees are planted across the slope with a mild gradient of 0.4–0.5%. The study was carried out in a reservoir watershed at Maha Illuppallama, Sri Lanka during 1989/90 major rainy season.Results indicated that the two conservation farming practices generate 33–34% annual runoff while replenishing soil moisture of the watershed. Soil loss data showed that the conservation farming practices provide more than 80% protection against soil erosion while bunding can provide only 40% protection compared to existing shifting cultivation practices.     

基于GIS和USLE的宁乡市土壤侵蚀定量评价

以遥感影像数据、DEM数据、降雨数据、土壤类型数据为基础,通过GIS和RS技术,结合美国通用水土流失方程(USLE)估算宁乡市的土壤侵蚀模数,模型指标包括降雨侵蚀力因子(R)、土壤可侵蚀性因子(K)、坡度坡长因子(LS)、植被覆盖度因子(C)、水土保持措施因子(P)。评价结果表明,2015年宁乡市土壤平均侵蚀模数为1 410.64t/(km2·年),属于中度侵蚀等级状情况,土壤侵蚀类型主要为微度侵蚀、剧烈侵蚀和轻度侵蚀,侵蚀面积分别为1 548.87、434.16和397.91km2,占侵蚀总面积的53.84%、15.09%和13.88%。土壤侵蚀模数较高的地区主要集中在宁乡市的沩山、长冲等山地、丘陵地区。系统分析出宁乡市土壤侵蚀与USLE模型的相关影响因子的关系,海拔高程与土壤侵蚀强度成正相关关系,与侵蚀面积成负相关关系,在200m海拔高程地区微度侵蚀面积范围最大。县内土壤侵蚀面积最大地区是在25°以下的坡度带,土壤侵蚀面积总体随着坡度的增加而减小。土地利用类型中耕地和林地的土壤侵蚀最为严重,其次是城镇用地草地水域裸地。根据宁乡市土壤侵蚀现状,提出综合治理措施,以期为政府开展水土保持工作提供科学依据。     

牡丹江市退耕还林对区域土壤侵蚀的影响研究

将GIS与通用水土流失方程（USLE）相结合进行牡丹江市退耕还林前后土壤侵蚀状况分析,评价退耕还林对区域水土流失的影响。研究结果表明:轻度侵蚀面积由退耕前的1 600.12km²减小到退耕后的1 296.41km²,主要分布在西南部宁安地区;剧烈侵蚀由退耕前的3 161.52km²减少到退耕后的672.38km²,主要被极强度侵蚀代替,且集中分布在海拔较高的穆棱北部及林口南部、低山丘陵地带25°以下的旱田及林地上。总体而言,退耕还林工程缓解了区域严峻的水土流失态势,但仍需采取相关配套措施以期彻底改善区域水土流失状况,包括修筑梯田、水平等高耕作及深耕翻作业等,但根本措施在于发展区域经济,调整农业生产结构,保护退耕还林成果,从而实现区域生态经济协调发展。     

基于RS与GIS的龙口市土壤侵蚀评价研究

将研究区分成100 m×100 m的网格,以通用土壤侵蚀方程USLE为模型,利用RS与GIS技术获取土壤侵蚀的各影响因子,计算出每个单元格的年均侵蚀量和侵蚀模数,最终获得龙口市的土壤侵蚀总量和侵蚀强度分级.结果表明,龙口市年均侵蚀模数为982.5 t/(hm2·a),侵蚀强度属轻度;占龙口市总面积63.6%的区域为微度侵蚀,微度侵蚀对总侵蚀量的贡献率为8.1%;而强度以上侵蚀虽然只占土地总面积的4.7%,侵蚀量却占到总侵蚀量的40.6%.     

基于Logistic回归和RBF神经网络的土壤侵蚀模数预测

[目的]寻求估算土壤侵蚀模数的新方法,并通过GIS实现对土壤侵蚀空间分布情况的预测。[方法]采用土壤侵蚀模数作为判别条件,分别验证基于Logistic回归和RBF神经网络而建立的土壤侵蚀预报模型的适用性,进而构建并验证改进模型——LOG-RBF神经网络土壤侵蚀预测模型。[结果](1)Logistic回归模型判别目标土地是否发生土壤侵蚀的优势明显,未发生和发生土壤侵蚀的预测正确率分别为77.4%和97.9%,总预测正确率为94.9%。(2)RBF神经网络模型估计土壤侵蚀模数的能力较强,模拟结果的相对误差和平方和误差分别为0.612%和13.292,R2为0.57。(3)LOG-RBF神经网络土壤侵蚀预测模型预测结果的相对误差和平方和误差比RBF神经网络模型模拟结果分别降低了0.157%和2.601。R2为0.82,拟合程度上优于RBF神经网络模型。随着土壤侵蚀模数的增大,错估现象呈逐渐减少趋势。通过受试者工作特征曲线的判别,LOG-RBF神经网络模型的曲线下面积值比RBF神经网络模型大0.063,模型判断的准确性更高。[结论]利用LOG-RBF神经网络土壤侵蚀预测模型可更准确地估计土壤侵蚀模数,基于GIS能够预测土壤侵蚀的空间分布情况。     

Application of Universal Soil Loss Equation (USLE) to mountainous forests in Japan

Universal Soil Loss Equation (USLE), originally developed by the USDA for agricultural lands and then used throughout the world, was applied in mountainous forest terrain in Japan. The slope length and steepness factors were extended for long slope lengths and steep slopes by recalculating the data from available literature in Japan and by using data from supplementary erosion experiments. As such, we conclude that the USLE can be used successfully to estimate surface erosion on long, steep mountainous forest slopes. The cover and management factors of many kinds of natural and artificial forest stands, cutting types, and disturbance regimes were calculated from the literature. The support practice factors of many types of soil and water conservation practices were also calculated from published information. Based on these results, we showed that the USLE can be applied to estimations of soil erosion from wide areas including many kinds of agricultural and forest lands. This study was funded by the Agricultural, Forestry, and Fishery Technology Council Office for comprehensive studies on agriculture, forestry, and fisheries and the agricultural, forestry, and fishery trading, resources, and environments.