The rainfed region in Iraq comprises an area of more than 5 million ha of forest,grazing and farmland areas.Except the plains,the region suffers from moderate to severe water erosion due mainly to overgrazing and land...The rainfed region in Iraq comprises an area of more than 5 million ha of forest,grazing and farmland areas.Except the plains,the region suffers from moderate to severe water erosion due mainly to overgrazing and land mismanagement.Due to population growth and the shortage in water resources,an expansion in land used for agriculture in the region is expected.Terracing is an option when utilizing sloping land for agricultural production.A terrace design criterion was developed for the region in which terrace spacing was determined using the Revised Universal Soil Loss Equation(RUSLE);terrace channel specifications were determined using conventional hydraulic computations.Analyses showed that terracing is feasible on rolling and hilly sloping land in the high rainfall zone(seasonal rainfall 4600 mm)where economic crops are grown to offset the high cost of terrace construction and maintenance.In the medium and low rainfall zones(seasonal rainfall 400–600 mm and 300–400 mm),terracing for water erosion control is generally not needed on cultivated land less than 10%in slope where wheat and barley crops are normally grown;however,pioneer research projects are needed to assess the feasibility of terraces of the level(detention)type to conserve rain water in these two zones for a more successful rainfed farming venture.展开更多
USLE/RUSLE是土壤侵蚀监测与预报的核心工具,方程中各因子赋值的合理性决定了方程应用结果的准确度。然而,由于我国地形条件的复杂性等原因,方程在我国范围内的应用受到限制。因此,为明晰土壤流失方程各因子计算中需把握的关键因素,以...USLE/RUSLE是土壤侵蚀监测与预报的核心工具,方程中各因子赋值的合理性决定了方程应用结果的准确度。然而,由于我国地形条件的复杂性等原因,方程在我国范围内的应用受到限制。因此,为明晰土壤流失方程各因子计算中需把握的关键因素,以及当前我国研究中存在的主要问题,采用文献综合对比研究的方法,通过CNKI中国学术期刊全文数据库和Web of Science数据库,搜集了土壤流失方程因子相关文献共373篇。文献综合分析结果表明:各因子的研究普遍存在缺乏估算公式选用和估算结果的精度检验,坡长坡度因子存在公式误用的情况,作物覆盖与管理因子、水土保持措施因子缺少系统性定量计算的方法,土壤可蚀性因子计算的背景条件差异大,难以进行横向比较。为此,提出两条提高模型使用精度的建议,一是通过建设标准化的地面监测系统,系统观测和建立土壤侵蚀因子定量方法,二是明确此类模型应用边界,在较为适合的环境应用。展开更多
文摘The rainfed region in Iraq comprises an area of more than 5 million ha of forest,grazing and farmland areas.Except the plains,the region suffers from moderate to severe water erosion due mainly to overgrazing and land mismanagement.Due to population growth and the shortage in water resources,an expansion in land used for agriculture in the region is expected.Terracing is an option when utilizing sloping land for agricultural production.A terrace design criterion was developed for the region in which terrace spacing was determined using the Revised Universal Soil Loss Equation(RUSLE);terrace channel specifications were determined using conventional hydraulic computations.Analyses showed that terracing is feasible on rolling and hilly sloping land in the high rainfall zone(seasonal rainfall 4600 mm)where economic crops are grown to offset the high cost of terrace construction and maintenance.In the medium and low rainfall zones(seasonal rainfall 400–600 mm and 300–400 mm),terracing for water erosion control is generally not needed on cultivated land less than 10%in slope where wheat and barley crops are normally grown;however,pioneer research projects are needed to assess the feasibility of terraces of the level(detention)type to conserve rain water in these two zones for a more successful rainfed farming venture.
文摘USLE/RUSLE是土壤侵蚀监测与预报的核心工具,方程中各因子赋值的合理性决定了方程应用结果的准确度。然而,由于我国地形条件的复杂性等原因,方程在我国范围内的应用受到限制。因此,为明晰土壤流失方程各因子计算中需把握的关键因素,以及当前我国研究中存在的主要问题,采用文献综合对比研究的方法,通过CNKI中国学术期刊全文数据库和Web of Science数据库,搜集了土壤流失方程因子相关文献共373篇。文献综合分析结果表明:各因子的研究普遍存在缺乏估算公式选用和估算结果的精度检验,坡长坡度因子存在公式误用的情况,作物覆盖与管理因子、水土保持措施因子缺少系统性定量计算的方法,土壤可蚀性因子计算的背景条件差异大,难以进行横向比较。为此,提出两条提高模型使用精度的建议,一是通过建设标准化的地面监测系统,系统观测和建立土壤侵蚀因子定量方法,二是明确此类模型应用边界,在较为适合的环境应用。
