Soil erosion and nutrient loss due to erosion are world-wide problems. Similar to soil loss by erosion, soil nitrogen (N) loss by erosion in small catchments is affected by vegetation coverage. The practice of compreh...Soil erosion and nutrient loss due to erosion are world-wide problems. Similar to soil loss by erosion, soil nitrogen (N) loss by erosion in small catchments is affected by vegetation coverage. The practice of comprehensive management for catchments mainly by adjusting cropland, grassland and woodland areas was widely adopted to reduce soil and water loss in catchments of the Chinese Loess Plateau. Three experiments under natural and artificial rainfall conditions on N loss by erosion for a model catchment and for an actual catchment in Zhifanggou of Ansai County in China was performed to determine the relationships between comprehensive management and N loss by runoff in small catchments. The results for vegetation coverage of 60%, 40%, 20% and 0 show that runoff loss of ammonium, nitrate, and total N were 87.08, 44.31, 25.16, 13.71 kg/km(2); 85.50, 74.06, 63.95, 56.23 kg/km(2); and 0.18, 1.18, 1.98, 7.51 t/ km(2), respectively. Due to reduction in the size of cropped area on steeply sloping land, soil N loss by erosion in the catchments was decreased by 15.8% as compared with that in 1992, i.e., from 8 758.5 kg in 1992 to 7 562.2 kg in 1998. Whereas, catchments act as a filter for ammonium and nitrate in rain, the catchment filtering effects on nitrate is remarkably higher than that on ammonium. The enrichment of < 20 mum aggregate in sediment results in the enrichment of organic matter and total N in flood sediment. Greater vegetation coverage can effectively decrease soil erosion and total N loss. However, soil mineral N loss increased as vegetation coverage increased.展开更多
Identifying land management practices(LMPs)that enhance on-site sediment management and crop productivity is crucial for the prevention,reduction,and restoration of land degradation and contributing to achieving land ...Identifying land management practices(LMPs)that enhance on-site sediment management and crop productivity is crucial for the prevention,reduction,and restoration of land degradation and contributing to achieving land degradation neutrality(LDN).We reviewed studies in Ethiopia to assess the effects of LMPs on soil loss(84 studies)and crop productivity(34 studies)relative to control practice.Yield variability on conserved lands was assessed using 12,796 fixed plot data.Effects of LMP on soil loss were 0.5-55 t ha^(−1)y^(−1)compared to control practices yielding 50 to 140 t ha^(−1)y^(−1).More than 55%of soil loss records revealed soil loss less than the tolerable rate(10 t ha^(−1)).Area closure,perennial vegetation cover,agronomic practices,mechanical erosion control practices,annual cropland cover,and drainage groups of practices led to 74.0±18.3%,69.0±24.6%,66.2±30.5%,66.1±18.0%,63.5±20.0%,and 40±11,1%soil loss reduction,respectively.A yield increase of 25.2±15.0%,37.5±28.0%,and 75.4±85.0%was found from drainage,agronomy,and mechanical erosion control practices,respectively.The average yield loss by erosion on fields without appropriate land management practice and on conserved fields was 26.5±26.0%and 25±3.7%,respectively.The findings suggest that practices that entail a continuous presence of soil cover during the rainy season,perennial vegetation,retention of moisture,and barriers for sediment transport were most effective at decreasing soil loss and increasing productivity.This review provides evidence to identify the best LMP practices for wider adoption and inform decision-making on LMP investments towards achieving sustainable solutions to reverse land degradation.展开更多
文摘Soil erosion and nutrient loss due to erosion are world-wide problems. Similar to soil loss by erosion, soil nitrogen (N) loss by erosion in small catchments is affected by vegetation coverage. The practice of comprehensive management for catchments mainly by adjusting cropland, grassland and woodland areas was widely adopted to reduce soil and water loss in catchments of the Chinese Loess Plateau. Three experiments under natural and artificial rainfall conditions on N loss by erosion for a model catchment and for an actual catchment in Zhifanggou of Ansai County in China was performed to determine the relationships between comprehensive management and N loss by runoff in small catchments. The results for vegetation coverage of 60%, 40%, 20% and 0 show that runoff loss of ammonium, nitrate, and total N were 87.08, 44.31, 25.16, 13.71 kg/km(2); 85.50, 74.06, 63.95, 56.23 kg/km(2); and 0.18, 1.18, 1.98, 7.51 t/ km(2), respectively. Due to reduction in the size of cropped area on steeply sloping land, soil N loss by erosion in the catchments was decreased by 15.8% as compared with that in 1992, i.e., from 8 758.5 kg in 1992 to 7 562.2 kg in 1998. Whereas, catchments act as a filter for ammonium and nitrate in rain, the catchment filtering effects on nitrate is remarkably higher than that on ammonium. The enrichment of < 20 mum aggregate in sediment results in the enrichment of organic matter and total N in flood sediment. Greater vegetation coverage can effectively decrease soil erosion and total N loss. However, soil mineral N loss increased as vegetation coverage increased.
文摘Identifying land management practices(LMPs)that enhance on-site sediment management and crop productivity is crucial for the prevention,reduction,and restoration of land degradation and contributing to achieving land degradation neutrality(LDN).We reviewed studies in Ethiopia to assess the effects of LMPs on soil loss(84 studies)and crop productivity(34 studies)relative to control practice.Yield variability on conserved lands was assessed using 12,796 fixed plot data.Effects of LMP on soil loss were 0.5-55 t ha^(−1)y^(−1)compared to control practices yielding 50 to 140 t ha^(−1)y^(−1).More than 55%of soil loss records revealed soil loss less than the tolerable rate(10 t ha^(−1)).Area closure,perennial vegetation cover,agronomic practices,mechanical erosion control practices,annual cropland cover,and drainage groups of practices led to 74.0±18.3%,69.0±24.6%,66.2±30.5%,66.1±18.0%,63.5±20.0%,and 40±11,1%soil loss reduction,respectively.A yield increase of 25.2±15.0%,37.5±28.0%,and 75.4±85.0%was found from drainage,agronomy,and mechanical erosion control practices,respectively.The average yield loss by erosion on fields without appropriate land management practice and on conserved fields was 26.5±26.0%and 25±3.7%,respectively.The findings suggest that practices that entail a continuous presence of soil cover during the rainy season,perennial vegetation,retention of moisture,and barriers for sediment transport were most effective at decreasing soil loss and increasing productivity.This review provides evidence to identify the best LMP practices for wider adoption and inform decision-making on LMP investments towards achieving sustainable solutions to reverse land degradation.
