4.3. Implications for agricultural diffuse pollution control The results demonstrate the significance of simplified quantitative N loading indicators for diffuse pollution assessment in a typical basin. The main pollution source is farmland in the agricultural basin, which is mainly converted from natural land cover. The lower metal variable values in the paddy rice area indicate that the aquatic condition accelerates transport. Diffuse N loading in upland sub-basins is, on average, approximately 50% less than that in rice paddies. Strategies for reducing diffuse N yield from farmland should focus on less N input and more convenient transport pathways within the basin. The spatial and vertical variations in soil TN and metal contents can be useful in planning fertilizer application, and some preliminary reports of Fig. 7. Weight plot of the first and second PLSR components for the upland (left) and paddy rice (right) sub-basins. 38 H. Huang et al. / Soil & Tillage Research 144 (2014) 32–40fertilizer balance exist for European countries (Webb et al., 2000). Based on the data from the 1.5-km sampling grid, appropriate fertilizer use will prevent diffuse N loading from the source. Due to the built spatial relationship, the diffuse N loading can be predicted as a function of the soil properties. This may be a good method for assessing pollution yield in agricultural basins when more soil data are available. The considered basin includes concentrated forest and wetland areas up and down stream, which can affect the diffuse N pollution transport pathway (Braskerud, 2002).
4.3. Implications for agricultural diffuse pollution control The results demonstrate the significance of simplified quantitative N loading indicators for diffuse pollution assessment in a typical basin. The main pollution source is farmland in the agricultural basin, which is mainly converted from natural land cover. The lower metal variable values in the paddy rice area indicate that the aquatic condition accelerates transport. Diffuse N loading in upland sub-basins is, on average, approximately 50% less than that in rice paddies. Strategies for reducing diffuse N yield from farmland should focus on less N input and more convenient transport pathways within the basin. The spatial and vertical variations in soil TN and metal contents can be useful in planning fertilizer application, and some preliminary reports of Fig. 7. Weight plot of the first and second PLSR components for the upland (left) and paddy rice (right) sub-basins. 38 H. Huang et al. / Soil & Tillage Research 144 (2014) 32–40fertilizer balance exist for European countries (Webb et al., 2000). Based on the data from the 1.5-km sampling grid, appropriate fertilizer use will prevent diffuse N loading from the source. Due to the built spatial relationship, the diffuse N loading can be predicted as a function of the soil properties. This may be a good method for assessing pollution yield in agricultural basins when more soil data are available. The considered basin includes concentrated forest and wetland areas up and down stream, which can affect the diffuse N pollution transport pathway (Braskerud, 2002).
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