It is not understood well that how the effects of land use and fish farming on the contents of alkali metals (Ca<sup>2+</sup>, Mg<sup>2+</sup>, K<sup>+</sup> and Na<sup>+</...It is not understood well that how the effects of land use and fish farming on the contents of alkali metals (Ca<sup>2+</sup>, Mg<sup>2+</sup>, K<sup>+</sup> and Na<sup>+</sup>) in small water bodies of pond and reservoir ecosystems at the watershed scale. In this study, the concentrations of Ca<sup>2+</sup>, Mg<sup>2+</sup>, K<sup>+</sup> and Na<sup>+</sup> in water bodies were measured for 103 ponds and reservoirs used as fish farming or surrounded by different agricultural land use types in the subtropical hilly watershed of Jinjing (105 km<sup>2</sup>), China. The two important environmental factors of fishing farming and agricultural land use influenced the spatial variation the contents of alkali metals. The ponds and reservoirs in residential area had significantly higher concentrations of Ca<sup>2+</sup> and Na<sup>+</sup> than those with other land use types, reflecting the influence of domestic wastewater. Compared with those of natural ponds with non-fish farming, no significant increase of alkali metal contents occurred in fish farming ponds, due to the regular cleaning of ponds by farmers. However, the effect of fish culture on alkali metal contents was still supported indirectly by the fact that the alkali metal contents significantly correlated with nitrate contents in fish farming ponds and but high related with that of DIP in natural ponds. The suitability assessment for irrigation on the pond water indicated that almost all of ponds were suitable for irrigation except some ponds surrounded by residential area and tea plantation. Generally, our results demonstrated that fish farming and agricultural land use affected the contents of alkali metals in ponds and reservoirs. The agricultural water irrigation would be with caution from the ponds with tea plantation and residential area in the subtropical hilly watershed.展开更多
Small scale farmers constitute about half of world＇s hungry people and include three quarters of Africa＇s malnourished children. The appropriate identification and characterization of this population and the constra...Small scale farmers constitute about half of world＇s hungry people and include three quarters of Africa＇s malnourished children. The appropriate identification and characterization of this population and the constraints it faces are essential for the design and the successful implementation of safety nets and to properly target their needs and effectively include them in agricultural development strategies. This paper aims at exploring the characteristics, limitations, and potential for agricultural development of small scale farmers in developing countries. It calculates four land cultivated thresholds which are then used as a measure to classify households that were surveyed in four developing countries. It empirically estimates the magnitudes of the smallholders, their characteristics, as well as their poverty status using the four thresholds. This analysis provides empirical evidence that small scale farmers still prevail in terms of population distribution in rural area settings in developing countries. Small scale farmers heavily rely on farm income as their form of livelihood and heavily contribute to the rural income. It also finds that land is unequally distributed among small and large scale farmers in the rural households. Small scale farmers also have the highest poverty rates in these rural settings.展开更多
文摘It is not understood well that how the effects of land use and fish farming on the contents of alkali metals (Ca<sup>2+</sup>, Mg<sup>2+</sup>, K<sup>+</sup> and Na<sup>+</sup>) in small water bodies of pond and reservoir ecosystems at the watershed scale. In this study, the concentrations of Ca<sup>2+</sup>, Mg<sup>2+</sup>, K<sup>+</sup> and Na<sup>+</sup> in water bodies were measured for 103 ponds and reservoirs used as fish farming or surrounded by different agricultural land use types in the subtropical hilly watershed of Jinjing (105 km<sup>2</sup>), China. The two important environmental factors of fishing farming and agricultural land use influenced the spatial variation the contents of alkali metals. The ponds and reservoirs in residential area had significantly higher concentrations of Ca<sup>2+</sup> and Na<sup>+</sup> than those with other land use types, reflecting the influence of domestic wastewater. Compared with those of natural ponds with non-fish farming, no significant increase of alkali metal contents occurred in fish farming ponds, due to the regular cleaning of ponds by farmers. However, the effect of fish culture on alkali metal contents was still supported indirectly by the fact that the alkali metal contents significantly correlated with nitrate contents in fish farming ponds and but high related with that of DIP in natural ponds. The suitability assessment for irrigation on the pond water indicated that almost all of ponds were suitable for irrigation except some ponds surrounded by residential area and tea plantation. Generally, our results demonstrated that fish farming and agricultural land use affected the contents of alkali metals in ponds and reservoirs. The agricultural water irrigation would be with caution from the ponds with tea plantation and residential area in the subtropical hilly watershed.
文摘Small scale farmers constitute about half of world＇s hungry people and include three quarters of Africa＇s malnourished children. The appropriate identification and characterization of this population and the constraints it faces are essential for the design and the successful implementation of safety nets and to properly target their needs and effectively include them in agricultural development strategies. This paper aims at exploring the characteristics, limitations, and potential for agricultural development of small scale farmers in developing countries. It calculates four land cultivated thresholds which are then used as a measure to classify households that were surveyed in four developing countries. It empirically estimates the magnitudes of the smallholders, their characteristics, as well as their poverty status using the four thresholds. This analysis provides empirical evidence that small scale farmers still prevail in terms of population distribution in rural area settings in developing countries. Small scale farmers heavily rely on farm income as their form of livelihood and heavily contribute to the rural income. It also finds that land is unequally distributed among small and large scale farmers in the rural households. Small scale farmers also have the highest poverty rates in these rural settings.
