The soil nutrient losses due to excessive soil loss on Loess Plateau were studied by means of runoff plotsand systematical determination of soil nutrients both in sediments and runoff.The results show that theamounts ...The soil nutrient losses due to excessive soil loss on Loess Plateau were studied by means of runoff plotsand systematical determination of soil nutrients both in sediments and runoff.The results show that theamounts of nutrient losses depended on the amounts of erosion sediments. Along with sediment, 11-197 kgnitrogen/hectare and 9-174 kg phosphorus/hectare were lost, accounting for 92.46-99.47 percent of the totalamount of nitrogen loss and 99.85-99.99 percent of the total amount of phosphorns loss respectively. Thenutrient losses, very small in runoff, were mainly attributed to erosion of a few rainstorms during a year. Thenutrient level in sediment was mostly higher than that in the original soil. Planting grass evidently reducedthe losses of soil nutrients. The N level was lower in runoff than in rainfall so that the N loss from runoffconld be made up by rainfall. Fertilizer application to crops raised the nutrient level in runoff.展开更多
In order to measure dust's nutrient input on farmland in different agro-ecological zones, Harmattan dust was sampled by mats with plastic straw in Ghana between 2002–2006. The inputs of total nutrients by Harmatt...In order to measure dust's nutrient input on farmland in different agro-ecological zones, Harmattan dust was sampled by mats with plastic straw in Ghana between 2002–2006. The inputs of total nutrients by Harmattan dust in Ghana per Harmattan period were about 1–2 kg Ca ha-1, 0.5–2 kg K ha-1, 0.5–1.5 kg Mg ha-1and less than 0.5 kg P ha-1. Compared with the annual input of nutrients by precipitation, the dust accounted for 10% or less of Ca, Mg and K but approximately 20%–40% of P. The input of nutrients by dust was only valid for areas with vegetation, because in areas with none or sparse vegetation, loss of soil due to wind erosion and hereby loss of nutrients might be significant. In farmland areas with bare and vegetated fields there seemed to be an internal redistribution of the nutrients and not a net gain of nutrients from outside the area(long-range transported dust). The input of P by dust might be of some importance in the traditional shifting cultivation systems, while the inputs of other three nutrients of Ca, Mg and K were so low that they must be considered insignificant. In the intensive agriculture systems with huge inputs of manures and fertilizers the nutrient input by dust is insignificant and could be neglected.展开更多
文摘The soil nutrient losses due to excessive soil loss on Loess Plateau were studied by means of runoff plotsand systematical determination of soil nutrients both in sediments and runoff.The results show that theamounts of nutrient losses depended on the amounts of erosion sediments. Along with sediment, 11-197 kgnitrogen/hectare and 9-174 kg phosphorus/hectare were lost, accounting for 92.46-99.47 percent of the totalamount of nitrogen loss and 99.85-99.99 percent of the total amount of phosphorns loss respectively. Thenutrient losses, very small in runoff, were mainly attributed to erosion of a few rainstorms during a year. Thenutrient level in sediment was mostly higher than that in the original soil. Planting grass evidently reducedthe losses of soil nutrients. The N level was lower in runoff than in rainfall so that the N loss from runoffconld be made up by rainfall. Fertilizer application to crops raised the nutrient level in runoff.
基金supported by the Danida-Enreca project "Ecological Laboratory" of the University of Ghana, Legon, Accra, Ghana
文摘In order to measure dust's nutrient input on farmland in different agro-ecological zones, Harmattan dust was sampled by mats with plastic straw in Ghana between 2002–2006. The inputs of total nutrients by Harmattan dust in Ghana per Harmattan period were about 1–2 kg Ca ha-1, 0.5–2 kg K ha-1, 0.5–1.5 kg Mg ha-1and less than 0.5 kg P ha-1. Compared with the annual input of nutrients by precipitation, the dust accounted for 10% or less of Ca, Mg and K but approximately 20%–40% of P. The input of nutrients by dust was only valid for areas with vegetation, because in areas with none or sparse vegetation, loss of soil due to wind erosion and hereby loss of nutrients might be significant. In farmland areas with bare and vegetated fields there seemed to be an internal redistribution of the nutrients and not a net gain of nutrients from outside the area(long-range transported dust). The input of P by dust might be of some importance in the traditional shifting cultivation systems, while the inputs of other three nutrients of Ca, Mg and K were so low that they must be considered insignificant. In the intensive agriculture systems with huge inputs of manures and fertilizers the nutrient input by dust is insignificant and could be neglected.
