Nitrogen is one of the major plant nutrients without which the agricultural production is not possible. Nitrogen use in Indian agriculture was nearly 55000 tons in 1950-1951 that increased to 11.31 million tons in 200...Nitrogen is one of the major plant nutrients without which the agricultural production is not possible. Nitrogen use in Indian agriculture was nearly 55000 tons in 1950-1951 that increased to 11.31 million tons in 2001-2002. The total food production of the country has also experienced the similar increase from 50.83 to 222 million tons in the respective years. Interestingly the N fertilizer consumption of India remained almost constant during the last six years indicating the possibility of reducing N consumption. The highest N consumption is in North zone owing to the introduction of rice-wheat cropping system followed by West, South and East.The N use efficiency has been reported to be varying between 30% to 50% depending on the crops and the management. But in most of the cases, N use efficiency has been calculated based on the total N removed by the crops (above ground part only) ignoring the N content left in the roots. It has been observed in controlled experiments that the total N uptake by roots varied from 18% to 44% of the total N removed by the above ground parts, i.e. grain and straw. If the root N is also accounted, the N use efficiency will be higher than reported. The management of other organic sources has to be improved so as to increase the fertilizer use efficiency as well as to check the direct release of N in the atmosphere. In this review all these issues will be dealt.展开更多
Urban population growth is driving the expansion of urban and peri-urban agriculture(UPA)in developing countries.UPA is providing nutritious food to residents but the manures produced by UPA livestock farms and other ...Urban population growth is driving the expansion of urban and peri-urban agriculture(UPA)in developing countries.UPA is providing nutritious food to residents but the manures produced by UPA livestock farms and other wastes are not properly recycled.This paper explores the effects of four scenarios:(1)a reference scenario(business as usual),(2)increased urbanization,(3)UPA intensification,and(4)improved technology,on food-protein self-sufficiency,manure nitrogen(N)recycling and balances for four different zones in a small city(Jimma)in Ethiopia during the period 2015-2050.An N mass flow model with data from farm surveys,field experiments and literature was used.A field experiment was conducted and N use efficiency and N fertilizer replacement values differed among the five types of composts derived from urban livestock manures and kitchen wastes.The N use efficiency and N fertilizer replacement values were used in the N mass flow model.Livestock manures were the main organic wastes in urban areas,although only 20 to 40%of animal-sourced food consumed was produced in UPA,and only 14 to 19%of protein intake by residents was animal-based.Scenarios indicate that manure production in UPA will increase 3 to 10 times between 2015 and 2050,depending on urbanization and UPA intensification.Only 13 to 38%of manure N will be recycled in croplands.Farm-gate N balances of UPA livestock farms will increase to>1 t·ha−1 in 2050.Doubling livestock productivity and feed protein conversion to animal-sourced food will roughly halve manure N production.Costs of waste recycling were high and indicate the need for government incentives.Results of these senarios are wake-up calls for all stakeholders and indicate alternative pathways.展开更多
文摘Nitrogen is one of the major plant nutrients without which the agricultural production is not possible. Nitrogen use in Indian agriculture was nearly 55000 tons in 1950-1951 that increased to 11.31 million tons in 2001-2002. The total food production of the country has also experienced the similar increase from 50.83 to 222 million tons in the respective years. Interestingly the N fertilizer consumption of India remained almost constant during the last six years indicating the possibility of reducing N consumption. The highest N consumption is in North zone owing to the introduction of rice-wheat cropping system followed by West, South and East.The N use efficiency has been reported to be varying between 30% to 50% depending on the crops and the management. But in most of the cases, N use efficiency has been calculated based on the total N removed by the crops (above ground part only) ignoring the N content left in the roots. It has been observed in controlled experiments that the total N uptake by roots varied from 18% to 44% of the total N removed by the above ground parts, i.e. grain and straw. If the root N is also accounted, the N use efficiency will be higher than reported. The management of other organic sources has to be improved so as to increase the fertilizer use efficiency as well as to check the direct release of N in the atmosphere. In this review all these issues will be dealt.
基金part of the CASCAPE project funded by the Dutch Ministry of Foreign Affairs through the Embassy of the Kingdom of the Netherlands in Addis Ababa,Ethiopia(5120915001).
文摘Urban population growth is driving the expansion of urban and peri-urban agriculture(UPA)in developing countries.UPA is providing nutritious food to residents but the manures produced by UPA livestock farms and other wastes are not properly recycled.This paper explores the effects of four scenarios:(1)a reference scenario(business as usual),(2)increased urbanization,(3)UPA intensification,and(4)improved technology,on food-protein self-sufficiency,manure nitrogen(N)recycling and balances for four different zones in a small city(Jimma)in Ethiopia during the period 2015-2050.An N mass flow model with data from farm surveys,field experiments and literature was used.A field experiment was conducted and N use efficiency and N fertilizer replacement values differed among the five types of composts derived from urban livestock manures and kitchen wastes.The N use efficiency and N fertilizer replacement values were used in the N mass flow model.Livestock manures were the main organic wastes in urban areas,although only 20 to 40%of animal-sourced food consumed was produced in UPA,and only 14 to 19%of protein intake by residents was animal-based.Scenarios indicate that manure production in UPA will increase 3 to 10 times between 2015 and 2050,depending on urbanization and UPA intensification.Only 13 to 38%of manure N will be recycled in croplands.Farm-gate N balances of UPA livestock farms will increase to>1 t·ha−1 in 2050.Doubling livestock productivity and feed protein conversion to animal-sourced food will roughly halve manure N production.Costs of waste recycling were high and indicate the need for government incentives.Results of these senarios are wake-up calls for all stakeholders and indicate alternative pathways.
