| Through the calculation of the water footprint of maize productionin in Changchun City from 1960 to 2012, the paper analyzes interannual variation of the water footprint of maize productionin and the variation of the strutures of green water footprint, blue water footprint and grey water footprint in Changchun City in recent 53 years, exploring the spatial distribution and influencing factors of the water footprint of maize production in Changchun City, puting forward some countermeasures to optimize the allocation of water and soil resources for maize production in Changchun City.The main research contents and conclusions are as follows:First, the structures of green water footprint, blue water footprint and grey water footprint of maize productionin are different and constantly changing in Changchun City from 1960 to 2012. Nearly 53 years, the average proportion of green water footprint, blue green water footprint and grey water footprint of maize productionin are 66%, 25% and 9%. The green water footprint and the blue water footprint show a downward trend while the proportion of grey water footprint is significantly increased.Second, the average maize production water footprint is 1.39 m3/kg in Changchun City from 1960 to 2012, obviously decreased, and the average annual decrease is 0.0472 m3/kg/a. The past 53 years, the average green water footprint is 0.91m3/kg, significantly reduced, and the decreasing trend is 0.0364m3/kg/a. Average blue water footprint for 0.35m3/kg is also decreased significantly and the reduced tendency is 0.015m3/kg/a. The grey water footprint for 0.13m3/kg on average is increased significantly, rising to 0.0042m3/kg/a.Third, the city of Changchun has six counties( cities, districts). Their spatial distribution of total water footprint of maize production changed markedly in 1995(flat water year), 1999(dry year) and 2006(wet year). Six counties(cities,districts) the total water footprint of maize production are in four grades in dry year while flat water is distributed in three levels and wet year is in two grades, that is, the more precipitation we have, the less ranks of maize production in the total water footprint distribute and the smaller the gaps exist among the six counties(cities and districts). And the more precipitation we have, the lower the levels distribute,which total water footprint is smaller.Fourth, water footprint of maize production is affected by meteorological factors and social factors.Winds in Meteorological factors is the bigges factors on water footprint of maize production. Influence of social production factors on the water footprint of maize production is larger than meteorological elements, especially fertilizer use and agricultural power.Because the increased use of fertilizers and agricultural machinery power have contributed greatly to the increase of maize yield in Changchun, indirectly reducing the water footprint of maize production. Agricultural machinery power increase shows that maize production towards large-scale, intensive development and it has a positive influence on reducing the water footprint of maize production.Meanwhile, the more fertilizer increases,the more the grey water footprint increases.Fifth, we use the scientific and reasonable irrigation of maize so that we can do "when do irrigation", "because of the need for irrigation" and put forward optimal solution for irrigation combining of soil-water curve. Full development and the use of modern technologies in agriculture can increase maize yields, thus we can reduce the water footprint of maize production, and effectively enhance the utilization efficiency of water resources in Changchun City. To improve the water resources management system, establish effective management measures, we must start from the improvement of agricultural ecological environment combining persist exploitation and utilization, protection, governance, so that we achieve unification of economic, ecological and social benefits. |
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