Abstract
The estimated, effective increase of agricultural fertilizer applied in China by 10.57 Mts from 2006 to 2016 is a crucial factor affecting the water environment. Based on analyzing the nitrate-leaching rate, the nitrogen-fertilizer application rate, and crop yield in wheat and maize key cultivation divisions in China, this paper applied the grey water footprint analytical method to estimate THE grey water footprint and its proportion to total water footprint and analyzed the spatial differences from 2012 to 2016. Results showed that the grey water footprint of wheat was higher in North and Northwest China with an increasing trend, while that of maize was higher in Southwest and Northwest China because of high nitrogen application rates and low yields in these regions. Except for the Southwestern division, wheat’s grey water footprint was about 1.3 times higher than the blue water footprint, while, for maize, it was two to three times higher. When analyzing and planning water demand for crop irrigation, the water required for nonpoint source pollution due to chemical fertilizers should be considered. Focusing blue water (irrigation) alone, while neglecting green water and ignoring grey water footprints, it might lead to overestimation of available agricultural water resources and failure to meet the goals of sustainable use of water resources.
Highlights
The “1st National Census on Pollution Sources Bulletin” by the China Ministry of EnvironmentProtection [1], showed that, in China, agricultural production-related emissions of major pollutants, such as chemical oxygen demand, total nitrogen, and total phosphorus, have exceeded industrial and human activity pollution levels.The oxygen, nitrogen, and phosphorus pollutants have become the main source of pollution in the country, which accounts for 43.7%, 57.2%, and 67.4% of the total emissions, respectively
It is fundamental to study the spatial distribution of agricultural nonpoint source (NPS) pollution generation and emission, and objectively analyze the effect of agricultural production on aquatic environments to generate prevention strategies for the non-point source pollution and to control and reduce agricultural pollution
It was found that the main factors that contributed to a high WFgrey for wheat in North China were the high leaching nitrogen application rates
Summary
The “1st National Census on Pollution Sources Bulletin” by the China Ministry of EnvironmentProtection [1], showed that, in China, agricultural production-related (including cultivation, livestock, and poultry farming and aquaculture) emissions of major pollutants, such as chemical oxygen demand, total nitrogen, and total phosphorus, have exceeded industrial and human activity pollution levels.The oxygen, nitrogen, and phosphorus pollutants have become the main source of pollution in the country, which accounts for 43.7%, 57.2%, and 67.4% of the total emissions, respectively. Simona-Andreea et al [7] calculated the WFgrey for eight major crops in the Prut-Barlad catchment from 2005 to 2008 Their results showed that wheat had the highest WFgrey (58 Mm3 /year), which is followed by vegetables (52 Mm3 /year). Mekonnen et al [8] summarized the agricultural, industrial, and domestic activity WFgrey, and water pollution related to nitrogen loads, to fresh water in the basin area of different countries from 2002 to 2010. Results showed that China had the highest nitrogen emissions, which accounts for about 45% of the global grand total and results in the following WFgrey ranking: agriculture > domestic activity > industry. Domestic WFgrey studies focused on the calculation and evaluation of agricultural WFgrey caused by pollution of chemical fertilizers and pesticides at regional scales [9,10]. Zhang et al [9] used fixed leaching rates to calculate the WFgrey of the winter wheat-summer maize rotation, caused by the nitrogen fertilizer application in the North
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