华北平原冬小麦-夏玉米生产灰水足迹及其县域尺度变化特征

Abstract

Much of the North China Plain( NCP) is dedicated to cultivation of winter wheat and summer maize. In order to achieve high crop yields,nitrogen fertilizer has been used in excess,constituting the major cause of water pollution in the area. The saying thatall rivers are dry and pollutedhas come to characterize the NCP's water resource environment. The grey water footprint of a product( WFproc,grey) is a novel method for quantitatively estimating water resource pollution due to agricultural production. Using agricultural data accurate at the county scale,we evaluated the WFproc,greyof crops grown in the NCP from 1986 to 2010 and analyzed spatial and temporal variability. The WFproc,greyof winter wheat was found to be0. 55—2. 97 m3/ kg and that for summer maize was 0. 50—2. 02 m3/ kg; these values are significantly higher( 2—10times) than those for similar crops grown in the rest of the world,such as the U. S. and Germany. On comparing regions within the NCP,we found relatively low WFproc,greyvalues for crops grown in Hengshui,Baoding,and some regions of Hebei province,while it was high for crops grown in Bohai Bay. The total grey water volume of winter wheat and summer maize production over 25 years was estimated in the range of 2. 67 × 1010—5. 84 × 1010m3,with an average of 3. 90 × 1010m3;despite yearly fluctuations,a sustained upward trend was apparent. In light of these results,the need becomes apparent for a reduction in the amount of fertilizer used in agriculture,improvements in the efficiency of applied fertilizer,the development of new methods( such as formula fertilization by soil testing and controlled-release fertilizers),and the replacement of traditional fertilizer with organic fertilizer and biogas slurry. Water resource pollution can be further reduced by preventing fertilizer losses from surface runoff and leaching into groundwater,adopting water-saving irrigation techniques( e. g.,drip irrigation and micro irrigation with integrated water and fertilizer technology),reducing water and soil loss via straw mulching and film mulching,and increasing water storage and organic matter accumulation in subsoil.