Study On The Effects Of Different Application Amount Of Chemical Fertilizer On The Water Footprint Of Maize Production

Water is the material basis of all living things and an important part of natural resources.At present,China's agricultural water use accounts for more than 60% of the total water use,among which farmland irrigation water accounts for 90% of the agricultural water use.Water resources has gradually become more significant to the restriction role of agricultural production,and the wide use of pesticides,fertilizers,and other chemicals leads to increasingly serious situations of water environment issues.Therefore,how to protect water resources and water environment,and how to rationally plan and evaluate water resources are of great significance.In the past,without considering the use of soil water by crops and the water pollution caused by crops growing,irrigation water was often considered as the main index in the evaluation of agricultural water.Crop water footprint not only can assist in checking the amount of water used in crop production,but also can help to take the consumption of water resources caused by diluting agricultural pollution into consideration,providing theoretical bases for solving water shortages.Nowadays,there are so many studies on water footprint accounting,spatial and temporal differentiation,evaluation and influencing factors in the research of water footprint of crop production,but less research on the field experiment.Moreover,for the accounting of grey water footprint,only the nitrogen emission from chemical fertilizers is considered in general.In order to determine the actual water use and water consumption structure in corn production after the chemical fertilizer reduction,this paper takes the basic farmland protected area in Wezigou village,Nong'an county,Jilin province as the research area,and four experimental treatments are set up(normal fertilization,minus 15%,minus 30%,minus 45%).On the basis of the theory of water footprint,this paper explores the effect of different amount of fertilizer on water consumption and water pollution in the process of maize growth,and analyzes the change of green water footprint,blue water footprint,and grey water footprint.This study help provide the base for further enriching,developing the water footprint theory,and improving the evaluation of water resources and water environment.The main conclusions of this study are as follows:(1)The average blue water footprint in the growing period of maize in 2018 and2019 is 3.38 m3/t and 3.32 m3/t respectively.The difference in the two-year blue water footprint is tiny.In the two-year field experiment,the blue water footprint of 45%plots is the largest,while 30% plots are the smallest in 2018 and 15% plots are the smallest in 2019,which is mainly affected by the amount of sowing with water andcorn yield in the planting period.(2)The average green water footprint in the growing period of maize in 2018 and2019 is 349.94 m3/t and 414.29 m3/t respectively.In the two-year field experiment,the green water footprint of the 45% plot is the largest,while the green water footprint of the 30% plot was the smallest in 2018 and the green water footprint of the 15% plot was the smallest in 2019.(3)The average grey water footprint of the experimental plots in the growing period of maize in 2018 and 2019 is 8.13 m3/t and 13.73 m3/t respectively.The average grey water footprint of each plot in 2019 is 1.69 times that of each plot in2018.This is because the contribution rate of the grey water footprint generated by the second surface runoff in 2019 to the grey water footprint is relatively large,with a value of 8.72 m3/t.The largest pollutants TN and TP appeared in all the previous field runoff tests in two years,especially TN,with the highest frequency.Therefore,in the prevention and control of agricultural diffuse pollution,the runoff pollution caused by heavy rainfall and excessive application of nitrogen fertilizer should be paid more attention.From the perspective of different fertilizer application amounts,the grey water footprint of the 15% plot,30% plot and 45% plot reduced by 25.57%,24.68%and 31.66% respectively,compared with that of the normal fertilization plot in 2018.In 2019,the grey water footprint of 15% plots,30% plots and 45% plots reduced by60.94%,71.96% and 68.34% respectively,compared with that of normal fertilization plot.(4)The average total water footprint in the growing period of maize in 2018 was361.45 m3/t,with green water footprint accounting for 96.82%,blue water footprint accounting for 0.93%,and grey water footprint accounting for 2.25%.In 2019,the average water footprint of corn growing in the test plot was 431.33 m3/t,with green water footprint accounting for 96.05%,blue water footprint accounting for 0.77% and grey water footprint accounting for 3.18%.The two-year field experiment shows that green water footprint accounts for the largest proportion,which is more than 96%,followed by grey water footprint,and blue water footprint is the least.In terms of applyingquantity of chemical fertilizer the total water footprint of corn in the 45% plot was the largest,followed by the normal fertilization plot,and the total water footprint of corn in the 15%-30% plot was relatively low.