The Regional Variation Analysis Of Water Footprint During Summer Maize Production In Henan Province

Water resource is one of the important limiting factors which affected the development of agriculture.The researches on crop water utilization play the important role in ensuring food security.Water footprint is a new theory which clearly manifests the type,quantity and efficiency of water consumption,and provides a new method for agricultural water resource management.Our study devides Henan province into six planting regions of summer maize: eastern region,western region,southwestern region,mid-southern region,southern region and northern region.We calculated the water footprint of maize production during 1990-2015 in Henan,and analyzed its spatial-temporal variation and the composition of blue/green water.The main results are as follow:(1)The water footprint of maize production in Henan stayed at a low level after decreasing with fluctuation during 1990-2015,overall the decrease is significant and the yearly average value of water footprint of maize production is 0.97 m3·kg-1.The water footprint of maize production is in great variation among different planting regions.The highest in western region of Henan is 56.6% which is above the total average,while the eastern,mid-southern and northern of Henan have lower water footprint than average.The water footprint of maize production in western and mid-southern Henan decreased significantly,while the decrease in other planting regions of Henan was not significant.The decrease in water footprint of maize production in each planting region mainly occurred in 2000 s.As time goes by,the differences in water footprint of maize production in each planting region of Henan gradually decreased.(2)The average value of the blue and green water footprint of maize production in Henan during 1990-2015 were 0.13 m3·kg-1 and 0.85 m3·kg-1,respectively.The blue and green water footprint of maize production both decreased significantly.The major portion(80%)of the water footprint during maize production is contributed by green water.For the temporal and spatial distribution,green water ratio was negatively connecting with the precipitation during maize growth period,the lower the precipitation during maize growth is,the higher green water ratio would be.(3)The water footprint of maize in Henan increased with fluctuation during 1990-2015 and the yearly average value is 11.1 billion m3.The water footprint of maize mutated in 2007 and began to increased significantly thereafter.In each planting region,the water footprint of maize increased significantly during 1990-2015,mutated in 2000 s and then increased significantly.There are significant spatial differences in the water footprint of maize in each planting regions,with higher levels in northern,eastern and mid-southern of Henan,and lower levels in western and southern of Henan.The blue and green water footprint of maize in the whole province and each planting regions increased significantly entirely.The ratio of maize blue water footprint to agricultural water usage increased significantly in the whole province and in each planting regions,which indicating that the proportion of maize irrigation in agricultural water usage was increasing.(4)Relative humidity,which was the dominant factor influencing the water footprint of summer maize production in Henan,was negatively correlated with the water footprint of maize production.The average temperature,sunlight hours,and wind speed were positive meteorological factors that have the significant impacts on the water footprint of maize production.The effective irrigation ratio,the pesticides usage amount per hectare,and the fertilizer usage amount per hectare were the production factors that have the great impacts on the water footprint of maize production in Henan.The dominant factor influencing the water footprint of maize production in eastern,western,southwestern,mid-southern and southern of Henan was relative humidity,while in northern of Henan was the effective irrigation ratio.In western of Henan,the wind speed and agricultural machinery power per sown area were negatively correlated with the water footprint of maize production,while in other regions was positively correlated.(5)Based on the water footprint of maize production and distribution of water resource,we proposed the following preliminary recommendations for maize production in Henan Province.As green water is the main source for agricultural water usage in Henan,green water resources must be used reasonably,adequately and efficiently.We must pay attention to rational and correct use of chemical fertilizers and pesticides,and achieve high yields based on water-saving and fertilizer-saving.In each planting regions,the different measures should be taken based the local dominant factor influencing the water footprint of summer maize production.The government should play a role in stabilizing the price of maize and setting the price of water reasonably.