Theoretical Irrigation Efficiency And Water Saving Potential Of Main Crops In China

China is a large agricultural country.The agricultural production is the basis of the national economy.Water resource is the one of the important limiting factors for the agricultural development,and it is also the resource support and guarantee for agricultural production.The serious waste of irrigation water is existing in our country,and the efficiency of irrigation water use is low and the water has potential large saving.In this paper,the irrigation efficiency and the water saving potential of main crops in China are taken as research objects.The theoretical water productivity,theoretical irrigation efficiency and water saving potential of summer maize,spring maize,winter wheat,single cropping rice and double cropping rice were calculated in their planting area.The spatial distribution characteristics of theoretical water productivity,the theoretical irrigation efficiency and the water saving potential and the interannual variation rate of theoretical water productivity were discussed.The main contents and conclusions are as follows:(1)The theoretical water productivityBased on the collection of meteorological data,the light-temperature production potential and crop water requirement of major crops in their planting regions were measured.Based on this,we calculated the theoretical water productivity and analyzed the law of spatial distribution and time change.The conclusions are as follows:The theoretical water productivity of the summer maize is the largest(4.10kg/m~3),the single cropping rice and double early cropping rice is the smallest(2.55 kg/m~3).In terms of spatial distribution,the theoretical productivity of summer maize mostly shows a trend of high south and low north.There is no obvious law of theoretical water productivity in the spring maize.The theoretical water productivity of winter wheat tend to be high in the south and low in the north.The theoretical water productivity of double cropping early rice is higher in the East and West,and lower in the central region,and the theoretical water productivity is high in the West and low in the East in the double cropping late rice.In single season rice,the average theoretical water productivity of central China rice are the largest,and the theoretical water productivity of the southwest single season rice are slightly smaller,and the theoretical water productivity of the Northeast single season rice are the smallest.The theoretical water productivity of main crops increased except for double cropping late rice during the period from 1964 to 2014.The average theoretical water productivity of winter wheat increased(16.60%),the average theoretical water productivity of spring maize was 15.11%,and the average theoretical water productivity of early rice was the lowest(0.56%).The average theoretical water productivity of double cropping late rice decreased by 1.61%.(2)The efficiency of theoretical irrigationAccording to the calculated theoretical water productivity and the actual water productivity obtained by the literature survey,the concept and calculation method of the theoretical irrigation efficiency are proposed in this paper.According to the calculation results,the average theoretical irrigation efficiency of spring maize were the highest(65.73%),and the average theoretical irrigation efficiency of the double season late rice were the lowest(46.42%).In terms of spatial distribution,the spatial distribution of irrigation efficiency of summer maize is not obvious,while the spatial distribution of theoretical irrigation efficiency of spring maize generally increased from east to west and then decreased gradually.The spatial distribution of irrigation efficiency of winter wheat is not obvious.The average value of theoretical irrigation efficiency in the single season rice area in Central China is the smallest,the southwest single season rice area is slightly larger and the Northeast single season rice area is the largest.(3)The potential of water savingBased on the actual water productivity and the theoretical water productivity of crops the amount of saving water per unit production can be calculated.the amount of water that can be saved by the main crops produced per unit of production.In addition,based on the proportion of water-saving potential that were calculated by the theoretical irrigation efficiency and combining the quotas of irrigation water in various regions.The conclusions are as follows:Double cropping early rice has the greatest potential of saving water per unit yield(0.53m~3/kg),and the lowest yield per unit area of Spring Maize(0.20 m~3/kg).The proportion of summer maize,winter wheat and double cropping rice is more than 50%,and the ratio of water saving potential of spring maize and single cropping rice is more than 35%.The average irrigation water for summer maize is least(634.47 m~3/hm~2),and the average irrigation water for double cropping late rice is the most(2873.47 m~3/hm~2).