Study On Alfalfa Water Footprint And Virtual Water Based On CROPWAT

Crop water footprint can reflect the real consumption of water resources in crop production,virtual water content can reflect the water use efficiency in crop production process.The calculation of crop water footprint and virtual water content can provide reference for rational planning of crop irrigation system and improving water use efficiency in crop production process.This research study the water footprint and virtual water of alfalfa in two varieties(imported varieties and Jinneng 4.1 varieties).The applicability of CROPWAT model in the calculation of water requirement of alfalfa was also studied and analyzed.Based on the application of CROPWAT model in calculating water demand of alfalfa,six provinces(Xinjiang,Gansu,Inner Mongolia,Ningxia,Hebei and Heilongjiang)of Alfalfa virtual water and water footprint was calculated.The results are as follows:(1)The water consumption of imported alfalfa and Jinneng 4.1 alfalfa in the whole growing season was similar,624.5mm and 616.1 mm,respectively.The water footprint was 7010m3/hm2 and 6926m3/hm2,respectively.According to the two alfalfa varieties tested in this study,the water consumption and water footprint of the two alfalfa varieties are close,while other alfalfa varieties need further study.(2)The water footprint of Alfalfa in different stubbles was significantly different.The total water footprint in the first stubble accounted for 55%of the total water footprint in the whole growing season,and the total water footprint in the second and third stubble accounted for 25%of the total water footprint in the whole growing season,indicating that the water resource consumption in the first stubble of Alfalfa accounted for a large proportion of the total water resource consumption in the whole growing season.A reasonable irrigation system for Alfalfa in the same cropping period combined with climate and rainfall conditions in the planting area can avoid the waste of blue water resources.(3)There are differences in virtual water content of hay among different stubbles of alfalfa.The virtual water content of hay in each stubble of two varieties of alfalfa is close.The first stubble is about 1m3/kg,the second stubble is about 0.7m3/kg,and the third stubble is about 0.6m3/kg.The virtual water content of hay decreases with the increase of harvesting times,which indicates that increasing cutting times can improve the utilization efficiency of water resources.(4)Using CROP WAT model to simulate the water requirement of two varieties of alfalfa,the simulation results show that the water requirement of imported alfalfa in the whole growing season is 644 mm,of which the first stubble is 388.3 mm,the second stubble is 139.3 mm and the third stubble is 116.4 mm;the water requirement of Jinneng 4.1 alfalfa in the whole growing season is 624.6 mm,of which the first stubble is 378.3 mm,the second stubble is 133.8 mm,and the third stubble is 112.5mm.which is in good agreement with the field test data.It shows that the CROPWAT model is suitable for the calculation of water demand in alfalfa growing period.(5)The water footprint of Alfalfa in six main high-quality alfalfa producing areas in China from high to low is Xinjiang(8075m3/hm2),Ningxia(7175m3/hm2),Inner Mongolia(6992m3/hm2),Hebei(6690m3/hm2),Gansu(6648m3/hm2)and Heilongjiang(5390m3/hm2).It can be seen that alfalfa water footprint is higher in Xinjiang,Ningxia and Inner Mongolia under the climatic conditions of each province.The water footprint of Alfalfa in Hebei and Gansu is in the middle level,while the water footprint of Alfalfa in Heilongjiang is low.(6)The virtual water content of alfalfa hay in six main high-quality alfalfa producing areas in China from high to low is Inner Mongolia(1.865m3/kg),Heilongjiang(1.326m3/kg),Hebei(1.267m3/kg),Xinjiang(1.157m3/kg),Ningxia(0.99m3/kg),Gansu(0.789m3/kg).The water use efficiency of alfalfa production in Heilongjiang and Hebei provinces is low,while that of alfalfa production in Ningxia,Gansu and Xinjiang provinces is high.(7)The pressure index of blue water resources for alfalfa production in six high-quality alfalfa producing areas in China from high to low is Ningxia(2.0222),Gansu(0.1618),Inner Mongolia(0.102),Xinjiang(0.0814),Hebei(0.0397)and Heilongjiang(0.0008).The results show that the available water resources in Ningxia can no longer meet the demand of blue water resources for alfalfa production.The amount of alfalfa planting area in the region should be reduced,the alfalfa planting area should be planned rationally according to the distribution of water resources in the region,and the drought-resistant varieties ofAlfalfa should be promoted.The water resources in Xinjiang,Inner Mongolia,Hebei and Gansu regions can meet the demand of blue water for alfalfa production,but these four areas should pay attention to the construction of irrigation facilities and improve the utilization efficiency.Promoting soil entropy-preserving technology can increase the green water utilization rate in alfalfa production;water resources in Heilongjiang region can meet the water consumption of Alfalfa in this region,and can continue to expand the scale of Alfalfa production,and promote the cultivation of high-yield alfalfa varieties.