Study On Monitoring And Calculation Method Of Water Consumption Of Seed Maize In Arid Region Of Northwest China

There is extreme shortage of water resources in the arid region of Northwest China andthe contradiction between water use in agriculture and ecology is obvious. Accuratemeasurement and estimation of crop water consumption is essential to the development ofscientific irrigation system and efficient use of limited water resources. Therefore, themonitoring and calculation of crop water consumption is an important research topic. Theresearch was conducted at Shiyanghe Experimental Station for Water-saving in Agricultureand Ecology, China Agricultural University, located in Gansu Province of Northwest China in2011. The object of the study was the typical crop of the region-seed maize. Lysimetermethod, eddy covariance method, bowen ratio-energy balance method and the water balancemethod were carried out to continuously monitor the water consumption in the whole growthperiod of seed maize. The main results are outlined as follow:(1) Water balance method as basis, lysimeter method overestimated ET by12.8%in thewhole growth period of seed maize, eddy covariance method was5.4%undervalued, theresults of bowen ratio method was closer. Lysimeter method significantly overestimated ET inheading and filling stage, bowen ratio method significantly overestimated in the seedlingstage. In contrast, eddy covariance method can more accurately reflect the process of thechange of ET in the growing period of seed maize.(2) Plastic film mulching can improve soil water and heat conditions, thus promote cropgrowth and development. Plastic film mulching increased crop transpiration and reduced soilevaporation, and the reduction of soil evaporation was greater than the increase of the croptranspiration. So the total water consumption of the seed maize was reduced after mulching.(3) The three largest factors affected30min latent heat fluxes of seed maize field are netradiation, air temperature and vapor pressure deficit. The three largest factors affected dailylatent heat fluxes are net radiation, air temperature and leaf area index. Latent heat fluxestimation formulas in30min scale and daily scale were established based on the analysis ofthe response relationship between latent heat fluxes and their impact factors.(4) The crop coefficients of mulching seed maize in Northwest China were respectively0.40,1.00,1.13,1.05and0.90in seedling, jointing, heading, grain filling and maturity stage. The average crop coefficient of the whole growth period was0.83. There was significantopening down parabolic relationship between crop coefficient and days after seeding andsignificant logarithmic relationship between crop coefficient and leaf area index.