A Lysimeter Study For The Characteristic Of Water Consumption Of Summer Maize

In this study, characteristics of water consumption of summer maize was measured by24weighing lysimeters in North China Plain (NCP), the comparison of maize water consumption characteristicsbetween two plant types and two densities was conducted simultaneously, the relationship between Leaf Area Index and crop coefficient was established by an equation, the correlativity of daily meteorological factors and daily water consumption was also analyzed. The main results showed:1. The amount of total water consumption of maize was410.6mm,38.7%of total water sonsumption was occupied during R1-R4, respectively, and45.2%of total water sonsumption was occupied in August. The ratio of water consumption of two periods partitioned by silking was46:54. The averaged amount of water consumption in five days was19.9mm. Daily water consumption presented an unimodal pattern, rised in a linear form from jointing stage to silking stage, arrived its peak at stage from silking to grain filling, which was6.6mm d-1. The ratio of water consumption between daytime and nighttime was18:1. The water consumption rate began to rise from6:00, and its apex appeared at12:30-13:00, and slightly rised again for half an hour after a decline lasting about two or three quarters, the downtrend of water consumption rate endured from15:00to18:00, then its fluctuation kept feeble till the6:00next day.2. Total water consumption of maize with big plant type was28.5mm more than the small type,5days water consumption of maize with big plant type was1.3mm more than the small plant type, the difference of monthly water consumption between two types averaged for5.6mm, its crest value occurred in August with a difference of12.9mm, similar to biggest difference of stage water consumption happened in stage from silking to mid filing, which was14.7mm. The discrepancies of water consumption between two plant types before and after silking stage was10.3mm and18.2mm, respectively. The summit time of water consumption rate appeared in12:30-13:00, maize with big plant type showed higher water consumption rate than the small type at the summit time through whole growth stage, and the higher propotion was16.9between two types at the stage from silking to mid-filling.3. Total water consumption increased by55.0mm in pace with the density rising from6plant m-2to8plant m-2, monthly water consumption and5-days water consumption increased by10.9mm and3.6mm, respectively. August was the month that biggest discrepancy of monthly water consumption between two densities occurred, with an amount of30.8mm, which is bigger than the discrepancy of stage water consumption between two densities occurred in stage from V12-VT, with an amount of20.6mm. The max discrepancy value of daily water consumption between two densities was1.20mm d-1at the stage from V13-VT, which was also the biggest difference of water consumption rate happened.4. The development of LAI was an unimodalcurve, during the period from V13to silking, water consumption rised77.2mm for maize with big plant type synchronized with each1m2of LAI enlargements well as89.2mm for maize with small plant type,84.8mm for maize under8plant m-2and84.8mm for maize under6plant m-2,respectively. At the time of13:00-14:00, photosynthsis rate and water consumption rate decreased for both plant types and densities before silking, however, photosynthsis rate descended while water consumption rate rised at the same time after silking, the two rates mentioned above rised under high plant density and decreased under low density. Compared to maize with small plant type, the big type exhibited a higher yield potential and water use efficiency, higher WUE appeared under lower density for same plant type.5. Local Crop coefficient was1.00, which calculated by the Priestley-Taylor equation resulted from its fine performance ofestimation on local reference evapotranspiration. Four crop coefficients of different periods according to the FAO classification was0.40,1.03,1.30and1.13, respectively. The impact of meteorologic factors on daily water consumption was influenced by density. Both two plant types showed concordant trend:increased density weakened the promotion of radiation on daily water consumption, also enhanced the inhibition of precipitation and daily humidity on daily water consumption.