A lysimeter study for the effects of different canopy sizes on evapotranspiration and crop coefficient of summer maize

Canopy size has an important and direct influence on water consumption by raising maize (Zea mays L.) transpiration through increased stomata number on leaves and reducing soil evaporation through blocking solar radiation. Evapotranspiration of maize was determined between 2012 and 2013 by weighing lysimeters at National experimental station for precise agriculture in Beijing. The results showed that total water consumption was 386.3 mm and 366.2 mm for maize strain with large (L) and small canopy (S), respectively. From DAS 50 to DAS 80, the difference of water consumption between two maize strains enlarged at a higher rate than other periods, which was about 4.2 mm at intervals of 10 days. Both the highest periodical water consumption and daily water consumption occurred at the Mid-stage, which was 151.8 mm for L and 139.1 mm for S, 5.06 mm/day for L and 4.64 mm/day for S, respectively. The crop coefficient was 1.11 and 1.04 and seasonal crop coefficients at Initial stage, Mid-stage and Late stage were 0.46, 1.53, 1.22 and 0.44, 1.40, 1.09 for L and S, respectively. The duration when daily Kc was bigger than 1(Kc > 1) was 56 days for L and was 5 days more than that of S, respectively. Although bigger canopy consumed more water, a higher water use efficiency of L is not only for its higher averaged yield, but also for its more positive response of yield to ET increment than that of S between two years. The stable yield performance is helpful for a long-term high water use efficiency. The characteristics of water consumption for maize of different canopy size may help to optimize water utilization in semiarid region.