Effects of irrigation and urea types on water use efficiency of maize

Water and nitrogen managements are both very important to increase crop yields. For the sake of discussing the effects of irrigation and urea types (normal urea and controlled release urea) on soil water content, kernel filling rate and water use efficiency of maize (Zea Mays L.), an experiment was carried out in a randomized design. Each urea type was used at two nitrogen levels, which were 75 kg/hm2 and 150 kg/hm2, with no nitrogen used as control respectively. Two irrigation levels, no irrigation in the whole growth duration and irrigated 85 mm at grain filling stage, were designed. The results showed that, at the same level of irrigation and nitrogen, soil water contents in 0-140 cm layer of maize applied with controlled release urea (CU) were higher (P<0.05) at pre-tasselling stage, but lower at maturity stage, than those applied with normal urea (NU), which can be named as an effect of “store water at early stage in soil and use it at late stage (SEUL)”. Compared with NU, CU could significantly increase kernel filling rate, water use efficiency (WUE), and yield increased efficiency by irrigation (IEI). WUE and IEI of the treatments applying nitrogen at 150 kg/hm2 were higher than those applying at 75 kg/hm2. Compared to no irrigation, irrigation reduced the WUE, but increased kernel filling rate and grain yield. CU coupling effect with soil water was higher than that of NU, which could increase the yield and WUE of maize simultaneously. Further analysis of the results showed that, the increases of WUE and IEI of CU were mainly resulted from SEUL effect and higher kernel filling rate. This research provides academic and instructive meanings for high yield and water use efficiency of maize in subhumid regions.