Effect of nitrogen fertilization under plastic mulched and non-plastic mulched conditions on water use by maize plants in dryland areas of China

A field experiment was conducted in a dry sub-humid area in China to study the effect of addition of five nitrogen (N) rates on evaporation (E), transpiration (T) and water use efficiency (WUE) of spring maize (Zea mays L.) with and without plastic mulch. During plant growing period, leaf area (LA), aboveground biomass and soil water stored in 200cm layer were measured about every 10 days. Results showed that without plastic mulch, N fertilization increased LA by 48% on average, aboveground biomass by 73% at harvest, and grain by 122% and the estimated T by 28% and with plastic mulch, LA, aboveground biomass and grain were increased by 58%, 47% and 143% respectively. Due to canopy shading and plant uptake, N fertilization remarkably increased T and decreased E. With plastic mulch, the transpiration use efficiency (WUET) of grain was 11.4kgha−1mm−1 without N while 19.6kgha−1mm−1 with N addition. Without plastic mulch, the evapotranspiration use efficiency (WUEET) was increased from 6.3 to 9.4, to 12.3, to 14.2, and to 14.9kgha−1mm−1 for grain, and from 18.4 to 24.3, to 29.4, to 30.5 and to 32.2kgha−1mm−1 for aboveground biomass, and WUET for grain increased from 13.3 to 15.0, to 16.4, to 18.1 and to 18.0kgha−1mm−1 when N rate increased from 0, to 30, to 60, to 90 and to 120kgNha−1, respectively. Although WUET for dry biomass was constant, about 39kgha−1mm−1, both WUET and WUEET for grain were increased with N rate until 90kgNha−1. In conclusion, N fertilization to the N deficient soil had no influence on WUET for aboveground biomass, but significantly reduced E and increased T, LA, aboveground biomass, grain yield and WUET for grain production.