LAUSR

Water and nitrogen (N) are generally two of the most important factors in determining the crop productivity. Proper water and N managements are prerequisites for agriculture sustainable development in arid areas. Field experiments were conducted to study the responses of water productivity for crop yield (WPY-ET) and final biomass (WPB-ET) of film-mulched hybrid maize seed production to different irrigation and N treatments in the Hexi Corridor, Northwest China during April to September in 2013 and also during April to September in 2014. Three irrigation levels (70%–65%, 60%–55%, and 50%–45% of the field capacity) combined with three N rates (500, 400, and 300 kg N/hm2) were tested in 2013. The N treatments were adjusted to 500, 300, and 100 kg N/hm2 in 2014. Results showed that the responses of WPY-ET and WPB-ET to different irrigation amounts were different. WPY-ET was significantly reduced by lowering irrigation amounts while WPB-ET stayed relatively insensitive to irrigation amounts. However, WPY-ET and WPB-ET behaved consistently when subjected to different N treatments. There was a slight effect of reducing N input from 500 to 300 kg/hm2 on the WPY-ET and WPB-ET, however, when reducing N input to 100 kg/hm2, the values of WPY-ET and WPB-ET were significantly reduced. Water is the primary factor and N is the secondary factor in determining both yield (Y) and final biomass (B). Partial factor productivity from applied N (PFPN) was the maximum under the higher irrigation level and in lower N rate (100–300 kg N/hm2) in both years (2013 and 2014). Lowering the irrigation amount significantly reduced evapotranspiration (ET), but ET did not vary with different N rates (100–500 kg N/hm2). Both Y and B had robust linear relationships with ET, but the correlation between B and ET (R2=0.8588) was much better than that between Y and ET (R2=0.6062). When ET increased, WPY-ET linearly increased and WPB-ET decreased. Taking the indices of Y, B, WPY-ET, WPB-ET and PFPN into account, a higher irrigation level (70%–65% of the field capacity) and a lower N rate (100–300 kg N/hm2) are recommended to be a proper irrigation and N application strategy for plastic film-mulched hybrid maize seed production in arid Northwest China.