Yield and nitrogen leaching in maize field under different nitrogen rates and partial root drying irrigation

Irrigation water is limiting for crop production in arid and semi-arid areas. Furthermore, excess nitrogen (N) application is a source of groundwater contamination. Partial root drying irrigation (PRD) can be used as water saving technique and a controlling measure of groundwater N contamination. The objectives of this investigation were to evaluate the effect of ordinary furrow irrigation (OFI), variable alternate furrow irrigation (VAFI) and fixed alternate furrow irrigation (FAFI) and different N application rates (0, 100, 200, and 300 kg ha^-1) on maize yield and yield quality, drainage water, N leaching, uptake and N use efficiency (NUE). Results indicated that the interaction between irrigation treatments and N application rates was statistically significant for all treatments applied in this investigation. Maize grain yield was reduced by alternate furrow irrigation due to high sensitivity of maize to water stress, however, in case of water shortage, VAFI is superior to FAFI. In the study region, N application of 200 kg ha^-1 is optimum for maize grain yield to obtain optimum grain yield, NUE and N-yield efficiency. Drainage water and total leached nitrate decreased for VAFI and FAFI as compared to OFI and their amount were lowest for FAFI (drainage water) and in VAFI (total leached nitrate), respectively. Total leached nitrate bellow the root zone increased in response to the increase in total available nitrogen for water applications higher than crop ET. N loss was reduced for FAFI and VAFI for N application rates of 200 and 300 kg ha^-1. Only for FAFI and VAFI, the N uptake decreased and the soil residual N increased as compared with OFI. Thus, in order to avoid N loss, the amount of N fertilizer should be reduced in proportion to the amount of soil water available for plant uptake under deficit irrigation. Furthermore, it was indicated that leaf level stress sensitivity index (LLSSI) was higher for VAFI and it was about 2.5 times of OFI.