Effects of irrigation and nitrogen fertilization management on crop yields and long-term dynamic characteristics of water and nitrogen transport at deep soil depths

• Published in: Soil & tillage research Vol. 198; p. 104536
• Main Authors: Xu, Jiatun, Wang, Xiaoyun, Ding, Yibo, Mu, Qing, Cai, Huanjie, Ma, Chenguang, Saddique, Qaisar
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2020
• Subjects: Deep water percolation; Groundwater contamination; N leaching transport; Nitrogen leaching; Percolation water transport; Groundwater contamination; Deep water percolation; N leaching transport; Percolation water transport; Nitrogen leaching
• ISSN: 0167-1987; 1879-3444
• DOI: 10.1016/j.still.2019.104536

•140 kg N ha−1 applied at 2 times with 75 mm irrigation was recommended for maize.•240 kg N ha−1 applied at 3 times with 90 mm irrigation was recommended for wheat.•DPW response time to 30 m depth was 1 yr (135 mm irr.) and more than 2 yr (60 mm).•Nitrogen leaching loss flux decreased exponentially with soil depth.•Higher irrigation (≥105 mm) even with lower N could cause groundwater contamination. Appropriate irrigation and nitrogen (N) management practices should be implemented to obtain high grain yields while considering the influence of water and N leaching on groundwater in the intensively cropped winter wheat (Triticum aestivum)-maize (Zea mays L.) rotation system. The calibrated RZWQM2 model was used to explore long-term (1984–2017) effects of irrigation and N fertilization on crop yield, water and nitrogen use efficiency, deep percolation water (DPW), N leaching loss (NLL), and their effects on deep soil layers (2−30 m) in this rotation system in the Jinghui Canal irrigation area of the Guanzhong Plain in China. Results showed that crop yields increased with increasing N rate. The critical N application rates of 140 and 240 kg N ha−1 coupled with 75 and 90 mm of irrigation for maize and wheat, respectively, resulted in high yields (7535 and 8977 kg ha−1), water use efficiency (2.22, 2.07 kg m-3), and nitrogen use efficiency (44.56, 40.78 kg kg−1). The simulated DPW values were 69 and 110 mm for maize and wheat, respectively, and NLL values were 25.36 and 25.47 kg ha−1. Crop yield and NLL for wheat were more sensitive to N application timing than maize yield and NLL, indicating that split N applications of two application times and three application times for maize and wheat, respectively, could be a more effective way of applying N fertilizer. DPW fluxes increased from 0.021-0.024 (varied over the 2−30 m depth) to 0.107-0.110 mm d−1 for irrigation ranging from 60 to 135 mm. The response times for DPW to be observed at the groundwater depth of 30 m could range from one year to more than two years, with DPW velocities of 0.034 and 0.077 m d−1 for 60 and 135 mm irrigation application amounts, respectively. NLL flux increased with added irrigation and N application rate, while decreasing exponentially with soil depth. Annual recharge of NO3-N to the groundwater (0.15–6.2 kg N ha−1) with lower irrigation amounts (60−90 mm) could be neglected, but higher irrigations (≥105 mm) even with lower N application rates could cause groundwater contamination. Therefore, comprehensively considering the effects of irrigation and fertilization practices on grain yields and groundwater could improve the sustainability of the agro-hydrological environment and agricultural production.