Irrigation and Nitrogen Regimes Promote the Use of Soil Water and Nitrate Nitrogen from Deep Soil Layers by Regulating Root Growth in Wheat

• Published in: Frontiers in plant science Vol. 9; p. 32
• Main Authors: Liu, Weixing, Ma, Geng, Wang, Chenyang, Wang, Jiarui, Lu, Hongfang, Li, Shasha, Feng, Wei, Xie, Yingxin, Ma, Dongyun, Kang, Guozhang
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 01.02.2018
• Subjects: grain yield; irrigation regime; nitrogen regime; Plant Science; root length density; soil NO3-N content; water use; soil NO3-N content; water use; nitrogen regime; root length density; grain yield; irrigation regime
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2018.00032

Unreasonably high irrigation levels and excessive nitrogen (N) supplementation are common occurrences in the North China Plain that affect winter wheat production. Therefore, a 6-yr-long stationary field experiment was conducted to investigate the effects of irrigation and N regimes on root development and their relationship with soil water and N use in different soil layers. Compared to the non-irrigated treatment (W0), a single irrigation at jointing (W1) significantly increased yield by 3.6-45.6%. With increases in water (W2, a second irrigation at flowering), grain yield was significantly improved by 14.1-45.3% compared to the W1 treatments during the drier growing seasons (2010-2011, 2012-2013, and 2015-2016). However, under sufficient pre-sowing soil moisture conditions, grain yield was not increased, and water use efficiency (WUE) decreased significantly in the W2 treatments during normal precipitation seasons (2011-2012, 2013-2014, and 2014-2015). Irrigating the soil twice inhibited root growth into the deeper soil depth profiles and thus weakened the utilization of soil water and NO -N from the deep soil layers. N applications increased yield by 19.1-64.5%, with a corresponding increase in WUE of 66.9-83.9% compared to the no-N treatment (N0). However, there was no further increase in grain yield and the WUE response when N rates exceeded 240 and 180 kg N ha , respectively. A N application rate of 240 kg ha facilitated root growth in the deep soil layers, which was conducive to utilization of soil water and NO -N and also in reducing the residual NO -N. Correlation analysis indicated that the grain yield was significantly positively correlated with soil water storage (SWS) and nitrate nitrogen accumulation (SNA) prior to sowing. Therefore, N rates of 180-240 kg ha with two irrigations can reduce the risk of yield loss that occurs due to reduced precipitation during the wheat growing seasons, while under better soil moisture conditions, a single irrigation at jointing was effective and more economical.