Date of this Version
Agricultural Water Management 287 (2023) 108421. https://doi.org/10.1016/j.agwat.2023.108421
While the impact(s) of irrigation and nitrogen (N) levels on crop yields have been investigated separately, research lacks about how different irrigation methods coupled with different N application timing strategies under full and limited irrigation levels effect yield, soil nitrate nitrogen (NO3-N) residual and stover N uptake. Knowledge of these dynamics can help to establish effective water and N management guidelines for the same crop under different irrigation methods and irrigation levels. This research investigated maize (Zea mays L.) residual soil NO3-N concentration and stover and grain N uptake response to water under different irrigation methods [center pivot (CP), subsurface drip irrigation (SDI) and surface (furrow) irrigation (FI)] simultaneously. Three irrigation levels were imposed: (i) full irrigation treatment (FIT), (ii) limited irrigation (80% FIT and 60% FIT) and (iii) rainfed treatment (RFT). N treatments were: (i) traditional (TN) treatment in which seasonal N requirement was applied in spring as a pre-plant, (ii) non-traditional-1 (NT-1) in which 30% of the seasonal required N was applied as spring pre-plant, 40% and 30% as side-dress at V8 (8-leaf collar) and VT/VR (tasseling/ silking) stages, respectively, and (iii) non-traditional-2 (NT-2) in which 25% of the seasonal required N was applied as spring pre-plant, 25%, 30% and 20% as side-dress at V8, VT/VR and R3 (i.e., kernel, milk) stages, respectively. The highest NO3-N residual was observed in the topsoil and residual NO3-N was more pronounced in the RFT followed by limited irrigation levels. The highest average stover N concentration, regardless of N treatments, was in the order of FI (1.99%)>SDI (1.94%)>CP (1.73%). Overall, irrigation levels significantly influenced (p < 0.05) seasonal stover N uptake in both growing seasons, regardless of N treatments and irrigation methods. In most cases, the highest seasonal stover N uptake was observed in the FIT and/or 80% FIT and the lowest values were observed with RFT. Grain N concentrations were higher in NT-1 and NT-2 than TN in SDI, whereas the CP seasonal grain N concentration had opposite trends with both NT-1 and NT-2 having higher seasonal grain N concentration than TN. The highest grain N uptake was observed in the SDI-NT-1, followed by CP-NT-2 and FI-TN under limited irrigation treatments. The coupled irrigation and N treatments of 80% FIT-NT- 2-CP, 60% FIT-NT-1-SDI and 80% FIT-NT-2-SDI had ≥ 5 mg kg-1 residual NO3-N in the 0.60 m soil layer in drier year in 2016. The trend was opposite in wetter year in 2017 and there was an increasing NO3-N content trend (≥5 mg kg-1) in the 0.60–1.20 m soil layer. The highest NO3-N concentrations were observed in the RFT, NT-1, and NT-2 across irrigation methods, indicating that the irrigation management and in-season N application treatments significantly (p < 0.05) influenced the NO3-N magnitudes. Soil residual NO3-N had quadratic relationship with the seasonal total soil water supply; and soil residual NO3-N increased with decreasing total water supply. The quantitative analyses presented here can aid to improve N and water productivity and reduce unnecessary applied N in for maize under the conditions similar to those presented in this research.