Interaction Effects of Planting Method, Irrigation Regimes, and Nitrogen Application Rates on Yield, Water and Nitrogen Use Efficiencies of Winter Wheat (Triticum aestivum)

Arid and semi-arid regions in the world that produce wheat (Triticum aestivum) are faced with frequent droughts in recent years. Moreover, wheat production is highly dependent on irrigation and it is essential to increase irrigation water productivity in these regions. Therefore, the aim of this study was to investigate the effects of irrigation methods, planting methods, and nitrogen application rates on yield, water and nitrogen use efficiencies of winter wheat. The experiment arranged in split–split plot with randomized blocks with two surface irrigation methods [ordinary furrow irrigation (OFI) and variable alternate furrow irrigation (VAFI)] as the main plots, two planting methods [on-ridge planting (ORP) and in-furrow planting] as the sub plots, and three nitrogen application rates (N0 = 0, N1 = 150 and N2 = 300 kg N ha−1) as the sub–sub plot. Results indicated that VAFI reduced the winter wheat grain yield, dry matter, grain number per spike, and harvest index as 12, 9, 3, and 4%, respectively; however, these reductions were not significant in comparison with OFI method with a reduction of 33% in irrigation water; as a consequence, the straw nitrogen concentration, grain protein concentration, and also water use efficiencies (WUE), irrigation water productivity (IWP), economic irrigation water productivity (EIWP) and nitrogen use efficiency (NUE) were improved in VAFI as 14, 5, 6, 26, 25, and 8%, respectively. In spite of a slight reduction in grain yield, VAFI method increased EIWP. Economic nitrogen productivity decreased about 50% by increase in N rate, and 150 kg N ha−1 was the optimum rate to apply. Furthermore, VAFI decreased the seasonal ET, thereby improved WUE and IWP. In-furrow planting increased significantly the WUES while it did not enhance significantly WUE for grain. Generally, increasing the nitrogen rate increased the grain yield; whereas, there was no significant difference between the treatments of 150 and 300 kg N ha−1. Results suggest that application of 150 kg N ha−1 combined with in-furrow planting method and variable alternate furrow irrigation is an effective way to improve WUE, yield, yield components and NUE for winter wheat in the study area.