Effects of nitrogen fertilization and supplemental irrigation on bread wheat yield within the Saïs perimeter of Morocco

Abstract

Nitrogen fertilization and supplemental irrigation are key factors influencing wheat production. Understanding their combined effects is essential for sustainable agricultural practices and maximizing crop yields. In this context, the present study was conducted to determine the effect of supplemental irrigation and nitrogen fertilization on bread wheat (Triticum aestivum L.) productivity and water use efficiency under rainfed conditions in the Saïs region. The field trial was conducted during 2014-2015 cropping season. Two nitrogen doses were tested; N1: 20 kg N ha^-1 (at sowing) and N2: 145 kg N ha^-1 (with 20 kg ha^-1 at sowing, 50 kg ha^-1 in early tillering, 50 kg ha^-1 at the end of tillering and the beginning of stem extension, and 25 kg ha^-1 at the heading stage). These doses were combined with two water regimes: rainfed (I₀) and irrigated (I₁: 60 mm) at booting-heading growth stage (41 – 49 according to the Zadoks scale). Results showed that supplemental irrigation at booting-heading stage improves grain yield by 20%, number of grains by 10%, number of kernels weight by 11 % and water use efficiency by 17%, compared to rainfed conditions. Irrigation at booting-heading stage has overcome the adverse effects of hot, dry winds (Sirocco) that plague the region at the end of the crop cycle. Moreover, the application of nitrogen at a rate of 145 kg N ha^-1 resulted in a significant increase in grain yield, number of grains, kernels weight and water use efficiency by 60%, 25%, 10% and 59%, respectively, compared to the lower nitrogen dose of 20 kg ha^-1, during a crop year characterized by high rainfall. Additionally, the interaction between supplemental irrigation and nitrogen has significantly influenced all measured components. In conclusion, supplemental irrigation at booting-heading stage significantly improved grain yield and its components. Moreover, higher nitrogen doses substantially increased yield and water use efficiency, particularly when combined with supplemental irrigation. This integrated approach holds promise for sustainable wheat production in Saïs regions.