Effects of Nitrogen Fertilizer and Crop Residues on Yield and Micronutrient Contents of Barley under ‎Deficit Irrigation

This study has been performed at the experimental farm of the College of Agriculture and Natural Resources of Darab, Shiraz University during 2017-2018 growing season. A split factorial experiment in a randomized complete block design with three replicates is carried out. The treatments include two levels of irrigation as the main plots [normal irrigation (IRN): irrigation based on the plant's water requirement up to the physiological maturity and water stress (IRDI): irrigation based on the plant's water requirement up to the anthesis stage]. Also, the first sub plot has been two levels of wheat residues [1. no residue (NR), 2. returning 30% of wheat residue to soil (RR)] and the second sub plot four fertilizer sources [N0, without fertilizer (control); N100, 100 kg N ha-1; Bio + N50, Biofertilizer (Azospirillum brasilense) + 50 kg N ha-1 and Bio, Biofertilizer (Azospirillum brasilense)]. The results show that copper, zinc, and iron contents are affected by N source × crop residue × IR regime interaction. The interaction show that the barley grain micronutrient contents have had a decreasing trend from IRN to IRDI treatment. Also, N fertilizer sources increase the micronutrient contents in both irrigation regimes, especially, in IRN conditions. The Bio + N50 treatment has increased the copper grain content by 74% and 72% as compared to N0 in NR and RR treatments, respectively, under IRN conditions. Also, there is a similar trend under IRDI conditions. Furthermore, the other grain micronutrient contents show a similar trend with barley grain copper content when affected by N source × crop residue × IR regime interaction. The highest grain yield belongs to Bio + N50 treatment under IRN (4049 kg ha-1) and IRDI (2256 kg ha-1) conditions. Therefore, due to the superiority of Bio + N50 in micronutrient contents, grain yield under different irrigation regimes and residues treatments, the principles of sustainable agriculture and environmental considerations, application of Bio + N50 treatment is recommended in southern regions of Iran.