Physiological and biochemical characteristics of barley as affected by biofertilizer, crop residues and water stress

This research was carried out at the experimental farm of the Darab Agricultural and Natural Resources College of Shiraz University during 2017-2018 growing season. A split factorial experiment was layout based on a randomized complete block design with three replicates. Treatments included two irrigation levels as the main plots [1. Normal (IRN): irrigation based on the plant's water requirement up to the physiological maturity and 2. Irrigation with water stress (IRws): irrigation based on the plant's water requirement up to the anthesis stage (cutting of irrigation after anthesis)]. Also, sub plots were two levels of plant residues [1. without residue, 2. with residue: returning 30% of wheat residues to soil] and four nitrogen (N) fertilizer sources [N0, no nitrogen fertilizer (control); N100, 100 kg N ha-1; Bio + N50, Biofertilizer (Azospirillum brasilense) + 50 kg N ha-1 and Bio, Biofertilizer (Azospirillum brasilense)]. Results showed that the interaction effect of residue × N fertilizer source on chlorophylla, carotenoid, catalase and guaiacol peroxidase enzymes traits was significant. The N100 and Bio + N50 treatments significantly increased these traits compared to N0 in without residue conditions. In contrast, in the presence of residue, there was a similar trend to without residue conditions, however, the reaction of these traits to N100 and Bio + N50 supply were much more severe. The interaction of irrigation regime × N fertilizer source on catalase and guaiacol peroxidase enzymes showed that the N fertilizer application increased the amount of these enzymes, regardless of the N source, in IRN conditions. Similarly, in IRws conditions, the catalase and guaiacol peroxidase enzymes levels improved by N fertilizer supply as compared with N0, however, the intensity of their reactions to N application, especially, N100 and Bio + N50 were much more than the normal moisture conditions. The highest grain yield was achieved by Bio + N50 under IRN and IRws conditions. In general, with respect to superiority of combine N fertilizer (Bio + N50) in biochemical and grain yield traits in normal and water stress conditions and economic and environmental considerations as well, this N fertilizer regime is recommended for water availability restriction conditions in Southern regions of Iran.