Hadi Asadi Rahmani

The indiscriminate use of hazardous chemical fertilizers can be reduced by applying eco-friendly smart farming technologies, such as biofertilizers. The effects of five different types of plant growth-promoting rhizobacteria (PGPR), including Fla-wheat (F), Barvar-2 (B), Nitroxin (N1), Nitrokara (N2), and SWRI, and their integration with chemical fertilizers (50% and/or 100% need-based N, P, and Zn) on the quantitative and qualitative traits of a rainfed wheat cultivar were investigated. Field experiments, in the form of randomized complete block design (RCBD) with four replications, were conducted at the Qamloo Dryland Agricultural Research Station in Kurdistan Province, Iran, in three cropping seasons (2016–2017, 2017–2018, and 2018–2019). All the investigated characteristics of rainfed wheat were significantly affected by the integrated application of PGPR chemical fertilizers. The grain yield of treated plants with F, B, N1, and N2 PGPR plus 50% of need-based chemical fertilizers was increased by 28%, 28%, 37%, and 33%, respectively, compared with the noninoculated control. Compared with the noninoculated control, the grain protein content was increased by 0.54%, 0.88%, and 0.34% through the integrated application of F, N1, and N2 PGPR plus 50% of need-based chemical fertilizers, respectively. A combination of Nitroxin PGPR and 100% of need-based chemical fertilizers was the best treatment to increase the grain yield (56%) and grain protein content (1%) of the Azar-2 rainfed wheat cultivar. The results of this 3-year field study showed that the integrated nutrient management of PGPR-need-based N, P, and Zn chemical fertilizers can be considered a crop management tactic to increase the yield and quality of rainfed wheat and reduce chemical fertilization and subsequent environmental pollution and could be useful in terms of sustainable rainfed crop production.

Salinity is a major environmental stress that limits plant production and portraits a critical challenge to food security in the world. In this research, the impacts of plant growth–promoting bacteria (Pseudomonas RS-198 and Azospirillum brasilense RS-SP7) and foliar application of plant hormones (salicylic acid 1 mM and jasmonic acid 0.5 mM) on alleviating the harmful effects of salt stress in rapeseed plants (Brassica napus cv. okapi) were examined under greenhouse condition. Salt stress diminished rapeseed biomass, leaf area, water content, nitrogen, phosphorus, potassium, calcium, magnesium, and chlorophyll content, while it increased sodium content, endogenous salicylic and jasmonic acids, osmolyte production, H₂O₂ and O₂^•− generations, TBARS content, and antioxidant enzyme activities. Plant growth, nutrient content, leaf expansion, osmolyte production, and antioxidant enzyme activities were increased, but oxidative and osmotic stress indicators were decreased by bacteria inoculation + salicylic acid under salt stress. Antioxidant enzyme activities were amplified by jasmonic acid treatments under salt stress, although rapeseed growth was not generally affected by jasmonic acid. Bacterial + hormonal treatments were superior to individual treatments in reducing detrimental effects of salt stress. The best treatment in rectifying rapeseed growth under salt stress was combination of Pseudomonas and salicylic acid. This combination attenuated destructive salinity properties and subsequently amended rapeseed growth via enhancing endogenous salicylic acid content and some essential nutrients such as potassium, phosphorus, and magnesium.

This factorial experiment consists of four levels of sulfur+Thiobacillus and three levels of triple superphosphate arranged in a completely randomized block design in three regions. With an increased sulfur+Thiobacillus and phosphorus (P), grain yield, phosphorus, iron (Fe), and zinc (Zn) uptake of canola increased in Qom and Mazandaran. Combined treatments of S₂₀₀₀T₄₀ and P_100% showed these properties most. In Safiabad, S₁₀₀₀T₂₀ resulted in a significant increase of P, Fe, and Zn uptake of canola, and no significant effect was found on the grain yield. The highest Fe and Zn concentrations in Qom soil was measured in S₂₀₀₀T₄₀. In Safiabad, maximum Fe concentration in soil was registered by S₁₀₀₀T₂₀ and P_65%. The minimum soil pH of Qom and Mazandaran was recorded by S₁₀₀₀T₂₀ and S₂₀₀₀T₄₀, respectively. The effect of sulfur and Thiobacillus on nutrients uptake and canola yield was good and indicates its potential for alleviating the impacts of calcareous soils.