Improved Phosphorus (P) Uptake and Yield of Rainfed Wheat Fed with P Fertilizer by Drought-Tolerant Phosphate-Solubilizing Fluorescent Pseudomonads Strains: a Field Study in Drylands

Abstract

Application of phosphate-solubilizing bacteria (PSB) to improve phosphorus (P) nutrition of plants under conditions of P deficit in soil has been frequently studied in controlled conditions. However, little research attention has been paid to studying the combined effects of PSB and P fertilizer on improving P uptake and yield of rainfed wheat plant under natural conditions in arid and semi-arid regions including drylands. Field experiments were arranged in a randomized complete block design with a 3 × 4 × 2 × 2 factorial arrangement of treatments with three replications during years 2017–2018 (Y1) and 2018–2019 (Y2) (at four fields) at two various locations (Qazvin and Zanjan). Experimental treatments included P fertilizer factor at three levels: no fertilizer (P0), triple superphosphate (TSP) fertilizer at 10 kg P ha−1 (P10), and TSP fertilizer at 20 kg P ha−1 (P20) and four variants of PSB factor: no inoculation (B0), inoculation with Pseudomonas baetica B21 (B1), inoculation with Pseudomonas helmanticensis B30 (B2), and co-inoculation with B21 and B30 (B3). The results of this study showed that the growth indices and P nutrition of rainfed wheat in dryland fields were affected by the time and location of planting. The application of 20 kg P ha−1 and single inoculation and co-inoculation of wheat with bacterial strains had a significant (p ≤ 0.05) impact on reduced electrolyte leakage. However, the application of 20 kg P ha−1 and single inoculation and co-inoculation of wheat with strains B21 and B30 showed a significant (p ≤ 0.05) effect on increased relative water content, chlorophyll index, proline content, plant height, shoot dry weight, thousand grain weight, and the concentration of shoot and grain P. As a result, application of 20 kg P ha−1 and single inoculation and co-inoculation of wheat with strains B21 and B30 increased grain yield by 63, 43, 52, and 58%, respectively. However, the pattern of these fluctuations differed in different years and locations. The significant enhancement of biomass parameters and grain yield of rainfed wheat by co-inoculation of PSB in combination with 20 kg P ha−1 strongly supports the use of Pseudomonas strains as a biofertilizer for improving the wheat growth and grain yield in rainfed farming systems. The results of this study also highlight the importance of simultaneous introduction of phosphate fertilizer and PSB for improving plant performance under drought stress.