Improved Growth and Nutrition of Sorghum (Sorghum bicolor) Plants in a Low-Fertility Calcareous Soil Treated with Plant Growth–Promoting Rhizobacteria and Fe-EDTA

Abstract

The low availability of micronutrients such as zinc (Zn) and iron (Fe) and macronutrients (phosphorus (P), in particular) in calcareous soils adversely affects plants such as sorghum (Sorghum bicolor) that are highly sensitive to deficiencies of these elements. This study investigated the potential effects of different Fe chelates and plant growth–promoting rhizobacteria (PGPR) on nutrition and growth of sorghum plants growing in a low-fertility calcareous soil. A glasshouse experiment was carried out in a completely randomized design with four PGPR treatments (Pseudomonas putida P159, Pseudomonas fluorescens T17-24, Bacillus subtilis P96, and an uninoculated control), and three Fe treatments (10 mg Fe kg−1 soil as Fe-EDDHA or Fe-EDTA, and no Fe application). Application of both Fe chelates (Fe-EDDHA and Fe-EDTA) increased plant dry weight, shoot content, and concentration of Zn and Cu (copper) compared with the control treatment; however, Fe-EDTA was found to be more effective than Fe-EDDHA. Fe-EDTA significantly increased the concentration of Cu, Zn, and Mn (manganese) up to 74.7%, 40.3%, and 30.6% in the rhizosphere, respectively. The use of PGPR significantly increased plant growth as well as the content of Mn, Zn, Cu, and K (potassium) compared with the uninoculated plants. Overall, the Fe-EDTA chelate was more effective in increasing nutrient uptake and growth of sorghum plants than Fe-EDDHA because of its low chemical stability at high pH. Combined application of Fe-EDTA and PGPR strains provided the greatest growth and nutritional benefits to sorghum plants growing in the alkaline nutrient-deficient calcareous soil.