Phosphorus availability and sugarcane yield in a calcareous soil in response to plant growth-promoting rhizobacteria (PGPR) inoculation

BACKGROUND AND OBJECTIVESLow phosphorus availability is a significant challenge in calcareous soils that are cropped to sugarcane in Khuzestan province in Iran. Although in calcareous soils the total P content may be relatively large, a major problem is the low availability of P due to the high content of calcium carbonate, which is reducing P uptake by plants. Among alternatives to overcome this limitation is the use of plant growth-promoting rhizobacteria (PGPR) that form symbiotic associations with most land plants. PGPR can improve the P availability to plant and plant yield through release of organic acids and producing numerous plant growth regulators. Therefore, the objective of this study was to evaluate the effect of inoculation with selected PGPR on P availability and sugarcane (Saccharum officinarum L.) yield in a calcareous soil located in the Debal Khozaei sugarcane agro-industry.MATERIALS AND METHODSThe experimental design was a randomized complete-block design with three replicates. Treatments consisted of ۱. Control treatment (without inoculation), ۲. Entrobacter cloacae R۳۳ and ۳. A mixture of PGPR including Entrobacter cloacae R۳۳, Staphylococcus hominis ۹E and Brevundimonas sp. Treatments were applied in second ratoon sugarcane (CP۷۳-۲۱ cultivar) using soil spray method. Population of these bacteria was ۱.۷ × ۱۰۷ CFU mL-۱ (CFU, colony forming unit). At the end of growth period, the soil available P concentration, shoot P uptake, height and cane yield were measured.RESULTS AND DISCUSSIONThe results indicated that soil available P and plant P uptake increased significantly (P<۰.۰۵) in both PGPR treatments when compared with the control. The inoculation of Entrobacter cloacae R۳۳ significantly (P<۰.۰۵) increased cane height and yield compared to the control (no PGPR). . Comparison of PGPR treatments indicated that higher cane height and yield were obtained for Entrobacter cloacae R۳۳ inoculation.CONCLUSIONIt could be concluded that inoculation of Entrobacter cloacae R۳۳ to calcareous soils with low P availability may have beneficial effects on soil P uptake by sugarcane and can potentially be an effective strategy to improve ratoon sugarcane (CP۷۳-۲۱ cultivar) yield.

Keywords:

Entrobacter cloacae R۳۳ , Microbial inoculation , Phosphorous uptake , Ratoon sugarcane