Effect of Plant Growth-Promoting Rhizobacteria (Enterobacter cloacae) on Uptake and Uptake Efficiency of Potassium in Sugarcane (Saccharum officinarum L.)

Intensive cropping of sugarcane and no application of potassium (K) fertilizer resulted a reduction of K pools in the soil. In order to evaluate the potassium uptake efficiency in two different fertilizer managements, new plantation of sugarcane and ratoon, and to investigate the effect of indigenous plant growth-promoting rhizobacteria on potassium uptake, a pot experiment with three replications was carried out in greenhouse condition. Treatments were the combination of two P rates (including: blank (P0) and 200 kg/ha (P200)), and two plant growth-promoting rhizobacteria strains (including: Enterobacter cloacae R13 (B13) and Enterobacter cloacae R33 (B33)). The morphological characteristics of sugarcane and root and potassium in the rhizosphere were evaluated at three harvesting times (60, 95 and 140 days after planting (DAP)). In management similar to plantation of sugarcane, higher K uptake and influx were found in P200B0 and P200B13 treatments, while the highest root length was observed in P200B33 treatment. In management like to ratoon, the greatest K uptake and influx were observed in P0B33 treatment. At the second harvesting period (between 95 and 140 DAP), K influx decreased severely in P0R0 treatment in comparison with the first harvesting period, while it was not occurred in the inoculated treatments. Therefore, in new sugarcane plantation condition, Enterobacter cloacae R13 improved K uptake efficiency, while in ratoon stage, Enterobacter cloacae R33 abled to increase uptake and uptake efficiency of K. Also, the result showed that the influx was the main mechanism of K uptake in sugarcane in inoculated treatments.