Effect of phosphate solubilising bacteria (Enterobacter cloacae) on phosphorus uptake efficiency in sugarcane (Saccharum officinarum L.)

Abstract

Phosphorus (P) is an essential nutrient in sustainable production of sugarcane. Due to low labile P in soil under sugarcane cultivation, evaluation of the efficiency of P uptake and the application of phosphate solubilising bacteria (PSB) play important roles in management of P fertiliser. To investigate the effect of using PSB on P uptake in sugarcane (variety CP57–614), a pot experiment was conducted with three replications in greenhouse conditions. The treatments were a combination of three P rates (0 (P0), 50 and 100% (~40 mg kg−1) as triple superphosphate, and two PSB strains (Enterobacter cloacae R13 (R13) and R33 (R33)) which were applied independently and simultaneously. Morphological characteristics of sugarcane and some biochemical parameters were evaluated in the rhizosphere at three harvesting times: 60, 95 and 140 days after planting (DAP). Whereas in low available P (P0), bacterial strain R33 improved P uptake along with sugarcane ageing, P uptake was diminished in non-inoculated treatment over time. Activity of PSBs in the rhizosphere (especially strain R33) prevented the sharp fall of P influx after 95 DAP in low available P condition. Indeed, activity of R33 in the rhizosphere decreased the dependence of P uptake on root development via improving P uptake. Therefore, influx was the main mechanism of P uptake in sugarcane. Sugarcane inoculated by PSBs acquired 76 and 81% of total P uptake from non-Olsen-P fraction in P0R13 and P0R33 respectively at 95 DAP. However, this amount was lower (70.4%) in P0R0. Furthermore, strain R33 improved P uptake efficiency in sugarcane by changing root morphology (e.g. specific root length and root length) and reducing soil limitations (e.g. enhancement of P compound solubility and P influx).