Rhizobium Inoculation Improved the Rhizosphere P Dynamics and P Uptake Capacity of Pigeon Pea Plants Grown in Strongly Weathered Soil Only under P Fertilized Conditions

Abstract

The improvement of phosphorus (P) use efficiency (PUE) is a critical problem in crop production because of phosphorus’ scarcity. Especially in strongly weathered soil with a high P fixation capacity, a low PUE generally limits plant growth. Here, in a 70-day pigeon pea cultivation pot experiment using Ultisols, we evaluated the effects of Rhizobium inoculation (−I/+I) on the plant growth, rhizosphere, bulk soil P dynamics, and plant root P acquisition characteristics, with or without P fertilization (0P: no P application; 50SSP:50 kg P ha−1 with single superphosphate). The combination of Rhizobium inoculation with P fertilization (50SSP + I) increased the plant growth, P uptake, and organic acid content per pot by 63%, 41%, and 130%, respectively, but not without P fertilization (0P + I). The labile and moderately labile inorganic P (NaHCO3-Pi and NaOH-Pi) contents were higher (55% and 44%, respectively) in the rhizosphere soil than those in the bulk soil in the 50SSP + I treatment, indicating the efficient solubilization of the applied P under the 50SSP + I treatment. The fertilized PUE was higher in the 50SSP + I treatment (26%) than that in the 50SSP−I treatment (15%). Thus, these results suggest that Rhizobium inoculation with 50SSP should stimulate plant root P acquisition characteristics, leading to the solubilization of applied P in the rhizosphere and efficient plant P uptake. In conclusion, the 50SSP + I treatment effectively improved the PUE of pigeon peas in strongly weathered soil.

Effect of rhizobium inoculation on rhizosphere phosphorous dynamics and fertilised phosphorous use efficiency in a maize–pigeon pea intercropping system in weathered tropical soil

“…However, it did not increase the fertilised PUE in CS-PP. In contrast, rhizobium inoculation under 0 P did not increase the Pmobilising capacity of PP, soil P availability, or plant P uptake.Consistent with this study,Yamamoto et al (2022) observed that rhizobium inoculation of PP with P fertilisation improved the Pmobilising capacity of organic acids and soil P availability, resulting in a better fertilised PUE Adjei-Nsiah et al (2022). also found that the rhizobium inoculation with P fertilisation in Acrisols was more effective than rhizobium inoculation alone in terms of rhizobial activity (nodule number and weight) and plant growth and highlighted the effectiveness of rhizobium inoculation with P fertilisation in strongly weathered soils.…”

“…Because we conducted the cultivation experiment using nonsterilised T A B L E 4 Summary of the two-way analysis of variance for the effect of rhizobium inoculation (Rhizo) and rhizosphere soil (Soil) on soil P dynamics (Available-P, NaOH-Pi) in NS-I and NS + I under 0P and 50P fertilisation. These results indicate that the inoculated rhizobium strain (B. elkanii USDA61) in this study did not work effectively in the intercropping system, whereas it worked well in PP alone (Yamamoto et al, 2022).…”

“…Rhizobium inoculation treatment was conducted with (+I) or without (–I) rhizobium inoculation. For the +I treatment, we used Bradyrhizobium elkanii USDA61 (USDA) for PPs (Yamamoto et al, 2022). P fertilisation treatments included no P application (0P) and 50 kg P/ha (equivalent to ca.…”

“…Rhizobium inoculation of PPs promoted the secretion of a large amount of organic acids, resulting in a larger available inorganic P (Pi) in the rhizosphere and a higher PUE (Yamamoto et al, 2022).…”

“…Several studies have shown that rhizobium inoculation with P fertilisation improves fertilised PUE, plant growth, and yield parameters in several leguminous crops, including chickpeas and soya beans (Kyei‐Boahen et al, 2017; Ronner et al, 2016; Ulzen et al, 2018). Rhizobium inoculation of PPs promoted the secretion of a large amount of organic acids, resulting in a larger available inorganic P (Pi) in the rhizosphere and a higher PUE (Yamamoto et al, 2022). These results suggest that rhizobium inoculation in legumes enhances their P‐mobilising function, resulting in improved P conditions in the intercropping rhizosphere and, thus, better fertilised PUE.…”