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

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.

Automated summary

In strongly weathered soil, the combination of Rhizobium inoculation and 50SSP (single superphosphate) fertilization effectively improves phosphorus use efficiency in pigeon peas.