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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. [ABSTRACT FROM AUTHOR]

Intercropping with cereal and phosphorus (P)-mobilizing leguminous crops is a traditional agricultural practice in Sub-Saharan Africa. It is essential to evaluate the effect of intercropping (i.e., rhizosphere sharing) on fractionated rhizosphere soil P dynamics under the various soil P conditions and legumes, to improve the soil-plant P dynamics in this region. This study aimed to identify the effect of rhizosphere sharing of maize (MZ)/P-mobilizing legumes intercropping on fractionated rhizosphere soil P dynamics and plant P uptake under different P fertilization rates in strongly weathered cropland soil of Tanzania. We conducted 60-day MZ and P-mobilizing legumes intercropping pot experiments under different P-fertilized conditions (0, 50, and 100 kg P ha−1) with two legumes (pigeon pea (PP) and groundnut (GN)) by using three different root-separation treatments (no separation (NS) for rhizosphere sharing, nylon mesh separation (MS), and complete separation (CS)), to compare the effect of rhizosphere sharing in one pot. We evaluated the Hedley-fractionated P of rhizosphere soil and plant P uptake in each pot. We found that both P-efficient legumes did not clearly decrease the less labile P (NaOH-P) of rhizosphere soil in no P treatment, while these clearly decreased the less labile P in 100 kg P ha−1 treatment. It indicates that P-efficient legumes can solubilize the fertilized P but not native less labile P of the soil. The NS treatment increased the labile P of rhizosphere compared with CS by solubilizing the fertilized P, except for MZ/GN intercropping at 50 kg P ha−1. Relative to CS, MZ/PP intercropping increased the total plant P uptake per pot (20%–40%) under P-fertilized conditions, whereas MZ/GN intercropping decreased it (17%) at 50 kg P ha−1 or showed no change at 100 kg P ha−1. MZ/PP intercropping improved P fertilizer recovery efficiency, whereas MZ/GN intercropping did not. Enhanced P use efficiency through intercropping with P-mobilizing legumes is dependent on P-solubilizing characteristics of each P-mobilizing legume. [ABSTRACT FROM AUTHOR]