Root-driven phosphorus mobilization in Chinese cabbage: Rhizosphere adaptations and impacts on soil phosphorus...

Improving the capacity of vegetable roots to phosphorus (P) uptake is crucial to ensure high yield and P utilization efficiency. However, it remains unclear how the changes in roots and rhizosphere characteristics under varying P fertilizer application affect soil P transformation and uptake by roots. Field experiments were conducted for two consecutive years with five different P application rates (0, 33, 65, 131, and 393 kg P ha^-1) to explore strategies for improving P uptake in Chinese cabbage. The findings indicated that the yield of Chinese cabbage significant positive linear increased with P fertilization. P fertilizer application resulted in an increasing concentration and uptake of total P, as well as root length and surface area in the Chinese cabbage. Inversely, the average P absorption efficiency decreased from 43.8 % at 33 kg ha^-1 level to 8.5 % at 393 kg ha^-1 level. Additionally, the exudation of oxalate, succinate, citrate, and malate significantly decreased with increasing P fertilizer application, whereas no significant changes were observed for lactate. P fertilizer significantly increased soil Olsen-P and the concentration of different P fractions, except for NaHCO₃-P_o and NaOH-P_i. Under P deficiency, root oxalate exudation-driven dissolution of secondary mineral P (NaOH-Pi) was enhanced by rhizosphere soil P depletion. Furthermore, a significant positive relationship was observed between ΔOlsen-P, Δsparingly labile P, Δnon-labile P, and carboxylates exudation. Based on the critical soil available P threshold of 20.64 mg kg^-1 (Olsen-P) for 91 % relative yield. Balanced P supply promotes root oxalate exudation in Chinese cabbage, liberating NaOH-Pi into bioavailable NaHCO3-Po that sustains rhizosphere P homeostasis.