Targeted Phosphorus Fertilization in the Peanut Pod Zone Modulates Pod Nutrient Allocation and Reshapes the Geocarposphere Microbial Community

Excessive fertilization often causes soil acidification, adversely affecting crop growth and yield. While calcium uptake by peanut pods is documented, the absorption of other nutrients remains less explored. This study investigated the effects of localized phosphorus (P) fertilizer application solely to the pod zone on pod quality, yield, and the microbial community (phosphorus-solubilizing bacteria, PSB, and nitrogen-fixing bacteria, NFB) in the geocarposphere, with the root zone isolated and left unfertilized. Results demonstrated that pod-zone P application significantly increased the nitrogen and phosphorus content in kernels. Microbiome analysis revealed that this targeted fertilization altered the diversity, abundance, and dominant species of PSB. In contrast, while the abundance of NFB increased, their species diversity and dominant flora remained unchanged. These findings indicate that precise P fertilization to the pod zone enhances peanut quality and modifies the geocarposphere microbiome structure. This study highlights the significant nutrient absorption capacity of pods themselves and its role in plant development. It also suggests that rational, localized fertilization strategies can improve yield and quality by optimizing nutrient uptake and influencing the rhizosphere microbiome, offering a potential approach to mitigate the negative impacts of conventional fertilization practices.