Rhizosphere response and resistance to fertilization

Investigating the response of the rhizosphere and bulk soil to fertilization, along with the mechanisms governing their dynamic and stability, is essential to understand root and microbial functions in ecosystems. Here we synthesized 7606 pairwise observations based on 3803 paired samples from rhizosphere and bulk soil to assess how chemical and microbiological properties respond to application of mineral and organic fertilizers across croplands, grasslands, and forests. Fertilization positively altered the overall chemical properties of rhizosphere and bulk soil by 21% and 18%, respectively, while microbiological properties remained largely unchanged except for microbial biomass and the activities of certain enzymes. Fertilization decreased the response variability of soil properties, resulting in reduced heterogeneity, particularly in bulk soil. The response slopes of rhizosphere and bulk soil properties to fertilization were below 1.0, indicating that the rhizosphere had greater resistance, especially under organo-mineral fertilizer application. This high resistance stems from i) large input or available compounds by roots maintaining the stability of microbial communities in rhizosphere, ii) stronger microbial control over chemical properties, and iii) a larger gap in response variability between rhizosphere and bulk soil. In conclusion, while rhizosphere and bulk soil properties respond similarly to fertilization, the rhizosphere demonstrates greater stability due to its higher resistance. The rhizosphere showed greater resistance to fertilization than bulk soil owing to stronger microbial effects on chemical properties and a marked difference in response variability, based on a global meta-analysis of 7606 observations across farmlands, grasslands, and forests.