Effect of Phenolic Acid Allelochemicals on Nutrient Supply Capacity of Rhizosphere Soil

In order to explore how allelochemicals limit the nutrient absorption of recipient plants, this study analyzed the effects of different concentrations of 4-Hydroxybenzoic acid (p-HA) and cinnamic acid (CA) (used as allelochemicals) on soil enzyme activities and microbial properties related to carbon (C), nitrogen (N) and phosphorus (P) cycles in the rhizosphere soil of lettuce and tomato (used as recipient plants) in a pot experiment. The results show that the higher concentrations of p-HA and CA, the higher inhibiting effects on nutrient absorption of leaf. With the increase of allelopathic stress, the contents of microbial biomass C, N and P and the activities of sucrase, amylase, urease, protease and phosphatase in the rhizosphere soil of recipient plants were decreased. These experimental results partly reveal two important ways of phenolic acid allelochemicals limit the nutrient uptake by recipient plants and inhibiting their growth, which are associated with the decrease in the contents of microbial biomass C, N, and P, and the enzyme activities related to the cycling of C, N, and P elements in the rhizosphere soil of recipient plant.