Screening Potential Nitrification Inhibitors through a Structure–Activity Relationship Study—The Case of Cinnamic Acid Derivatives

Abstract

Using a nitrification inhibitor to decrease nitrification rates in soil represents a promising strategy to improve nitrogen fertilizer use efficiency. Nonetheless, rapid screening of nitrification inhibitors remains challenging. In this study, we propose a strategy to screen potential nitrification inhibitors through a structure–activity relationship (SAR) study based on a rapid determination of nitrification inhibition. To demonstrate this, the nitrification inhibition potentials of cinnamic acid derivatives against Nitrosomonas europaea growth were evaluated in a liquid culture. The SAR study showed that hydroxyl and fluoride groups were the favorable substituents on the benzene ring, and the ester group and double bond in the side chain were essential for maintaining high inhibition efficacy. Three compounds with notable inhibitory efficacy (EC50 = 8–25 μM) were further assessed in agricultural soil, and they displayed a noteworthy reduction in nitrification rate and bacterial amoA gene numbers. Based on the results, we identified methyl cinnamate, methyl 4-hydroxycinnamate, and methyl 4-fluorocinnamate as promising candidates for nitrification inhibition.