School of BioSciences - Research Publications
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ItemNo Preview AvailableDeciphering the Interactions in the Root-Soil Nexus Caused by Urease and Nitrification Inhibitors: A Review(MDPI, 2023-06)Optimizing nitrogen (N) availability to plants is crucial for achieving maximum crop yield and quality. However, ensuring the appropriate supply of N to crops is challenging due to the various pathways through which N can be lost, such as ammonia (NH3) volatilization, nitrous oxide emissions, denitrification, nitrate (NO3−) leaching, and runoff. Additionally, N can become immobilized by soil minerals when ammonium (NH4+) gets trapped in the interlayers of clay minerals. Although synchronizing N availability with plant uptake could potentially reduce N loss, this approach is hindered by the fact that N loss from crop fields is typically influenced by a combination of management practices (which can be controlled) and weather dynamics, particularly precipitation, temperature fluctuations, and wind (which are beyond our control). In recent years, the use of urease and nitrification inhibitors has emerged as a strategy to temporarily delay the microbiological transformations of N-based fertilizers, thereby synchronizing N availability with plant uptake and mitigating N loss. Urease inhibitors slow down the hydrolysis of urea to NH4+ and reduce nitrogen loss through NH3 volatilization. Nitrification inhibitors temporarily inhibit soil bacteria (Nitrosomonas spp.) that convert NH4+ to nitrite (NO2−), thereby slowing down the first and rate-determining step of the nitrification process and reducing nitrogen loss as NO3− or through denitrification. This review aims to provide a comprehensive understanding of urease and nitrification inhibitor technologies and their profound implications for plants and root nitrogen uptake. It underscores the critical need to develop design principles for inhibitors with enhanced efficiency, highlighting their potential to revolutionize agricultural practices. Furthermore, this review offers valuable insights into future directions for inhibitor usage and emphasizes the essential traits that superior inhibitors should possess, thereby paving the way for innovative advancements in optimizing nitrogen management and ensuring sustainable crop production.
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ItemAssessing the Efficacy, Acute Toxicity, and Binding Modes of the Agricultural Nitrification Inhibitors 3,4-Dimethyl-1H-pyrazole (DMP) and Dicyandiamide (DCD) with Nitrosomonas europaea(American Chemical Society, 2023-01-25)Nitrification inhibitors have been coformulated with nitrogen fertilizers since the 1970s to modulate the microbiological conversion of nitrogen in agricultural soils. 3,4-Dimethyl-1H-pyrazole (DMP) and dicyandiamide (DCD) are currently the most used commercial nitrification inhibitors, but their mode of action is not well understood. This work seeks to fill this void by assessing for the first time in detail their mechanism of inhibition, efficacy, and acute toxicity with pure cell cultures of Nitrosomonas europaea. Bacterial assays based on the quantification of the nitrite (NO2–) production showed that both inhibitors reversibly target ammonia monooxygenase (AMO), which catalyzes the first step of the nitrification process. Michaelis–Menten kinetics suggest that both DMP and DCD act as uncompetitive inhibitors. Real-time measurements of the oxygen (O2) consumption confirmed the nonmechanistic mode of inhibition and showed that DMP reduced the O2 uptake rate by AMO much more at considerably lower concentrations than DCD, in line with the lower inhibitory efficiency of the latter. Acute toxicity tests revealed that DCD has a 10% higher toxicity than DMP when comparing treatments at the same inhibition efficacy (i.e., DMP at 10 ppm, DCD at 100 ppm), indicating that the inhibition of the nitrification process cannot simply be achieved by increasing the inhibitor concentration. The methods presented in this study could assist the development of more reliable nitrification inhibitors in the future.
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ItemNo Preview AvailableRapid and Inexpensive Assay for Testing the Efficiency of Potential New Synthetic Nitrification Inhibitors(AMER CHEMICAL SOC, 2023-03-20)