Efficacy of grape seed procyanidins for inhibiting denitrification varies by source, soil texture, and cropping history

Authors: HSIAO, CHE-JEN - University Of Minnesota; FRIE, ALEXANDER - University Of Minnesota; Mitchell, Scott; Venterea, Rodney - Rod; GRIFFIS, TIMOTHY - University Of Minnesota

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2023
Publication Date: 3/1/2024
Citation: Hsiao, C., Frie, A., Mitchell, S.A., Venterea, R.T., Griffis, T. 2024. Efficacy of grape seed procyanidins for inhibiting denitrification varies by source, soil texture, and cropping history. Applied Soil Ecology. 195(March 2024). Article 105254. https://doi.org/10.1016/j.apsoil.2023.105254.
DOI: https://doi.org/10.1016/j.apsoil.2023.105254

Interpretive Summary: Nitrous oxide (N2O) is a potent ozone-depleting and greenhouse gas that is emitted from agricultural soils to the atmosphere following application of nitrogen fertilizers. Microbes in the soil convert the applied fertilizer into N2O via various biological processes including nitrification and denitrification. Soil additives have been developed to slow down nitrification which helps to reduce the amount of N2O that is emitted from the soil. However, additives that inhibit denitrification have yet to be used at the field scale. In this study, we investigated the use of plant-derived compounds (procyanidins) derived from grape seed extract (GSE) as a means of inhibiting denitrification. We conducted a series of laboratory experiments and found that one commercial brand of GSEs inhibited denitrification while another source was ineffective. Two non-procyanidin compounds in commercial GSE mixtures, tartaric acid and gallic acid, actually stimulated denitrification. The inhibition efficiency of the USP GSE varied widely in soils with differing crop histories and physical properties, exhibiting a positive dose-response in three of the five soils examined. Greater effectiveness was observed in sandy compared to silt loam soil and in soil with a history of continuous corn versus soybean production. The timing of GSE application relative to fertilizer addition and one week of storage at room temperature, had smaller effects on denitrification. These findings point out the potential of GSE to reduce N2O emissions but also indicate that further study is needed to better define the conditions under which it will be effective. This study will be of interest to scientists and land managers aiming to reduce the greenhouse gas footprint of agricultural cropping systems.

Technical Abstract: Plant-derived biological denitrification inhibitors (BDI), including procyanidins derived from grape seed extract (GSE), may play an important role in reducing nitrous oxide (N2O) emissions – a greenhouse gas and a stratospheric ozone-depleting substance. However, effects of GSE rate, source, application timing, storage and processing, or soil properties and cropping histories on GSE inhibition of denitrification remain largely unknown. We conducted a series of laboratory microcosm experiments to assess these effects as indicated by denitrification enzyme activity (DEA) with ancillary measurements of N2O and carbon dioxide (CO2) production rates under anaerobic and aerobic conditions, soil inorganic nitrogen (N), and other metrics. Our results revealed that one commercial brand (USP) of GSEs inhibited DEA while another source was ineffective. Two non-procyanidin compounds in commercial GSE mixtures, tartaric acid and gallic acid, actually stimulated DEA. The inhibition efficiency of the USP GSE varied widely in soils with differing crop histories and physical properties, exhibiting a positive dose-response in three of the five soils examined. Greater effectiveness was observed in sandy compared to silt loam soil and in soil with a history of continuous corn versus soybean production. The timing of GSE application relative to urea addition and one week of storage at room temperature, had smaller effects on denitrification inhibition. In corn-cultivated soil, GSE applied with urea reduced cumulative N2O production by 27% compared to soils treated with urea alone. The CO2 production and nitrate levels did not change significantly upon GSE application. Our findings suggest that GSE has the potential as a soil amendment to reduce N2O emissions in corn cultivated soils. However, interactions between procyanidins, soil microbes, and crops may influence GSE denitrification inhibition capacity.