Improved nitrogen use efficiency in agriculture by CATCH crops as producers of Biological Nitrification Inhibitors

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Agrosystems in industrialized countries are confronted with important challenges: they are facing increasing food demand while they are requested to reduce external inputs and to minimize negative environmental impact. The widespread use of synthetic nitrogen (N) fertilizers has promoted the productivity in agricultural plant production. However, due to the low N use efficiency in crop cultivation, the intensive use of N fertilizers entails losses from the plant-soil system via nitrate leaching and/or N gas emissions, leading to water and atmosphere pollution. Strategies aiming at optimizing N fertilizer management and reducing N losses contribute to several of the UN Strategic Development Goals (SDGs) dealing with global warming (SDG13), responsible production (SDG12), clean water (SDG6) and biodiversity (SDG15). In the CATCH-BNI project, we will investigate the potential of catch crops to provide key functions and services in the regulation of N cycling in conventional and organic agrosystems. The nitrification process operated by soil bacteria and archaea leads to rapid conversion of ammonium into nitrate, which is prone to leaching, and associates with denitrification and the production of greenhouse gases (NOx). While chemical inhibition of nitrification has emerged as a tool to limit nitrate losses, several plant species were lately shown to display nitrification inhibiting activities, mostly through release of Biological Nitrification Inhibitors (BNIs). The use of BNIs allows transferring the nitrification inhibition strategy to organic production systems and represents a low-cost alternative to the application of chemical inhibitors. Tissues from certain catch crop species accumulate compounds with BNI activities, which can be used as green manure to improve soil fertility and reduce the speed of nitrification. This is e.g. the case for glucosinolate-containing plant tissues from some Brassicaceae, for which a greater accumulation of ammonium was observed in soils amended with their tissues. In the CATCH-BNI project we will investigate the incorporation of catch crops with BNI potential into crop rotations as a mitigation strategy to slow down nitrification processes and retain ammonium in soils as well as to increase soil N pools for the subsequent target crop.The main objective of the CATCH-BNI project is to design innovative approaches slowing down the conversion of ammonium to nitrate in soils for optimized nutrition of target crops. For this, we aim at: i) identifying catch crop plant species and/or cultivars with BNI activities in their root exudates and/or root and shoot tissues; ii) understanding how efficiently the N cycle is impacted by the use of BNI-producing catch crops and how the target crops perform (yield and NUE); iii) determining the best options and modalities to stabilize organic fertilizers with BNI plant material and iv) validating in real-field conditions the proposed innovations.