Agro-Process Intensification through Synthetic Rhizosphere Media for Nitrogen Fixation and Yield Enhancement in Plants

Abstract

Problem statement: In order to combat global warming and the emerging Food, Energy and Water shortages (FEWs), several approaches have been adopted, including genetic engineering and farming practices. Biomass based energy technology will further stress food and water resources and hence novel holistic approaches to FEWs should be designed. Approach: A novel technique (Agro-Process Intensification, A-PI) which simultaneously addresses FEWs in general and food production in particular was described. The technique was based on the enhancement of multiple interactions between plant roots, water, nutrients and bacteria using soil additives in the form of micro-bioreactors which allow plant root growth through them thus generating a micro-environment acting as a Synthetic Rhizo Sphere (SRS). The SRS-media was a nano-structured micro-porous crosslinked, elastic, ionic and highly hydrophilic polymer, facilitating the efficient use of water and nutrients as well as nitrogen fixation in legumes. Results: SRS media, with or without bacteria, was prepared, characterized and used in greenhouse experiments. Grass, for which the enhancement was well above 200% under water stress, was used to evaluate the mechanism of A-PI. The pea plant was used to demonstrate the intensification achievable by biologically active micro-bioreactors in which nitrogen fixing bacteria, Rhizobia, were supported within the SRS-media. Biologically active SRS-media enhanced the plant root infection by nitrogen fixing bacteria and increased both crop yield (ca. 70%) and mineral content. Conclusion/Recommendations: A-PI is achieved principally through the elimination of the random nature of the root/water/nutrient/microorganism interactions. The association of SRS-media with plant roots provides a unique and efficient delivery technique for water and nutrients while protecting beneficial bacteria within the SRS for infection enhancement. Focus on the understanding of the molecular mechanisms of yield enhancement and SRS formation as well as performance in field trials, especially in marginal land under water and nutrient stress, are recommended.