IMPROVING CARBON- AND NITROGEN CYCLE LINKAGES IN AGRICULTURAL SOIL MICROBIOMES FOR ENHANCED CARBON STORAGE AND CROP NITROGEN USE EFFICIENCY

This project will functionally characterize microbial carbon- and nitrogen-cycling processes and their linkages to plant nutrition, nitrification, and nitrogen loss via a combination of soil chemical and microbial activity measurements with metatranscriptomic analyses of gene expression activity and targeted manipulation experiments to test the impact of nitrification and agricultural management on soil carbon- and nitrogen cycling and long-term trends in soil carbon stocks.The project will generate significant novel mechanistic insight into carbon- and nitrogen cycling in tropical agricultural soils with contrasting soil properties and management. It will identify keystone microbial species and metabolic pathways with a potential to transform agricultural best management practices though microbiome-informed sustainable practices for production and regenerative agriculture. The project will also contribute to training the next generation of soil scientists at the undergraduate, graduate, and postgraduate levels.Specific Objectives: 1) Functionally characterize linked carbon- and nitrogen cycling activity in organic and sandy agricultural soils over two seasonal cycles. 2) Characterize carbon- and nitrogen cycling microbiome functions in organic and sandy soils by metagenomic and metatranscriptomic analysis.3) Identify effects of nitrification inhibitors and agricultural management on carbon- and nitrogen cycle microbial interactions in targeted manipulation experiments.To achieve the overarching goal of developing strategies that improve carbon- and nitrogen cycle linkages in agricultural soil microbiomes for enhanced carbon storage and crop nitrogen use efficiency, we will use a polyphasic approach combining (1) a two-year time series of soil chemistry, as well as microbial carbon and nitrogen cycling activities in two contrasting soil types (organic vs. sandy soils) under cropped and fallow conditions; (2) molecular characterization of microbial community structure and functional gene expression patterns in soil microbiomes; and (3) microcosm- and soil lysimeter-based manipulation experiments using nitrification inhibitors and flooded rice cultivation. Together these approaches will provide a comprehensive assessment of microbial carbon- and nutrient cycling in contrasting agricultural soils. The data will be integrated into a comprehensive seasonal carbon- and nitrogen cycling model for organic and sandy soils.