Regulation of Nitrification in Soil: Advances in Integration of \u3cem\u3eBrachiaria\u3c/em\u3e Hybrids to Intensify Agriculture and to Mitigate Climate Change

Higher rates of nitrification in soil facilitate nitrogen (N) losses from agricultural systems through nitrate-leaching and denitrification. Plants’ ability to produce and release nitrification inhibitors from roots and suppress soil-nitrifier activity is termed ‘biological nitrification inhibition’ (BNI) (Subbarao et al., 2015). Up to 70% of applied N-fertilizer is lost (via NO3−leaching and gaseous-N emissions) from agricultural systems and the annual economic loss from lost N-fertilizer is estimated at 90 US$ billion. Previous research has indicated that Brachiaria humidicola (Bh), a tropical forage grass that is well adapted to infertile and waterlogged soils, has high capacity to inhibit nitrification in soil and reduce emissions of a highly potent greenhouse gas, nitrous oxide (N2O) (Subbarao et al., 2009). CIAT has an on-going Brachiaria breeding program that generates interspecific (B. decumbens, B. brizantha, B. ruziziensis) and intraspecific (Bh) hybrids that combine several desirable attributes. An interinstitutional and multidisciplinary project was initiated in 2012 to integrate Brachiaria hybrids into crop-livestock systems of smallholders to improve livestock productivity and mitigate climate change by reducing nitrification in soil (Rao et al., 2014). Here we report the major advances from the last three years of work from this project