High-sorgoleone producing sorghum genetic stocks suppress soil nitrification and NO emissions better than low-sorgoleone producing genetic stocks

Purpose: Rapid nitrification leads to loss of nitrogen (N) fertilizer in agricultural systems. Plant produced/derived biological nitrification inhibitors (BNIs) are an effective eco-strategy to rein-in soil nitrification to improve crop-N uptake and nitrogen use efficiency (NUE) in production systems. Sorgoleone is the major component of hydrophobic-BNI-activity in sorghum roots. However, the role of genetic differences in sorgoleone production in reducing soil nitrification and NO emissions are not established. Methods: Two genetic-stocks of sorghum with high-sorgoleone (HS), and two with low-sorgoleone (LS) production from roots were grown using hydroponics in a plant-growth chamber, in soil in pots in a glasshouse, and in a field experiment. Release of hydrophilic-BNI activity from roots of HS and LS genetic stocks, sorgoleone levels in rhizosphere soils, soil nitrification rates, soil-nitrifier activity and NO emissions were measured to understand the interplay involving sorgoleone release, hydrophilic-BNI release from roots, soil nitrification, plant growth and N uptake. Results: HS-producing genetic-stocks showed higher hydrophilic-BNI-capacity compared to LS- producing genetic-stocks. Biomass production and N uptake were significantly higher in HS than in LS genetic-stocks. Glasshouse and field studies suggest that HS genetic stocks had stronger suppressive impact on soil-nitrifier-populations (ammonia-oxidizing archaea and ammonia-oxidizing bacteria), soil-nitrification, and soil-NO emissions than in LS genetic-stocks. Conclusion: These results demonstrate that HS sorghum genetic-stocks suppress soil nitrifier activity and can potentially reduce N losses from NOleaching and NO emissions more effectively than LS genetic-stocks.