Modern agriculture is sustained by high inputs of nitrogen fertilizer. On the other hand, more than 50% of the nitrogen fertilizer applied to maize and other crops grown in the field is not utilized and this is causing serious problems. Nitrogen fertilizer that is not used by crops is wasted as it flows out of the farmland. Most of this waste is caused by nitrification by soil microorganisms.

Nitrification is a reaction in which nitrifying bacteria in the soil convert the ammonia nitrogen that makes up nitrogen fertilizer into nitrate nitrogen. It is an important process for the earth's nitrogen cycle, but excessive nitrification leads to the production of unnecessary nitric acid, which disturbs the nitrogen cycle. Nitric acid is a negatively charged form of nitrogen that is difficult for field crops to utilize on a continuous basis. This is due to the fact that ammonia, which has a positive charge, is converted to nitric acid, which has a negative charge and cannot be adsorbed because it repels negatively charged soil particles. Nitric acid, which is not adsorbed by soil particles leaks into the ground and contaminates the aquatic environment. Furthermore, nitric acid is converted into nitrous oxide (N₂O), which has a greenhouse effect 298 times greater than CO₂, by denitrifying bacteria in the soil. Therefore, technology to inhibit nitrification will not only improve the nitrogen use efficiency of crops, but also reduce the loss of nitrogen fertilizer and environmental pollution, and improve the global nitrogen cycle.
 

OTAKA Junnosuke: Let's remove excessive fertilizer to build a healthy planet!

JIRCAS is aiming to reduce nitrogen loss from farmland by utilizing the BNI (biological nitrification inhibition) of compounds produced in roots of crops. This time, our research group investigated the BNI compounds in maize roots and discovered four compounds, including one new highly active compound, zeanone. With the identification of these four compounds, JIRCAS will proceed with the construction of a new agricultural system. For more details, please refer to our publication and the press release introducing the paper.

References
Junnosuke Otaka et al. (2021) Biological nitrification inhibition in maize — isolation and identification of hydrophobic inhibitors from root exudates, https://doi.org/10.1007/s00374-021-01577-x

JIRCAS Online Open House 2021: About "nitrification" and "biological nitrification inhibition (BNI)"
https://www.youtube.com/watch?v=nUQR2pVgvWI

Contributor: OTAKA Junnosuke (Biological Resources and Post-harvest Division)