So, to continue, how do we "seek balance in our agronomic interventions, and so get more vegetation for our efforts with less N2O,"? How do we persuade Nitrosomonas spp. bacteria - which convert ammoniacal and urea nitrogen fertilizer to nitrite, so that Nitrobacter can convert it to nitrates, which must be done before the denitrification bacteria can convert nitrates to N2O - to back off?

Nitrification inhibitors, such as nitrapyrin, dicyandiamide, and ammonium thiosulfate, slow the conversion of ammonium to nitrate by affecting the soil bacteria.

This blocks denitrification for 2-6 weeks depending on which inhibitor is used as well as soil temperatures. What's more . . .

Nitrogen applied as anhydrous ammonia is all ammonium once it dissolves in the soil water. Anhydrous is toxic to the ammonium-converting bacteria in the injection zone and it takes about 2 weeks for them to repopulate the application zone soil and begin converting ammonium to nitrate.

This doesn't help when nitrogen is already in nitrate form, such as in calcium nitrate, or nitrate in part, such as in urea ammonium nitrate (UAN) or calcium ammonium nitrate (CAN27). Inhibition is not enough, and the inhibitors are not without side effects, such as harming some fishes when applied too heavily. Things that harm or kill bacteria are inherently suspicious in the same way that other pesticides, however benign compared to those of the past, seem suspicious.

Even if all of the bacteria were somehow excluded from a field nitrates could still be lost to leaching and encounter them elsewhere. Denitrification would proceed, and N2O would still be made. How do we reduce leaching?

How deep in the soil profile the nitrate moves depends on the water holding capacity of the soil, how wet the soil is when it begins raining, and the amount of rainfall. A typical sandy soil in Indiana holds about 1-2 inches of rain in each foot of soil. Therefore the movement of nitrate downward is approximately 6 to 12 inches per inch of rainfall if the soil is at field capacity when it begins raining.

If we inhibit denitrification bacteria in soils that have large water holding capacity then we can reduce N2O production, whatever the crop, biofuel or not. We have some methods to do this. Increasing soil organic matter - such as with green or brown manure, compost etc. - and using no-till methods are well known ways to do this. Some minerals such as gypsum help. An emerging method is the use of bio char which not only increases water holding capacity but also retains nitrates through a combination of chemical and mechanical properties until it is released by plants (so to speak, it's complicated, there are microorganisms and enzymes involved).

All of these methods have costs, but nitrogen is getting more expensive too. Precision application of agrochemicals - just enough, at the right place and time - can further reduce the cost of inputs as well as reducing unwanted side effects such as leaching and emissions. The ability to accurately measure soil nutrient levels in real time, on the fly as amendments are applied, would hugely reduce side effects as well as reducing input costs. The technology to do this is still developing, and what there is thus far is expensive, but it's being used in certain places now. Concerns about GHG emissions provide yet another reason to continue development and application of these methods.

IMO our best approach is to improve soil and apply nutrients with precision, rather than inhibiting bacteria. The benefits of ever improving soil - the longer you do it the better the soil gets - go beyond concerns about emissions. And the benefits of precision nutrient application increase as the cost of nutrients rise. This is a happy combination of ancient and modern technologies. It has a sort of charm as well as being exceedingly effective. But, it's not instant karma, you have to work at it and be patient as the tech becomes pervasive. Perhaps the charm of the argument will allow it to compete with political air heads pushing nonsense solutions. One can hope.