Nitrogen Stabilizers: DMPP or DCD

Nitrogen stabilizers are pretty good at reducing N₂O emissions; there's a molecule doing the tough work and it's usually one of two: DMPP or DCD. We explore the differences below.

What they're actually doing

Both are nitrification inhibitors. That means they slow down the microbial conversion of ammonium (NH₄⁺) into nitrate (NO₃⁻) in soil. Specifically, they block ammonia monooxygenase, the enzyme Nitrosomonas bacteria use to kick off that conversion.

Nitrification, and the denitrification that follows are where most agricultural N₂O comes from. N₂O is roughly 273 times more potent than CO₂ over a 100 year horizon, so keeping nitrogen in ammonium form for longer is beneficial for a crops’ slow intake and the environment.

DCD

Dicyandiamide is the longer-established of the two. It is inexpensive, highly water-soluble, and widely available, which is why it has seen extensive use in pasture systems. That solubility is also its main constraint. DCD is mobile in soil, raising the risk of it moving away from the ammonium it is meant to protect, and raising residue concerns.

It also requires a relatively high dose, so it is typically blended into fertiliser, dissolved in slurry or effluent, or spray-applied to pasture rather than coated onto granules.

DMPP

3,4-dimethylpyrazole phosphate acts on the same enzyme but at roughly one-tenth the dose, around 1% of applied nitrogen. That low rate makes it practical to incorporate directly into compound fertilisers. It is also less mobile and less volatile than DCD, remaining closer to the point of application.

How they compare

Both act on the same enzyme through the same mechanism. Both are transient, lasting weeks to months, and both degrade faster as soils warm, so neither offers season-long protection in hot conditions.