Nitrogen in the soil is available to plants in two forms: ammonium (NH4) and nitrate (N03).
The problem with nitrate is, unlike ammonium, it’s a negatively-charged ion that’s not attracted to soil particles or soil organic matter. Nitrate is also water soluble, so it can easily move out of a crop’s rooting zone to places where we don’t want it.
The visual soil column demonstration below, filmed at Ag in Motion, shows how these two forms of nitrogen behave in the soil.
The blue liquid represents the positively-charged ammonium molecule, while the orange liquid represents the negative nitrate molecule, explains Jason Smith, market development specialist for nitrogen stabilizers with Dow AgroSciences.
“The two points I’m hoping people walk away from here with are the stability of nitrogen when we keep it in the ammonium form and how it’s very available for plants to use,” he says.
As part of the nitrification process in the soil, ammonium is naturally oxidized into nitrite by bacteria, often Nitrosomonas spp, and further transformed into nitrate by Nitrobacter spp. As Smith explains, by slowing down the conversion process, a farmer can maintain nitrogen in the more stable, but still plant-available ammonium form for longer.
Check out the video below for a quick explanation of how these forms of nitrogen compare and why it matters: