Nitrogen Balances

Grain farmers use nitrogen balances to see how much chemical fertilizer they need to get commercial yields of their crop. I worked as a farm supply manager at a large grain elevator and learned about nitrogen balances selling fertilizer to these big growers.

Organic nitrogen balances can help farmers balance crop nitrogen needs with available nitrogen from the soil and any applied materials. Three nitrogen balance questions must be answered:

How much nitrogen does your crop need?
How much nitrogen does your soil release?
Where does the rest of the available nitrogen come from?

Nitrogen balances help target yields but also are useful for building up organic matter levels. Can nitrogen balances help with pest management and rotation planning as well? Yes, it looks like they can but more on that at another time.

Conventional farmers were correct to focus on available nitrogen since the levels of this essential nutrient are key drivers of several biological processes. The criticism of organic is always low yields. I now believe this is a matter of inefficient organic nitrogen management. Research shows biological processes can produce good yields without the need for fertilizer each year.

Nitrogen is also critical for the growth of the soil microbes as they build tissues with it (proteins are nitrogen based). Plants take carbon from the air. The microbes can store this carbon for the long term as humus BUT enough available nitrogen has to be present to form this stable organic matter.

Soil organic matter has a carbon to nitrogen ratio (C/N) of around 12. That means each unit of organic matter is made up of 12 parts carbon and 1 part nitrogen. This nitrogen is tied up with the carbon and is not available for microbes or crops to use. Farmers think about needing nitrogen for crop yields but do not often consider that nitrogen is also needed to build organic matter.

Organic nitrogen balances involve calculations for availability and carry over the next year. Chemical fertilizers do not carry over but leach out in the fall. Organic vegetable growers can use nitrogen balances to manage nutrients organically. This is a key factor in planning crop rotations, managing pests and capturing carbon to build healthy soils.

Crops fall into three broad nitrogen needs groups. This will be discussed in detail in future blogs. Paid members can join discussions about organic nitrogen management in our farmer forums.

Today, we just touched the highlights around nitrogen balances as the key to organic nutrient management. Are nitrogen balances also central to crop rotation planing and pest management ? Future Blog posts will discuss what research says about these key areas of food production.