Managing Nitrogen in Regenerative Systems
March 27, 2023
There is a popular narrative in regenerative agriculture that when we work with nature, we can get all the nitrogen we need for free, because after all, there are 32,000 tons of nitrogen over every acre of land.
And that is true. Except it can also be misleading, as all farmers know who had to learn the hard way.
Getting all our nitrogen for free is something that has to be earned. First, we have to recognize that the 32,000 tons of nitrogen that are available over every acre of land cannot be used directly by plants. Instead, the nitrogen is fixed by either nodules on legumes such as alfalfa and clover, or by soil microbes called nitrogen fixing bacteria. Second, we have to recognize that soil structure plays an important role in how nitrogen is brought into the system and then “fixed”.
As an illustration of how important soil structure is, I heard a story of a grower that has a nitrogen excess on cotton with zero applied-nitrogen. That’s impressive, but what’s even more impressive is how loose and structured his soil is. He can go out into his fields and dig into it with his bare hand, down to his elbow. So imagine a soil that is loose and has good structure down to about 18 inches. Every evening, the earth inhales, and with it goes 18 inches of air that is 78% nitrogen, which is then fixed by nitrogen fixing bacteria. This is how he can get a nitrogen excess without applying any.
So in a situation like this, it is possible to get all your nitrogen from the atmosphere, through soil biology and legumes. The challenge is that, especially in tilled vegetable production, it is very difficult to keep soil structure so good that this can happen. These fields are usually plowed and then tilled in some manner, multiple times. This has the potential to destroy the soil aggregate structure and create soil compaction, which then limits the thickness of the blanket of air that is inhaled every evening, which then limits the amount of nitrogen that is fixed.
My message is this: unless you are doing no-till and have really good, deep structured soil, it is going to be difficult to get all your nitrogen for free. And in vegetable production, you cannot afford the yield drag that you get from nitrogen deficient crops.
So to manage nitrogen in a regenerative system, we want to limit tillage as much as possible, then we can use cover crops that fix nitrogen, we can manage cover crop maturity to maximize nitrogen availability, we can use composts and manure whenever appropriate, and we can also use protein sources of nitrogen such as blood meal, meat meal, soybean meal, feather meal, etc. These sources of nitrogen have a very beneficial effect on soil microbes and also on crops.
We find that when we use these protein forms of nitrogen, we can push the envelope on yield and quality as long as we keep other nutrients in balance as well. Several key nutrients are cobalt and molybdenum, which help metabolize the nitrogen properly and keep the crop internodes short. Additionally, we monitor magnesium and sulfur, which are both critical for protein formation.
In summary, it is possible to get all your nitrogen for free, just remember that you have to earn the right to do so. Also remember that it is much easier to do so in a no-till or limited-till environment. You definitely won’t achieve it in a compacted soil.Source: Melvin Fisher | Sponsored by Keystone Bio-Ag LLC