“Beans, Beans, they’re good for your field,
The more you plant, the more you’ll yield.
The more you yield, the less you’ll owe,
So beans, beans, for every row.”
When I visited the farm of Carlos Sergio Sanglard, I noticed the peanuts planted around the coffee trees. (He also grows organic beans). At Luis Adauto’s farm he grabbed the soil, showed me the worms, and then expounded on what we couldn’t see. Here is a slice of what he was talking about.
N2 – Bacteria
Although 80% of the atmosphere is nitrogen, and nitrogen is essential for plants and animals, the nitrogen (N2) in the atmosphere must first be converted to ammonia, nitrates, and nitrogen dioxide to be used. This is as true for humans as it is for coffee plants. Bacteria perform this essential task. While there are bacteria present in the atmosphere and soil that perform this conversion, their production is not sufficient for raising crops.
Rhizobium, Nodules, and Nitrogenase
Root nodules are formed when the soil bacteria Rhizobium enters the roots of the plant and multiplies within the cortex cells. These nodules then produce nitrogenase, bacterial enzymes that convert the N2 to ammonia and nitrates. Almost all of this “usable” nitrogen is stored in the plant and is not released until the plant or parts of it die. Rhizobia by themselves cannot fix nitrogen.
Which Plants Convert and Release the Most Nitrogen?
Beans will generally have less than 100 nodules per plant, soybeans will have several hundred per plant and peanuts may have 1,000 or more nodules on a well-developed plant. A peanut plant can produce up to 250lbs of nitrogen per acre. Alfalfa and clover may produce up to 500. (Source “Nitrogen Fixation by Legumes, ” New Mexico State University Cooperative Extension Service).
If you follow the far left side down, and third column up (nitrates to assimilation), you can see how nitrogen is taken from the air and makes its way into coffee.
Here is a photo of Sergio standing in some of the undergrowth between rows that is planted for nitrogen fixation