Improve and Sustain Your Crop Farm Land Productivity By Cultivating Nitrogen Fixing Legumes

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Apart from artificial sources (e.g. inorganic nitrogen fertilizers like urea, ammonium sulphate, ammonium nitrate etc) as well as limited natural resources from rain water, the fixation of nitrogen by free living bacteria, supplies the balance of nitrogen needs of the soil.

The best known example of such fixation is demonstrated in the symbiotic relationship between higher plants called “legumes” and a group of bacteria (also called Rhibozium). The symbiotic activity takes place in the root nodules of the plant.

The continuous cultivation of non-legumes (which some farmers are guilty of) depletes soil fertility over time, and this condition is NOT reversible by fertilization of the soil with phosphorous, potassium or trace minerals.

Legume cropping does the opposite of the above. In other words, it does NOT result in depletion of the land’s productivity. Indeed, non-leguminous crops that are planted on land previously cropped with legumes, actually benefit from the nitrogen fixation that would have been substantially facilitated by the growth of the legumes!

It must be noted however, that the nitrogen status of legume cropped soil is ultimately determined to a great extent by the cultural farm practices employed on it.

The following are three possible scenarios:

1. When a crop is ploughed under, full nitrogen gain is realized – meaning a high nitrogen status is achieved.

2. When the cropped legumes are fed to farm animals, the gain is NOT as great as what obtains in 1. above, but it is still quite appreciable.

3. Removal of the above ground portion (known as “stober”) of the crop, in contrast, leads to little improvement in the nitrogen status of the land.

What use can you make of this?

Well, I suggest you consider mixed cropping of non-legumes with leguminous crops like cowpea for instance. Apart from the yield of useful farm crops for sale or in feeding livestock, you will be able to prolong the “life” of your soil – That’s when compared to a situation when you did not crop any legumes.

It is instructive to note that even though they give “quicker” results and are easier to “use”, inorganic or chemical fertilizers tend to leave harmful residues in the soil with attendant side effects. As such, they must be used with proper care and preferably in combination with natural methods like legume cropping.

Also, consider this: if you diligently plant legumes on your land post-harvest of your crops, they would help to replenish the soil before the next planting cycle begins.

The above statement refers to farming situations in which land may be left “idle” after cropped produce has been harvested. In the old days, we were told the “rest” or “fallow” period would allow the land recover. However, in intensive crop farming systems such rest periods may not result in significant nutrient status improvement – except something extra is done.

An example of that something extra would be to deliberately plant legumes on the farmland for the duration of the so called “rest” period, which would then be trimmed/weeded or removed once planting of the main crop (s) is to resume.

Depending on how long the rest period is, and the legume type adopted, a reasonable improvement in nitrogen status of the soil can be expected if this is done.


This article has tried to impress upon the crop farmer, the need to lean more towards natural methods for crop farm land fertility replenishment and sustenance, as against short term benefits of exclusive or major use of chemical fertilizers, which often lead to serious soil damage in the long run.

If you plan to stay in business for the long term, producing profitable crop output from your farm land, it is imperative that you give serious consideration to the use of the strategies described here.


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