L is for ...

If I ask what a Legume is, most people will think about food crop like pulses or groundnuts (Groundnuts are not nuts). The people with a green thumb or a botany inclined will know that I am focused on the plant's ability for nitrogen fixing. I know that not all Legume can fix nitrogen and some non-Legume plants can fix nitrogen but that is a topic for another day.

For those who are not botany inclined, nitrogen fixing is the ability to convert nitrogen in the air to into compounds that the plant can use. That was the science I was taught and it is not totally wrong. However, this gives the wrong impression of what is going on in the soil. The Legume plant does not convert atmospheric nitrogen into nitrogen compound by itself. It first must be infected by certain soil bacteria. The infected plant will develop nodules which then start the nitrogen fixing.

At this point the only beneficiary of the nitrogen fixing is the Legume plant. The soil is still not enriched. This is quite logical since enriching the soil will only encourage competition from other plants. However, Legume are referred as "green manure" so there has to be some hack that man has figured out. The thing is that when the Legume is harvested/uprooted and decomposed, the nitrogen compound in the plant will be returned to the soil allowing future crops to benefit.