Nitrogen is one of the most important food sources for our plants. Plants are built to draw nitrogen from the soil/water where it exists in several forms – some available for plants to use and others not. But floating above their oblivious green heads there’s an entire world of nitrogen. About 90% of the earth’s nitrogen exists in the atmosphere and not in the soil. In fact the atmosphere is just about 79% nitrogen, 21% oxygen, and eleventy billion percent filth.
Nitrogen in the soil comes from a few nicely evolved systems. Most comes from a slightly freaky-sci-fi-slightly-symbiotic force called fixation. In fixation, several species of bacteria can absorb atmospheric dinotrogen gas which they then convert into ammonium. Ammonium is structurally NH4 and in this form, plants can (and happily do) grab the nitrogen bit.
Happy bacteria and stuff do a few other things in the soil to produce or make use of nitrogen via nitrification and mineralization. Mineralization happens when stuff breaks down in the soil and the organisms turn that nitrogen into ammonium and nitrification is sort of the reverse process.
The cool thing is that all of these happy little bacteria guys sit around in the soil with specialized jobs. Many plants require the nitrogen to be absorbed via water, but legumes like peas and beans have a deal with the bacteria. They let the bacteria live in nodules within their root structure, they provide the bacteria with the fuel to fix nitrogen right from the air and in turn the legumes draw on the nitrogen. It’s a contained fertilizing system! (Incidentally, reproducing this system in a factory requires tons of energy… it’s why making fertilizer blows.)
So, if the system occurs naturally why are we told to use inoculant on our legumes? And is the inoculant “natural”? It sounds sinister.
Inoculant is usually a powdery substance and it’s nothing more than a grouping of a specific type of nitrogen-fixing bacteria. Each kind of legume will require a certain type of bacteria. For peas it’s usually R. leguminosarium. Beans need R. Phaseoli. Lasagna needs Chef Boyardeeoli. These bacteria are natural. I have seen or heard of some kinds of peas and beans that are pre-treated with inoculant and that sounds a little unnatural to me. It’s a bit like seeds that are pre-treated with chemicals to resist rotting or freezing or being good for you.
Using an inoculant that is right for your crop is a good idea. It’s not a mandatory, but it helps ensure that your plants will be boosted along with the right bacteria. These buggies exist in the soil, but sometimes not where you are planting or perhaps not in a big enough way. Using it is easy. You can make a slurry out of the powder by adding some water, drop your seeds in, coat them and plant them within 24 hours. If you’re curious, you’ll know it worked later by taking a look at the roots. If they’ve got gnarly looking white nodules, that’s your little nitrogen factories hard at work!
Incidentally, if you’re using an inoculant, don’t add your own nitrogen fertilzer to your plants. Peas and beans, like me, are gorgeous, productive and truly, truly lazy. If you give them an easy buffet of food, they won’t work to create their own.