Saturday, June 8, 2013

Green Manure - Nature's Industrial Chemistry

Discovering green manure was for me one of the intriguing gardening practices.  I have always been fascinated by the ability of natural organisms to undertake chemical synthesis, sometimes complex, sometimes very simple and manufacture their own materials. While this may sound like stating the obvious, the fact is that I love chemistry, and I love gardening, and I say these things sometimes. The idea that you could give something back to the soil by growing something in it sounds so counter-intuitive but turns out to be a cheap and efficient source of soil nutrition. The key process, (well, one of them) is this ability that plants have to 'fix' Nitrogen from the atmosphere, processing it into a form that the plant can use for food. To get all technical for a minute, the gaseous atmospheric Nitrogen molecules N(2) are rearranged by enzymes called nitrogenase to form ammonia NH(3). Without this tiny, simple chemical equation, none of us would be here to do yoga, knitting or motorcross, can you imagine? Copying this remarkable feat of natural chemistry had to wait for the twentieth century and a guy called Fritz Harber, the less said about him the better really. He developed a simple industrial technique for fixing atmopheric Nitrogen that has become the backbone of fertilizer industry, the explosives industry and in a bizzare company merger, the exploding fertilizer factory industry! Anyway while it is a triumph of man poking his tounge out at nature, fertilizing crops with anhydrous ammonia in a big tank is about as far from nature's way as you could get and the runoff from this practice causes serious ecological problems. Long story short, anything we can give back to the soil without the help of Mr Harber the better and green manure is the perfect way to do it.

This is the third time I have grown a green manure crop in the long front bed. The first time I tried oats and woolly pod vetch, which didn't turn out to be 'woolly' as I'd hoped. The second go was a massive crop of broad beans, they blocked out the sun. The only problem there was, it turns out, a lot of people really like to eat broad beans and if you grow them where they can see, they won't take kindly to you cutting them down before the beans form and forking them into the ground. Seriously they look at you like you're insane and then say things to you like, "We'll maybe I'll just fork my next cake back into the flour bag and not bring you a slice." There are two solutions to this problem. 1. Grow a second (smaller) supply of broad beans and assure your neighbors that they'll get to sample their old world 'greeny' taste in good time. 2. Greater green manure awareness. This year I'm growing broad beans again including of course, a supplementary crop for consumption. I bought a kilogram of seeds which turns out to be a LOT of seeds and have treated the seeds for the green manure bed with the special powdery black inoculate. This I am told, supplies Nitrogen fixing bacteria to the roots of legumes like broad beans. When the plants are just about to flower, I will take to them with implements and send them soil-ward. Until then it's feet up while nature, the industrial chemist goes to work, campaign for green manure awareness and an end to fertilizer factory explosions please!

Just remember Ruby Rhod says, "it MUST be green, m-kay, m-kay!?"
We shall be needing oxygen masks when we get to the top of that one won't we Sir Edmund!
A field of little atmospheric processing units.

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