If you read any book on gardening or veg growing, one of the things that the authors bang on about relentlessly is to add compost. Cover the bed with compost, fill the hole with compost, use compost as a mulch and so on. This advice is almost always accompanied by a photo of someone barrowing a huge pile of compost across their (perfect) plot, with a huge smile on their face. What they never tell you is how to create the same copious amounts of compost that they appear to be able to.
The thing about growing veg is that you eat the vast majority of what you grow. If you grow spinach you are left with nothing more than the roots and a few outer leaves, if you grow sprouts you are left with nothing more than a woody stem. Of course, you can rely on the weeds for a bit of green matter, but vast in number though they may be, even they are not enough.
Plot 21 does not have a fine tilth (yet). I am pleased with golf-ball sizes of soil but orange size is more usual here.
No sign of a tilth here
I have in the past paid to have manure delivered to the allotment, but now that I have two plots, I can't afford this (at least, I can afford to have the same amount delivered as before, but the quantity won't make much of an impact on all the space we have). We also sometimes go and bag up manure ourselves but still we can never get enough. At the moment I am reluctant to get any at all as it will all be so full of water.
So starting last year I have been trying out green manures. I grew Phacelia, Buckwheat and mustard quite successfully. I had mixed results with Crimson Clover and the Rye and Tares failed completely.
Buckwheat was the first to go in, once the soil had warmed up. It germinated well but didn't get very tall before it started flowering, the result I think of having a clay soil that dried out very quickly after a few warm days. The Phacelia also germinated well and gave a good covering. I had read that you should not leave green manures to flower as if you do, the stems go woody. And it is true. You lose much of the lush green growth you have created. I struggled the most with this problem with the Phacelia which was alive with bees when it was in flower. Every time I went up to the allotment to cut it down, I would end up just sitting and watching the bees! Not so this year, I'm going to toughen up and cut it all down at the first sign of a flower... but maybe leave a bit around the edges of the beds for the insects.
Both Buckwheat and Phacelia are easy to grow and easy to pull out by hand if they start self-seeding everywhere. They add organic matter to the soil but I don't think they offer huge benefits. Crimson Clover meanwhile adds nitrogen to the soil. I have over-wintered CC on two beds this year and it has been great for stopping a pan forming on the soil surface, so I will grow it again next year. Rye and Tares should have the same effect but mine didn't take off at all. I'm not sure if it didn't germinate or if it did and the pigeons ate the seedlings. I shall have to try again later this year and see what happens.
I have bought a packet of Lupin seeds as they make good green manure. The tap roots are good are breaking up the soil and they also fix nitrogen. But can i really be expected to cut down a bed of lupins before they flower......