Hi, I found these instructions on an American website.



September

The first step toward high tomato yields is taken in early September when you prepare permanent raised tomato beds. If you're trying this method for the first time, use an inoculum to establish the proper soil bacteria.
Seed the beds with hairy vetch, a winter-hardy legume that's becoming widely available. Do this about 2 months before winter freezeup. Seedlings will emerge within 1 week. By the time that frost arrives, plants will be 5 to 6 inches tall.
Above ground, these skinny little vines will form a mat. Underground, the root systems will all this time be growing into an extensive network. Foliage and root systems will be working together, above and below ground, to hold the soil firmly and stop erosion.
Below-freezing weather will cause the vetch vines to become dormant, but never fear—Spring reinvigorates growth.
Now that wasn't too tough. And the good news is, you won't have to do anything else until May.

May

By May, individual vines will be 4 or 5 feet long and form thick stands about 2 feet high. Now it's time to kill them.
Yes, I said kill them!
Determine your ideal tomato-planting time. The day before, go out and buy however many tomato seedlings you're prepared to cultivate.
Then mow the vetch (a high-speed flail mower is recommended) and leave the residue in place on the beds. For the next several months, the dead vines are going to form a nutritious organic blanket that will snuggle up to your tomato plants (keeping out weeds) and gradually break down into soil nutrients.
Tomorrow you'll transplant young tomato plants right through the mulch residue and into the underlying soil.
Moisture is vital, so you'll need to irrigate. Immediately after planting, install trickle irrigation lines on top of the vetch and 3 to 4 inches from the tomato row. Fix them in place with U-shaped wires.
Fertilizers? A good stand of vetch provides sufficient nitrogen to meet from half to all the nitrogen needed by tomatoes. As for phosphorus, potassium, and essential micronutrients, it's best to have your soil tested—and supplement according to the soil's specific needs.

June…and Beyond

During the first month after mowing, expect the vetch mulch to suppress weed emergence. After that, as the decomposition of the residue advances, weed seedlings are likely to emerge.
One herbicidal application of 0.5 pound active ingredient of metribuzin per acre should do the trick, applied 3 to 4 weeks after transplanting. (Your nursery professional can help compute the quantity needed for small applications.) This application will also kill any regrowth from the mowed vetch plants.
By summer's end, your tomato plants will bear an abundance of fruit, the organic mulch will decompose to a fare-thee-well, and the year will have come full circle.
Mow the old tomato plants and leave them in the field to decompose like the vetch mulch.

Now it's time to reseed with... hairy vetch!


Has anyone tried it?

Does it work in the greenhouse as well as outdoors?

Where do you get Hairy Vetch ib the UK?

Would this cause a problem with Blight spore buildup?

I would appreciate any comments

Vivie

There is research ongoing on the benefits of a hairy vetch cover crop fror
tomatoes. Traditionally hairy vetch has been used in combination with rye as a
winter cover crop (green manure). One study just summarized in The American
Vegetable Grower is by Abdul- Baki a t the USDA Sustainable Agricultural
Systems Laboratory at Beltsville Maryland. Note that the comparisons are with
plastic mulch and on irrigated crops and for areas without crop rotation. There
is no question that green manures work and that sod planting is viable. Whether
hairy vetch is superior to other legumes like clover or even other winter cover
crops is still open to debate.

There is research ongoing on the benefits of a hairy vetch cover crop fror
tomatoes. Traditionally hairy vetch has been used in combination with rye as a
winter cover crop (green manure). One study just summarized in The American
Vegetable Grower is by Abdul- Baki a t the USDA Sustainable Agricultural
Systems Laboratory at Beltsville Maryland. Note that the comparisons are with
plastic mulch and on irrigated crops and for areas without crop rotation. There
is no question that green manures work and that sod planting is viable. Whether
hairy vetch is superior to other legumes like clover or even other winter cover
crops is still open to debate.