Green manure

It does not come from Martian horses or cows. The explanatory section below has been taken from a Henry Doubleday Research Association (HDRA) factsheet.

Green manures are plants that are sown specifically to improve fertility. They are not harvested for food, and are not allowed to flower. Any plant can be grown as a green manure although some are much better than others and are available as seed especially for the purpose.

There are all sorts of good reasons for growing green manures. They will... 

• Improve soil fertility - clover and other legumes harvest nitrogen from the air. 

• Keep soil fertility - mop up plant foods on empty land, so they are not washed out by the rain. 

• Protect soil structure - a 'cover crop' protects the soil from damage by heavy rain. 

• Keep down weeds - smother seedlings and compete for light and plant foods. 

• Help control pests - provide safe cover for beetles, frogs and other predators. 

• Stimulate soil biological activity - microbes and other soil organisms rapidly colonise green manure foliage dug into the soil. Increased biological activity makes for a more productive soil. 

• Loosen the soil - deep rooting green manures can help to loosen and aerate the soil deep into the ground. 

• Protect soil life - a living mulch protects creatures in the soil from the extremes of weather.

The photograph shows how well green manure can grow if planted at the right time. The seeds were sown after the early potato crop had been lifted. A later sowing elsewhere during dry weather has not done so well despite some watering.

On Friday 14th January BBC Gardeners Question Time had a short bit about the benefits of green manure although Bob Flowerdew had reservations because he reckoned some weeds would do almost as well. 

Anyone interested the potential of green manure can read the whole factsheet by clicking here.