Green Manures & Can You Sow Them Now?

As it has been wet and miserable most of this week, I haven’t been to my allotment much and I thought I would take this chance to talk about ‘Green Manures‘ as they are still something of a mystery to lots of people.

My wet and windy back garden this week

My wet and windy back garden this week

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So what is a green manure and why is it good to use it?…….

A green manure is a plant that is grown to benefit the soil.  Farmers have used green manures for centuries to improve soils.  It improves the fertility and soil structure. It helps to open up heavy soils and improve drainage and in light soils the green manure acts like a sponge and stops the moisture from draining away.

Green manures can also be used to help stop the nutrients from washing out of the soil in heavy rain, as they hold on to the nutrients through their roots.  Some green manures fix nitrogen in the soil as well, ready for the next crop you plant.

Green manures are usually used on bare patches of soil that are not going to be used for a while, but it can also be used between widely spaced plants, e.g. sweetcorn, to stop weed growth.

Green manures are good for predators that control pests, as they are a welcome habitat for them.  Frogs and beetles enjoy the damp, cool ground underneath it.

Some flying pests can be confused by green manures.  If you let it flower near to your crops e.g. under planting brassica’s with ‘trefoil’, is said to deter cabbage root fly.

When you dig in green manures, it stimulates the activity of microscopic creatures that consume the decomposing foliage, which helps to have a healthy soil, which is good for the plants.

One thing that needs to be taken into consideration, is that as a green manure foliage decomposes, it releases compounds that can inhibit the germination of small seeds, so it’s best to leave it for a while  before sowing.  This does have it’s good side, as it also inhibits weed seeds too.

Phacelia tanacetifolia

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So can I plant a green manure now?

Yes, it’s not too late to plant a couple of them here in the UK:

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Field Beans (Vicia faba)

Field Beans are in the Leguminosae  family (Peas and Beans).  They can be planted between September and November and they will grow overwinter.

Field Beans prefer heavy soils e.g. clay and they fix nitrogen in the soil which will benefit following crops.

The beans need to be sown at 22 grams per square meter for a good result.

(If you are using Field Beans, for best results, don’t  plant legumes e.g. peas and beans in the same place afterwards so there isn’t a build up of pests and diseases which will attack your next crop).

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Hungarian Grazing Rye (Secale cereal)

Hungarian Grazing Rye is in the Gramineae family (cereal grain crops).  It can be planted between August and November and they will grow overwinter.

Hungarian Grazing Rye is happy in most soils but it doesn’t fix nitrogen like some other green manures do.  However, it is very good for improving soils, especially clay and it is great to use before a potato crop.

The Hungarian Grazing Rye needs to be sown at 16 grams per square meter for a good result.

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If you are thinking of planting a green manure at this time of year, you can plant both the above Green Manures together in alternate rows if you want to, to improve weed control.

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If you grow either of the above Green Manures, leave them to grow overwinter and cut them down three or four weeks before you want to use the ground again (or if the plant starts to flower).

After chopping the plants down, it’s easier to let the foliage wilt before you dig the plants into the soil.  Grazing rye can be hard to dig in, so you may need to ‘roughly’ dig it in first and then repeat the process again a week later.

I hope this information will help someone.

Thank you for reading my blog today.

 

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8 thoughts on “Green Manures & Can You Sow Them Now?

  1. I’ve got a bag of broadbeans that are a couple of years old, I wouldn’t want to rely on them for a crop, do you think its worth planting them as a green manure?
    Thanks Marise

    • Some broadbeans are hardier than others (aquadulce is the usual winter hardy variety), so it depends what variety they are and yes they are nitrogen fixing so they will benefit your next crop.
      One thing to mention though is broadbean seeds do last for several years, so if it was me I would use them anyway for a crop.

      • Thanks, I’ll give them a go then. Not sure which variety, they were given too me when we got the plot but I’ve got nothing to lose : )

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