Green manures are great at suppressing weeds and increasing the fertility of your soil. As well as many other benefits they are a great organic alternative to artificial fertilizers.
They can be sown at most times of the year but are particularly useful over winter, before Spring. Growing a green manure over winter when plots are empty will stop nutrients and soil being washed away, they can add structure to the soil and when dug in add valued nutrients. They are valuable as part of a crop rotation cycle, particularly before nutrient hungry crops.
How to grow a green manure
- Remove any weeds from the plot and dig over if required
- Spread the seeds evenly according to the instructions from the seed supplier. (e.g grazing rye, 250g covers 15 square metres)
- Rake over or firm down the seeds and water in
- Most green manures will cover the ground within 2 to three weeks. Leave in for at least eight weeks or before flowering. Younger plants are easier to dig in.
- When ready dig the whole plant into the soil and leave for around two weeks to a month to decompose in the soil.
- If you leave the green manure a bit to long and find it difficult to dig in it will make excellent nutrient rich compost.
Green manures can also be grown over a longer period (several seasons). This is useful if you have extremely poor soil or are having trouble controlling perennial weeds in your plot. They can also be cut for digging in and adding nutrients to other areas, as a mulch which will release nutrient slower or for composting and some are also very attractive to wildlife when they flower.
Which green manure to choose? Basically you can choose between legumes and non-legumes. Legumes (eg Field beans) can fix nitrogen in the soil which is released when dug in, Non-legumes produce more organic matter and tend survive more extreme weather.