14 August 2015
I have recently been reading about the benefits of green manures so have decided to try one in my raised vegetable beds, sowing the seeds after harvesting my broad beans and onions. Below are listed some of the benefits of green manures:-
As they grow they form a green carpet that suppresses weeds.
Some can absorb nitrogen from the air, which is transferred to the roots and released when dug into the soil, which is good for the vegetables that follow.
Growing a green manure in winter prevents nutrients being washed away from the soil by rain or snow.
Some varieties have a fibrous root system that helps to give the soil structure.
Clover is a green manure that can be left to grow for a year, and its flowers attracts bees and other pollinating insects.
Green manures are particularly useful to vegetable gardeners and are ideal whenever a patch of land is going to be free of crops for six weeks or more. Although many green manures can be sown all year round, they are ideal when sown in the autumn to overwinter, when vegetable plots are generally empty.
Before planting your green manure, prepare the soil by removing weeds and then digging it over and raking it level.
Scatter seeds over the surface of the soil using the amount per square metre recommended by the seed supplier. This varies according to the variety you have chosen.
Ensure that the seed is in firm contact with the soil by gently tapping over the surface with the back of a spade, then water it in well.
Bare patches should be covered within two to three weeks.The most benefit will be gained if plants are left for around eight weeks before digging in. If plants start to flower before this, cut off the tops and dig in. After digging in the manure, leave it to decompose in the soil for up to four weeks before growing vegetables.
Some popular plants to try are:-
Crimson clover (Trifolium incarnatum): A perennial legume, good for light soils; sow from March to August and leave in for two or three months up to flowering.
Mustard (Sinapis alba): Sow this annual crop between March and September and leave for two or three months before digging in. As it is a member of the brassica family, it shouldn't be followed by other brassicas, as it could encourage build up of the disease clubroot.
Grazing rye (Secale cereale): An annual crop which is good for soil structure and overwinters well; sow in August to November and dig in the following spring.
Winter tares (Vicia sativa): This annual legume overwinters well, and is useful for heavy soils; sow either in March to August and leave for two or three months before digging in, or sow in July to September for overwintering.
Winter field bean (Vicia faba): Another annual legume which is good for heavy soils. After sowing, between September and November, it can be left for two or three months (up to flowering).
Most vegetable gardens will have some bare areas after harvesting, so why not try a green manure. I planted mustard seeds in July in two small areas of my raised beds as a trial, and they have germinated successfully, so I intend to plant up some more areas as they become available.