Green Manures

Green Manures have a number of uses such as weed suppression on bare ground (some can even be sown under growing crops), water preservation, nitrogen fixing, improving soil health and structure, pest control, adding organic matter and attracting insects.  Most species are only used for a short period of time, but some can be left for 2 - 5 years, if you haven’t used them before we would recommend giving them a try.

Sow green manures wherever bare ground becomes available to suppress weeds.  During the main growing season Buckwheat, Crimson Clover, Fodder Radish, Mustard, Italian Ryegrass, Vittasso Mustard, Persian Clover, Phacelia, Red Clover and Vetches are the best species to sow. For over winter use, Ryecorn, Italian Ryegrass, Phacelia, Red Clover, Vetches and Alsike would be most beneficial and for inter-row sowings use White Clover, Trefoil, Perennial Ryegrass and Persian Clover.

In gardening terms a living mulch is a crop that is sown with a main crop, such as a low growing white clover sown around fruit canes or red clover sown under sweetcorn; please remember that not all green manures are appropriate to be sown with all crops as they can compete too heavily for water and nutrients and could suppress the crop you really wanted to grow! Also it is important to think about your overall crop rotation plan whilst considering which living mulch to sow.

Longer term though these living mulches should help to conserve and retain vital soil moisture. For some useful tips on saving water please click here. You can of course cut your mulch to kill it and let it lie on the top of the soil as a dead mulch whilst it decomposes and then dig it into to the soil to improve soil quality and provide a wealth of organic matter, although we do not recommend digging in until after your main crop is harvested.

Buckwheat, Fodder Radish, Italian Ryegrass, Mustard, Vittasso Mustard, Perennial Ryegrass, Phacelia and Ryecorn are great for holding nutrients in the soil.  All leguminous green manures, leave free nitrogen which has been 'fixed' from the air by bacteria living in nodules in the roots. Once ‘dug in’, the crop breaks down releasing nutrients to the following crop, reducing the need for fertilisers. Green manures that will fix nitrogen include Alsike, Crimson Clover, Fenugreek, Field Beans, Lupins, Persian Clover, Red Clover, Trefoil, Vetches and White Clover.

All green manures will improve soil and structure but Ryecorn and Vetches are particularly good overwinter and Lupins and Lucerne have the ability to penetrate deeper into the soil than other green manures, both also fix nitrogen.

Several green manures also have the beneficial side effect of being able to reduce certain soil pests such as wireworm (mustard can help with this) and nematodes for which Fodder Radish can help.  Vittasso mustard can also be used as a bio fumigant and general soil cleanser.

A number of green manures such as Phacelia, Field Beans, Clovers, Lupins and Vetches will also attract beneficial insects, this is not only a great advantage to us as gardeners but also serves to help our hard pressed invertebrates.