Mulching is defined as the action of covering the soil with various materials. This practice is intended to protect crops from bad weather and prevent the development of unwanted weeds. Organic materials, as they decompose, will also enrich the soil. However, in the natural vegetable garden, mulching has some disadvantages: put in place too early in the season, this soil cover will prevent the latter from warming up properly. And rodents, but also slugs, like to take refuge there... Let's distinguish mulching from mulch (paillis in French). A mulch is brought in once to cover the soil for a crop; while the mulch has a more permanent and nourishing objective for the soil (we will continue to bring materials regularly on top), thus never allowing the soil to remain bare... But that's more of a rhetorical question than anything else... In practice, our objective will be, whatever the term used, to protect the soil, while nourishing it... thus giving it, over the course of the inputs and the seasons, a certain fertility.
Why mulch?
Protect cultivated plants from bad weather
Covering the soil limits the effects of climate on it and on the various life forms that thrive there. But let's see more precisely how mulching protects against bad weather:
It attenuates the consequences of a heat wave, namely excessive heating and drying of the soil (with the earth hardening until the appearance of cracks);
It helps retain rainwater and prevents gullying in the event of heavy rain;
It limits evaporation;
It attenuates the effect of sudden temperature variations and thus protects the inhabitants of the soil.
feed the soil
The “green” organic materials, easily decomposing, will be absorbed, digested and finally transformed, by the living beings of the soil, into nutrients quickly and directly available for the cultivated plants.
Thus, grass, manure (little straw) as well as all kinds of organic matter rich in nitrogen, while decomposing, provide abundant food, quickly available and particularly appreciated by gourmet vegetables.
Straw, dead leaves, strawy manure, more woody (carbonaceous) materials, by promoting the development of stable humus, will have a lasting beneficial effect on the structure and life of the soil.
Hay or RCW, for example, are rather balanced materials (between nitrogen and carbon).
And it is this search for balance that must dictate the approach to be followed in terms of mulching.
To evolve well, brown materials need the presence of green materials (the nitrogen contained in the latter favoring the decomposition of the former).
Green materials feed the plants… but not the soil.
These types of materials are therefore simply complementary.
Concretely, alternate at best, over the seasons (and therefore the materials available in a given season), the contributions of brown materials (ligneous) and green materials (nitrogenous).
And that's good...
The materials naturally available in the spring tend to be green materials (clippings, prunings, various plant residues), which will decompose in a few weeks, and thus release nitrogen and other mineral elements.
And it is these elements that will directly nourish the plants that you will grow throughout the season.
In autumn we find brown materials more easily (dead leaves, branches, straw…)…
Thanks to the addition of these ligneous materials, your soil will gradually transform into stable humus.
It will become a little more fertile each year.
Limit the development of weeds (“weeds”)
A thick soil cover will smother the weeds and thus prevent their proliferation within the crops.
Despite everything, some particularly virulent weeds (quackgrass, bindweed, rumex, etc.) will manage to cross the mulch.
But they can then be uprooted much more easily (at least after rain) than on bare ground.
Well... if you let the bindweed colonize a mulch, it could become complicated... so act quickly and regularly.