The usefulness of mulching your vegetable garden is well established, but what is the best in terms of contribution to the soil? There are a multitude of possible mulches, but none is truly perfect, in the sense that it does not entirely compensate for the needs of the plants in your vegetable garden. Thus each mulch has its own nutritional values, and brings more or less interesting elements for the soil and the crops in place.

Like human food, the food of the soil to be good and balanced must be diversified!

Mulching with straw from one year to the next will be deficient, just like soil mulched from year to year with RCW, which will tend to acidify gradually. For a few years now, I have been trying to diversify the soil supply in my vegetable garden by carrying out a kind of “mulching rotation”, alternating and accumulating different types of cover each season. This rotation helps to balance the supply of nutrients and nutrients, and helps to increase soil fertility and the general productivity of the vegetable garden.

What does this rotation actually consist of? For example, in the fall you can take advantage of the fall of dead leaves from the garden to spread them out in the vegetable garden, just like the pruning waste that you will eventually carry out during the fall. The following spring, I gradually bring in the previously dried mowing waste and finally during the summer I add another layer of hay or straw from organic farming to increase the thickness of the cover in anticipation. high summer temperatures so that the soil stays cool and retains its moisture optimally.

The main organic mulches, their advantages and their drawbacks:

– Straw : This is probably the most commonly used ground cover material. If the straw provides very good protection of soil against erosion, maintains humidity and prevents weeds. However, straw is not a very rich mulch, and brings only relatively few elements to the soil during its degradation. Its potassium content is significant, but the straw is particularly low in nitrogen and phosphorus.

Mulching of tomato plants with straw – Photograph: Lucas HEITZ /

-Hay : Like straw, hay has the advantage of being very economical. This technique of mulching with hay, sometimes called “phenoculture”, also has the enormous advantage of being free of phytosanitary treatment, unlike straw that is often treated. Although gardeners are often reluctant to hay, because of the seeds it contains, it is not yours, providing a fairly thick layer (10-15 cm), seeds devoid of light will not grow.

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-The BRF : From its real name “fragmented ramial wood”, it is a mulch made up of small discs with a diameter of less than 5 cm obtained by chopping branches generally of deciduous trees, resulting from the size. It is an ideal mulch for forest plants, such as blueberries, strawberries, raspberries or even hazelnuts. However, on vegetable growing beds, this can lead to a harmful acidification of the pH in the long term.

– Lawn mowing : Before spreading the lawn mowing as mulch, care must be taken to dry it beforehand, because disposing of it directly causes fermentation and a fairly significant heat production which can be dangerous for plants. , especially the most sensitive ones. Once in place, the dried clippings are very quickly degraded in the soil (in a few weeks), it is therefore advisable to bring another mulch in addition.

-Dead leaves: They constitute a mulch of choice in autumn and winter, however their relatively short duration of view does not allow coverage all year round. At the beginning of spring, it will therefore be necessary to compensate with another mulch. Dead leaves, however, provide significant amounts of humic substances which benefit soil organisms and improve the soil of the vegetable garden.

– Linen flakes : Resulting from the processing of flax fiber, this product comes in the form of small flakes, it is fluid, easy to handle and does not fly away. Its beige-white color reflects solar radiation and aesthetically forms a very nice contrast with the foliage of the plants. Its pH is neutral and this mulch is quite rich in organic matter. The flax will improve the physical structure of the soil. The downside is that flax doesn’t add many nutrients to the soil.

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– Hemp flakes: This is an interesting product because the cultivation of hemp requires almost no phytosanitary products or fertilizers. Its hydrogen potential (pH) is neutral. It also has a strong capacity to absorb rainwater, which can be an advantage as well as a disadvantage. It can lead to the rotting of plant roots if the rains are numerous and frequent, it is better to use hemp mulch at the foot of plantations which are particularly fond of wet soils. It is less easy to find than other mulches and its purchase price is relatively high.

– Cocoa pods: They have quite interesting agronomic characteristics with a pH around 5.7. They can therefore be used on any type of bed, border, or in the vegetable garden. In addition, their chocolate color particularly highlights the plants. Their only drawback is a slightly too high cost due to the obligation to import it, which in the end is not very ecological either!

-Pine bark: Widely used in beds, they tend to be neglected because they acidify the soil. However, large calibers, they decay slowly and can last up to 10 years. Also this type of mulching, very decorative, may be recommended for acidophilic plants, but not between your vegetable plants. You can also put it at the foot of your small fruit trees, such as raspberries, blueberries or even at the foot of shrubs such as serviceberry for example.

-Wood chips: Derived from recycled wood, it is more of a “decorative mulch” than a real nourishing mulch. We find them in all colors to the most kitsch, from raw wood color, to blue or red, passing through green or yellow. Beyond decorating, covering the soil, and protecting it from soil erosion, woodchips add little or no nutrients to the soil.

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– Shredded miscanthus : This is a grass grown mainly for its biomass for heating. Unlike other mulches, it has a perfectly neutral pH. In addition, this mulch is stable against the wind and water runoff, thus fighting against erosion. It has a high water retention capacity thanks to its composition (hollow and spongy stem). From an ecological point of view, miscanthus is grown without water (or very little), without fertilizer and without pesticides (because it has no pests). This quality mulching is unfortunately still rare and expensive, the agricultural sector being only in its infancy in France.

There are also mineral mulches (slate, pebbles, gravel, sand, etc.) or even artificial materials (tarpaulin, black horticultural plastic, felts, etc.). However, I voluntarily ignore them, since being inert these materials have the common point of bringing nothing to the soil, they are therefore of no interest in the context of a vegetable garden in which we wish to sustainably regenerate the fertility of the soil and promote its biological activity.

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