Our 100% natural garden fertilisers

What does fertiliser actually mean?

Fertile soil rests on a fine balance between physical criteria related to depth or structure, but also on the presence of nutrients and water, and an active pedofauna (bacteria, fungi, earthworms, insects…)

Thus, fertilising your soil amounts to supplying it with essential nutrients (nitrogen, phosphorus, potassium…) to nourish it and thereby stimulate plant growth.

However, a soil amendment can also influence soil structure to improve water retention and air movement, thereby facilitating the rooting of plants.

Fertilise soil by nourishing it with amendments to promote plant growth. By contrast, applying fertilisers nourishes the plants.

Compost, to improve soil fertility and feed young plants

Composting is giving back to nature what belongs to it; it is reproducing, at the scale of your garden, the cycle of that same nature, and it nourishes your soil in a completely natural way.

Composting, an ecological gesture

Indeed, bringing compost to your garden mirrors what naturally happens in nature, for example in a woodland floor: plant debris such as dead leaves, broken twigs… and animal debris (excrement, moults, hairs and feathers…) settle on the soil as the seasons pass. Then come the microorganisms that make up the soil fauna. These insects, these microbes, these bacteria, these fungi feed on these organic debris and ensure their decomposition. All this waste forms humus, rich in minerals (nitrogen, phosphorus, potassium, calcium…) and in carbon, which nourishes the plants and promotes soil life. The cycle is closed and unchanging from year to year.

Compost is an excellent fertiliser for the soil

In the garden or the allotment, it is impossible to reproduce this natural cycle. Simply because any gardener worth their salt tends to remove weeds and organic waste. Likewise, given the number of cultivated plants, the soil wears out more quickly than in the woodland floor. And it does not have the capacity to replenish its resources. Hence the addition of compost, derived from the decomposition of organic waste, from the kitchen or the garden.

What makes good compost?

As in nature, a good compost must consist of a wide diversity of organic debris, both moist and green (grass clippings, fruit and vegetable peelings, adventives…), rich in nitrogen, and dry or brown (crushed dry twigs, wood chips, straw, dead leaves…), interesting for their carbon content. These wastes decompose at varying rates (roughly 6 months to a year) thanks to the work of microorganisms. But for the decomposition process to function properly, oxygen and moisture are also necessary. Hence the need to turn and water the compost to aerate and moisten it.

Once mature and well decomposed, the compost is spread over the soil. All that is required is to rake the surface to incorporate it superficially. And this can be done at any time of year, whether to enrich the soil of the vegetable plot or of beds, hedges and borders. The compost also blends with the planting soil for perennials, bushes and trees.

Whether you compost in a heap, in a silo, in a compost bin, or indeed in surface composting on the surface or underground, in a trench, or even via a vermicomposter or the Bokashi method, it doesn’t matter—the essential thing is to compost. For gardeners who don’t know how to compost (or don’t want to), they can find ready-to-use compost sacks. Or they can turn to community composting platforms that are developing in local authority areas.

Composting is worth it because:

• Compost improves soil fertility
• It regenerates tired and poor soils
• It brings life back and attracts microorganisms
• It lightens and improves the structure of the heaviest soils
• It aids water retention and reduces watering frequency
• It promotes plant growth and protects them from diseases
• It limits temperature fluctuations…

As a reminder, composting of household organic waste has been mandatory since 1 January 2024.

To learn more about composting:

• Succeed with composting in 5 steps
• Compost: where and how best to use it in the garden?
• Organic waste: what can be composted?
• What waste should not go into the compost?
• How can I speed up the decomposition of compost?

Manure, an interesting addition to compost

If there is one organic amendment used since ancient times, it’s manure. Composed of excrement and urine of domestic animals mixed with their litter (most often straw), manure is very rich in mineral elements, at around 28 to 30%. Sometimes more than compost depending on the type of manure which may come from cattle (cows), equines (horses and donkeys), small ruminants (sheep and goats), pigs, poultry (hen droppings) or rabbits. Sheep manure is very rich, followed by horse manure. As for hen droppings, they must be used with caution, as they are very high in nitrogen. In short, each manure has different characteristics, more suited to such and such soil.

Manure comes in different forms. It can be collected raw and fresh directly from a farmer, an equestrian centre or a breeder. It can be obtained in a ready-to-use, pre-decomposed bag. And, in recent years, there is also pelleted manure, very practical to use and to spread. Naturally, depending on the type and form of manure, applications are made at different times. Thus, raw manure is used only in autumn, spread on the soil. But the ideal is to compost your manure for a few months to eliminate any traces of adventive weeds, pathogenous genes or medicines administered to the animals. Manure is also perfect for making hot beds.

Composted for at least 6 months, manure is a very good soil amendment

Manure should therefore be used in addition to compost to improve the soil by adding humus, to increase the soil’s permeability, to aerate it, to lighten it, or, conversely, to give it body, and finally to enrich it with microorganisms.

Further reading:

• When and how to use manure in the vegetable garden?
• Manure: 10 mistakes to avoid
• Manure in 10 questions and answers
• Pelleted manure: how to use it well in the garden?

Green manures, fast-growing plants to be dug into the soil

Like compost and manure, the green manures enrich the soil, notably in nitrogen and humus, but also help to raise mineral elements drawn from depth, while improving its structure through their root systems. Indeed, fertilising the soil with green manures involves cultivating specific plants, then burying them or letting them decompose. Beyond their fertilising quality, green manures prevent the proliferation of weeds by occupying space, limit soil erosion, especially in winter, stimulate soil biological activity and even attract and feed pollinating insects through their melliferous and nectariferous flowering.

There are three types of green manures with different properties. Depending on the soil’s deficiencies, one can sow Fabaceae (formerly Leguminosae) such as vetch, the clover, the sainfoin, the fava bean, or peas, all of which have the ability to capture atmospheric nitrogen and return it to the soil. Among green manures, there are also Brassicaceae such as mustard or rapeseed, ideal for sandy and poor soils. Or grasses such as the rye, the buckwheat, oats… to be grown in association with Fabaceae. Phacelia is also regarded as an excellent green manure.

Clover, sainfoin, vetch, mustard and phacelia are green manures to sow and bury in the soil

There are two sowing periods for green manures: spring (just before summer vegetables are planted) and autumn. Certainly, they occupy the ground for 2 to 3 months, but the benefit is not negligible!

For further reading: Green manures: Why? How?

Plant manures and plant decoctions, with phyto-stimulant and fertilising effects

When we talk about plant manures and decoctions, we mainly think of their benefits in combating diseases and repelling pests. In short, these plant-based preparations are often equated with insecticides or fungicides, reputed for their curative as well as preventive action. They are also excellent fertilisers for plants and good soil fertilisers.

Beyond its insecticidal and fungicidal properties, nettle manure fertilises the soil

Thus, some plant-based manures or decoctions, fermentation-based preparations that are very easy to make, are packed with essential nutrients to promote plant growth. They are usually diluted in irrigation water and applied to the soil. Each manure has different uses and properties:

• nettle manure mainly provides nitrogen to the soil
• comfrey manure is richer in potash and trace elements
• cabbage manure contains a good level of nitrogen and trace elements
• tomato manure is an effective fertiliser for fruits and vegetables (tomatoes, cabbages and squashes).

Note that nettle manure is usually applied in spring. Afterwards, comfrey manure can take over.

Leaf mould, very rich in organic matter

Leaf mould is simply the result of the decomposition of dead leaves, added to several layers of lawn clippings, manure, compost and nettle leaves… This decomposition takes place in a silo for several months to two years. This yields humus that is fairly acidic, rich in nitrogen, phosphorus and potash.

I invite you to read Virginie D.’s article: How to make good leaf mould?