Table of Contents
Garden Soil :Nutrients Organic or Mineral!
The fertility of a soil is its ability to meet the nutritional needs of plantations. A fertile soil allows the roots to develop properly and provides plants with the water, air, and nutrients they need. A soil can be defined by its depth, the layout of its layers, its texture, its structure, its composition in organic matter and minerals.
Why fertilize a soil?
When a soil is grown, plants take their nutrients. Without input, the soil may become depleted either globally or in some elements (which is why we often avoid cultivating the same plant several times in the same place).
Several agricultural practices such as agroecology can limit or even curb this impoverishment. Transposed to the vegetable garden, this would be to cultivate only more robust and durable species in association with other plants, by bringing to the kitchen garden the remains of cooking and other organic waste, the excrement of the farm animals (chickens …) etc. As a general rule, the use of “forced” soil fertilization is more often used, if only to grow more productive varieties more quickly.
The purpose of fertilization is, therefore, to provide the necessary elements so that the soil can provide the plants with a balanced and sufficient diet. The main plant nutrients are nitrogen (N), phosphorus (P) and potassium (K). In addition, they require mineral supplements: iron, magnesium, calcium, sodium, etc.
Natural soil fertilization
The key to natural fertility is the maintenance of the hummus, that is to say, the upper layer of soil, resulting from the decomposition of organic matter. It forms with the clay a complex that retains the water and the mineral elements and redistributes them to the plants as and when they need them. A soil can also be amended, that is to say, made more or less acid, more or less light, by contributions of peat, sand, chalk. But you can never change it completely. Rhododendron vegetates and dies in calcareous soil, even if you offer it cubic meters of muck!
What are the fertilizers?
The various missing elements are brought to the soil by means of fertilizers.
There are several types of fertilizer:
– Organic fertilizers come from plant and animal waste: compost, manure, commercial fertilizers of organic origin.
– Mineral or inorganic fertilizers can be natural or produced by synthesis.
–Natural mineral fertilizers: basalt powder, lava, limestone …
Mineral or organic?
It is often used at home and in so-called “conventional” agriculture, mineral fertilizers containing one or more of the nutrients mentioned above. The main disadvantage of mineral fertilizers is that they are easily assimilated by plants … and therefore also easily reached by the rains. This is particularly the case of nitrates.
In case of bad application, it contributes to water pollution, nitrates being very soluble. In excess, nitrates participate in the eutrophication of streams that is manifested by the proliferation of algae. These, by consuming the oxygen of the medium, cause its asphyxiation and sometimes its death (eutrophication). In the aquifers, the massive presence of nitrates compromises the use of groundwater as a source of drinking water. The abuse of chemical fertilizers can also lead to a gradual disappearance of humus.
In our body, they can turn into toxic and carcinogenic nitrites. This is not the only drawback of these fertilizers: some chemical fertilizers like superphosphates, for example, contain heavy metals (cadmium, mercury, lead, zinc …). The risk of these metals passing through plants and contaminating food chains is not negligible; it is even important in the case of cadmium.
It will, therefore, be advantageous to use organic fertilizers, plant (nettle purines, compost …) or animal (blood, bone, horn, manure …). In the case of organic fertilizers, the elements are not directly free and assimilated but “locked up”. It is the action of soil bacteria that allows the progressive release of the elements so that they are assimilated by plants. The effect is slower but longer. This also limits leaching problems.
The best fertilizer (Nutrients): The Compost
The best organic fertilizer is compost. He brings in the same time of humus and nutrients. However, adding another organic fertilizer can be helpful. A green manure can be a good complement to the vegetable garden (for example, mixing the foliage of the beans with the ground, cabbage…). The choice of other fertilizers depends on the nutritional needs plants and soil characteristics. These last can be determined by a soil analysis. Mineral powders enrich the soil with trace elements (specific to each powder) and increase retention water and nutrients through the soil.
Clay powders are, like bentonite or montmorillonite, rich in clay minerals and are mostly used for sandy soils. The clay powders swell strongly with water and improve the soil‘s ability to fix nutrients. Limestone is used to correct soil acidity. It stimulates biological activity, it improves the granular structure and makes nutrients more assimilable. Exaggerated additions limestone can decrease humus formation ability. The peat maintains a favorable humidity but it makes the acidic soil. It comes from wetland areas threatened with destruction: do not use it in our garden.
Bark humus comes from the composting of added bark nitrogen. It is rich in organic matter and replaces advantageously peat when its pH is around 6.
Mulch is composed of organic matter roughly chopped (lawn mowing, straws, dried leaves, seeds, bark …) but it is poor in nutrients. He can be used to cover the ground and protect it from the cold in winter and drying out in summer.