Environmental pressure and rising fertiliser prices are now driving a new approach to soil functioning. The article “A cost-effective living soil approach” explains how soil flora helps maintain the stock of nutrients available to plants.
Stimulating soil flora should lead to the stimulation of all the microorganisms it contains, while maintaining two key balances:
- the balance of organic matter
- the balance of microbial populations.
Step 1: balance of organic matter
From straw to humus, organic matter is constantly evolving under the action of various microorganisms, much like a food chain in which “one organism’s leftovers become another’s meal”.
Each type of organic matter has a primary role and a secondary role. Fresh organic matter forms a reserve of nutrients in organic form, while stabilised organic matter helps fix nutrients in mineral form by protecting them from leaching. An imbalance in soil organic matter therefore leads to a loss of fertility: either through a reduction in organic reserves or through increased leaching.
Two approaches are currently available to stimulate soil flora:
The use of commercial solutions based on bacteria promotes a single step in the degradation chain, thereby increasing imbalance.
By strongly breaking down one fraction, this approach delivers an immediate fertilising effect but degrades soil fertility and structure in the long term by accumulating the next form of organic matter in the chain.
Stimulating the entire soil flora helps accelerate the whole chain. Although this approach is slower than the first, as it takes around three years to restore a good balance, it sustainably improves chemical fertility (increased mineralisation and CEC) and soil structure (greater humus content).
Step 2: balance of microbial populations
The balance of microorganisms in soil depends on two factors: the balance of organic matter, which provides their food source, and the balance between prey and predators.
A diverse crop rotation, through the succession of different crops, makes it possible to successively stimulate different microbial populations at varying levels of intensity.
Conversely, monocropping promotes the emergence of pathogens, as it provides them with a constant food source.
Prey–predator interactions among soil microorganisms
Efficient degradation of organic matter, from fresh material to humus, helps reduce the amount of food available at each stage for soil flora.
For example, cereal straw (wheat, maize) acts as a soil reservoir for Fusarium diseases. If these residues disappear quickly after harvest, disease pressure on the following crop will be reduced.
As in any ecosystem, microorganisms interact with one another within the soil. The prey–predator balance determines the evolution of soil microbial balance.
The example of pseudomonads and their predators perfectly illustrates these interactions.
In their 1984 study “Invertebrate–microbial interactions”, published by Cambridge University Press, Anderson and colleagues showed that under the effect of nematodes, populations of Pseudomonas putida decrease due to predation.
In response, the bacteria become more active (increased nitrate production), thereby altering the balance of organic matter.
Prey–predator interactions among macro-organisms
The main risk arises once predator populations have significantly reduced prey populations. When predator numbers become too high relative to available prey, predators may turn to secondary prey, which can include cultivated plants. This phenomenon is particularly observed with nematodes.
Final thoughts
Stimulating soil flora is a solution to increase farm autonomy with regard to fertilisers.
The return on investment of such an approach can make it possible to achieve full autonomy in phosphorus (P) and potassium (K) and to double the soil’s potential nitrogen supply to crops.
However, this practice must be carefully managed, both in terms of organic matter inputs to the soil (crop rotation, spreading, cover crops, etc.) and in terms of soil flora balance (regular stimulation of the entire soil flora and maintenance of existing populations).
Environmental pressure and rising fertiliser prices are now driving a new approach to soil functioning. The article “A cost-effective living soil approach” explains how soil flora helps maintain the stock of nutrients available to plants. Stimulating soil flora should lead to the stimulation of all the microorganisms it contains, while maintaining two key balances: the […]
...Environmental pressure and rising fertiliser prices are now driving a new approach to soil functioning. The article “A cost-effective living soil approach” explains how soil flora helps maintain the stock of nutrients available to plants. Stimulating soil flora should lead to the stimulation of all the microorganisms it contains, while maintaining two key balances: the […]
...Environmental pressure and rising fertiliser prices are now driving a new approach to soil functioning. The article “A cost-effective living soil approach” explains how soil flora helps maintain the stock of nutrients available to plants. Stimulating soil flora should lead to the stimulation of all the microorganisms it contains, while maintaining two key balances: the […]
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