How application of chemicals, including fertilisers, affect the soil microbiome and plant health?

Yes, the application of chemicals, even fertilizers, can have a significant impact on the beneficial microbial population. Let's explore how.

The soil microbiome, a community of diverse microorganisms, is influenced by various factors, including moisture, organic matter content, oxygen levels, pH, plant exudates, and microclimate. When fertilizers are applied, the soil's nutrient status changes, leading to corresponding shifts in the microbial population. Initially, as nutrients become available, plants may reduce the secretion of exudates that specifically induce certain microbial populations to function. However, excessive nutrient levels can alter the soil's pH and redox conditions through geochemical and biochemical processes. Ultimately, the need for specific microbial populations, such as nitrogen-fixing or phosphorus- and potassium-mobilizing bacteria, may diminish. Without plant support through exudates, these microorganisms may struggle to survive and fulfill their ecological roles within the microbiome.

In essence, a naturally undisturbed soil maintains a delicate ecological balance with all its interdependent species. The system is optimized for efficient functioning with minimal energy input. Any external intervention, such as the addition of fertilizers, can disrupt this equilibrium, leading to inefficiency in overall biogeochemical processes. Therefore, preserving this delicate balance is crucial, especially in natural farming systems.

Please note that different fertilizers can have varying impacts on the soil microbiome, and their application rates can also influence soil characteristics.

Organic fertilizers, which release nutrients more gradually, can support the existing microbial population. Inorganic fertilizers, on the other hand, dissolve quickly and can potentially create conditions that favor the growth of various microbial populations, including some that may be pathogenic.

Additionally, soil type plays a role in how microbial populations are affected by fertilizer application. In clayey soils, some nutrients may be adsorbed, while certain bacteria may find refuge within the fine clay particles, providing protection from harmful conditions. Sandy soils may have different characteristics, such as lower nutrient retention and less protective properties for microorganisms. Moreover, the varying availability of micronutrients in different soil types can impact the growth and activity of various microbial groups.

How can we maintain good soil health without harming the soil microbiome and its ecological balance?

By cultivating specific cover crops, intercropping, and companion plants alongside agricultural crops, we can sustainably nurture the beneficial microbiome in the soil. This not only prevents the onset and spread of plant diseases but also maintains adequate levels of soil nutrients through plant-microbial interactions that mobilize essential nutrients from the soil via natural mineral dissolution. This is the direction agriculture should take to achieve sustainability.

Lastly, it's advisable to grow plants that are naturally suited to your soil. Avoid hybrid varieties that may place excessive demands on soil nutrients. Excessive irrigation, similar to overeating, can negatively impact oxygen diffusion into the soil.

As much as possible, we should avoid tillage, practice multicropping, utilize grass cycling, and integrate livestock into our farming system. Cattle dung is a valuable source of beneficial organisms that we can harness without the need for costly market purchases.

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