Soil is a complex living network composed of bacteria, fungi, protozoa, nematodes, and many other organisms. These organisms regulate critical processes, from the decomposition of organic matter and nutrient cycling to forming symbiotic relationships with plant roots and indirectly supporting water retention capacity. As emphasized by FAO and various soil science studies, a handful of healthy soil contains billions of microorganisms, and the diversity and activity of these organisms directly determine soil functionality. When this structure weakens, the soil may still exist physically, but begins to decline functionally.

One of the main causes of yield loss is the disruption of this biological balance. Intensive use of chemical inputs in modern agriculture may meet the plant’s immediate nutrient needs in the short term, but in the long run, it can suppress microbial diversity and activity in the soil. Monoculture systems allow certain microorganisms to dominate continuously, narrowing the ecological balance. Continuous soil tillage physically disrupts soil structure and damages microbial habitats. A lack of organic matter removes the primary energy source of this system. Together, these factors gradually reduce the biological capacity of the soil.

A critical aspect of this process is that yield loss is usually recognized not through its causes, but through its consequences. Plants begin to have difficulty accessing nutrients, water use becomes inefficient, root development is restricted, and plants become more vulnerable to stress conditions. However, by the time these symptoms become visible, the biological structure of the soil has often already been significantly weakened. Conventional soil analyses mainly focus on chemical parameters such as pH and macro- and micronutrient levels, and therefore fail to adequately reflect these biological changes. As a result, the root cause of the problem remains unseen.

When productivity declines, the most common response is to increase inputs. Higher fertilizer use or more intensive interventions may provide short-term results. However, this approach often deepens the problem rather than resolving the underlying dysfunction. This is because the issue is not how much nutrient the soil contains, but how effectively those nutrients are cycled and made available to plants. When biological processes in the soil are weakened, even existing nutrients cannot be efficiently utilized.

Plant productivity depends on the interaction of physical, chemical, and biological components. When one of these components weakens, the entire system is affected. However, the biological component acts as the central mechanism influencing the other two. Microorganisms break down organic matter, making nutrients available to plants, contribute to soil aggregation and improve physical structure, and enhance plant resilience to stress through interactions in the root zone. Therefore, the biological structure is not just one component, but the core system regulating overall soil function.

Research shows that soils with high microbial diversity provide more stable yields, improve water and nutrient use efficiency, and increase plant resistance to abiotic stress. In contrast, biologically degraded soils become increasingly dependent on external inputs, and sustainability declines. This leads to higher economic and ecological costs in the long term.