Healthy soil
The preservation of soil fertility and the maintenance of “healthy soils” are fundamental components of sustainable soil resource management and sustainable agricultural development.
Under changing climatic conditions, ensuring good water quality is of critical importance. In accordance with European legislation (Directive 2000/60/EC – establishing a framework for Community action in the field of water policy), the protection and sustainable management of all water resources, including surface and groundwater, is a key requirement.
Research on agricultural sustainability requires an interdisciplinary approach, integrating knowledge from agriculture, agrochemistry, biology, economics, engineering sciences, chemistry, sociology, and other related fields. Sustainable agriculture, however, represents more than a combination of individual practices; soil constitutes one of its fundamental components and determines the capacity of agroecosystems to provide essential functions and services.
The contemporary management of the planet’s limited soil resources requires the preservation and restoration of healthy and productive soils to ensure global food security and maintain vital ecosystem services.
The definition of a “healthy soil” (FAO) depends on the intended use of the soil; however, it commonly incorporates several key soil functions, including:
Achieving the objectives of sustainable agriculture requires the implementation of appropriate land-use policies, reflected in the development and application of eco-schemes and environmentally sustainable agricultural practices. The evaluation of land-use systems, including organic, conventional, and conservation agriculture under irrigated conditions, will enable a comparative assessment of agrochemical and biological changes occurring in soils. Indicative studies have demonstrated various approaches for evaluating soil ecological status. For example, bacterial activity and physiological diversity of soil microbial communities have been successfully characterized using Biolog EcoPlate™ assays. These assays provide a sensitive and reliable indicator of environmental changes by assessing the functional diversity and metabolic potential of microbial communities. The quantitative and qualitative profiles obtained through such analyses represent the metabolic fingerprint of microbial communities and are directly linked to alterations in soil processes and ecosystem functioning.
Maintaining soil fertility and managing the carbon balance are essential components of sustainable soil management. Soil organic carbon (SOC) represents the main fraction of soil organic matter and plays a fundamental role in regulating key soil processes. SOC levels may vary considerably depending on natural factors, including climate, land cover, and soil parent material, as well as anthropogenic factors related to land use and management practices. Compared with European agricultural soils, Bulgaria is among the countries characterized by a negative to neutral SOC balance. This indicates that carbon losses may exceed carbon inputs and sequestration, potentially leading to soil degradation, depletion of soil organic matter, and reduced biological activity of soil organisms. Maintaining soil structure, quality, and ecosystem functions, while increasing SOC stocks, requires the implementation of appropriate sustainable land management practices. Agricultural carbon sequestration can be enhanced through improved soil management strategies, which directly influence soil organic carbon storage and long-term soil resilience.
Maintaining a balanced soil organic matter status and preserving or increasing nutrient stocks through modern agricultural practices requires an integrated set of management measures, including appropriate soil tillage practices, hydromelioration activities, balanced mineral and organic fertilization, reduced pesticide inputs, and the incorporation of processed or composted organic wastes into the soil. The depletion of nutrients in agricultural soils is associated with the loss of topsoil due to erosion processes, accelerated oxidation of soil organic carbon under intensive cultivation systems, inappropriate agricultural management, degradation of soil structure, soil compaction, and other degradation processes. The nutrient status of soils is commonly assessed through the determination of total nitrogen, soil organic carbon, and total phosphorus contents, as well as the soil organic carbon-to-total nitrogen (C) ratio. The concentration and balance of these biogenic elements are directly linked to soil fertility, nutrient cycling, and plant nutrition.