Background

Soil is a complex system with interrelated processes, including elements of the atmosphere, biosphere, lithosphere, and hydrosphere, which can affect soil health. Soil health, on the other hand, is a multi-dimensional concept that involves (i) soil quality to support crop production, (ii) soil fertility to enhance crop and economic productivity, and (iii) soil security to sustain its value as shared resources (Stankovics et al., 2018). However, the quantification of soil health is a complex process that depends on various physical and biogeochemical cycles and socioeconomic factors that can vary over time and space (Lehmann et al., 2020). Soil health is the continued capacity of soil to function as a vital living ecosystem capable of sustaining plants, animals, and humans. Other terms such as soil fertility, security, and quality also emphasize soil's role in society, ecosystems, and agriculture. Hence, quantifying soil health is critical for food security and sustainable agriculture, even though it is an elusive and ambiguous concept (Janzen, 2021). Granting all this, concepts like soil quality and health are necessarily tied to a specific use of the soil for which it is calculated (Baveye, 2021).

Accordingly, to define soil health, specific soil parameters concerning a specific soil ecosystem service need to be assessed (Baveye, 2021). Therefore, being able to define soil health as an overarching principle (Lehmann et al., 2020), and finding a numerical index for it, will need a lot of effort and research to answer all the questions regarding this concept (Baveye, 2021).

Defining soil health strongly depends on various indicators, parameters, aspects, and social expectations of soil (Lehmann et al., 2020). Generally, soil health is not a single phrase to be defined but may be regarded as a metaphor (Janzen 2021). Many soils’ physicochemical parameters are easily measurable, including pH, EC, bulk density, soil texture, soil moisture, organic carbon concentration, etc. The question is how many properties of soil and in which range of numbers define soil as healthy?

Many studies have shown the negative impacts of conventional farming on plant growth, environmental animal and human health, greenhouse gas mitigation, and soil health. In intensive agriculture, “essential nutrient deficiency” and “physical damage to soil structure” increase. This, therefore, changes nitrogen cycling, carbon sequestration, nutrient and water uptake by plants, pathogen control, and climate change mitigation.

On the other hand, regenerative agriculture, that is, the use of less destructive practices, helps improve the conservation of more diverse and functional microbial communities in heterogenous environments, according to research. Organic farming results in higher terrestrial microbial richness, the abundance of fungal and bacterial communities, an increase in plant growth and promoting bacteria, improves soil quality, facilitates the decomposition of soil organic materials for crop use, increases soil moisture, and many other positive impacts on soil ecosystem services.

Regenerative agriculture involves carefully controlling livestock density and how long a particular pasture or paddock is grazed at one time. It is a conservation and rehabilitation approach to food and farming systems. It focuses on topsoil regeneration, increasing biodiversity, improving the water cycle, enhancing ecosystem services, supporting biosequestration, increasing resilience to climate change, and strengthening the health and vitality of farm soil.

Conventional farming, also known as traditional farming or industrial agriculture, refers to farming systems that include synthetic chemical fertilizers, pesticides, herbicides, and other continual inputs, genetically modified organisms, concentrated animal feeding operations, heavy irrigation, intensive tillage, or concentrated monoculture production. Thus conventional agriculture is typically highly resource-demanding and energy-intensive but also highly productive.

SOM is related to nearly every soil-related ecosystem service, including water and nutrient cycling, habitat for biodiversity, and erosion control (Wall et al., 2012). Increases in SOM are likely mediated by greater aggregation, as aggregation is one of the primary mechanisms of SOM stabilization via physical protection and microbial habitat (Tisdall and Oades, 1982; Gupta and Germida, 2015).

Research Objectives

1. Evaluate how total soil organic carbon and nitrogen differ in land management practices and whether this difference is consistent in different soil layers.

2. Assess how soil properties affect the difference in soil total carbon stock and nitrogen in different layers under different management practices.

Hypotheses

The hypotheses of this research are (i) there is a negative correlation between soil organic carbon and intensive agriculture. In areas with organic-based and no-tillage farming, the total organic carbon in soil is higher. (ii) there is a direct correlation between soil physical and chemical properties and soil organic carbon. In areas with sustainable and proper physical and chemical properties, the mass of soil organic carbon is higher.