Physical properties

Chemical properties

Biological properties

Organic matter includes any plant or animal material that returns to the soil and goes through the decomposition process. In addition to providing nutrients and habitat to organisms living in the soil, organic matter also binds soil particles into aggregates and improves the water holding capacity of soil.

Heavy metals kill microbes by binding to proteins, thus inhibiting enzymatic activity. ... Ions of heavy metals bind to sulfur-containing amino acids strongly and bioaccumulate within cells, allowing these metals to reach high localized concentrations. This causes proteins to denature.

A high moisture content decreases rates of organic matter decomposition, due to low oxygen supply, while low soil moisture decreases microbial activity by reducing diffusion of soluble substrates, microbial mobility and intracellular water potential

Soil enzymes affect microbial functions and nutrient cycling, are important indicators of organic matter decomposition, and provide required microbial nutrients.

Microbial numbers were negatively and linearly related to soil bulk density. With increases in soil bulk density from 1.00 to 1.60 Mg m–3, total numbers of bacteria, fungi and actinomycetes declined by 26–39%.

Earthworms ingest plant growth-promoting rhizospheric bacteria such as Pseudomonas, Rhizobium, Bacillus, Azosprillium, Azotobacter, etc. along with rhizospheric soil, and they might get activated or increased due to the ideal micro-environment of the gut.

Soil respiration reflects the capacity of soil to sustain plant growth, soil fauna, and microorganisms. It indicates the level of microbial activity and SOM content and its decomposition. Soil respiration can be used to estimate nutrient cycling in the soil and the soil's ability to sustain plant growth.

Salinity results in poor plant growth and low soil microbial activity due to osmotic stress and toxic ions. Soil microorganisms play a pivotal role in soils through mineralization of organic matter into plant available nutrients. Therefore it is important to maintain high microbial activity in soils.

Acidic soils limit both root growth and rhizobia survival, reducing the chances of roots contacting enough bacteria to form a nodule and inhibiting the performance of nodules that do form.Under more appropriate pH levels, the activity of detrimental soil microbes can also be increased and may need to be managed.

Soil texture plays an important role in determination of bulk density of soil and in improving the soil quality as it provides isolated microhabitats for microorganisms which cause an increase in the microorganisms' diversity and abundance.Increased spatial isolation in soil systems has the potential to increase bacterial diversity. For two soils at the same water content and same porosity, a finer-textured soil would have more water-filled pores, whereas a coarser soil would have more isolated water films.

A stable soil structure is central to soil functions, including storage and transport of water and gases and turnover of organic matter, and essential for habitation of soil organisms.