Principal soil functions pertaining to agricultural land use and forestry include: (1) primary productivity, (2) water purification and regulation, (3) carbon sequestration and other aspects of climate regulation, (4) provision of a habitat for functional and intrinsic biodiversity and (5) nutrient cycling and provision. 

Scientific discipline dealing with distribution of soil types in landscapes, describing this distribution according to geographical rules.

The capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation. 

That aspect of soil quality relating to soil properties that change as a result of soil use and management or over the human time scale.

That aspect of soil quality relating to a soil

Measures that result in improved soil quality or soil health.

Cropping systems can be considered soil-improving if they result in an improved soil quality, i.e., in a durable increased ability of the soil to fulfil its functions, including food and biomass production, buffering and filtering capacity, and provision of other ecosystem services.

Soil management concerns all operations, practices, and treatments used to protect soil and enhance its performance, including regulation of soil quality. Some operations may deteriorate soil, such as the use of heavy machinery.

The total organic matter in the soil. It can be divided into three general pools: living biomass of microorganisms, fresh and partially decomposed residues (the active fraction), and the well-decomposed and highly stable organic material. Surface litter is generally not included as part of soil organic matter.

Creatures that spend all or part of their lives in the soil.