Answer:
Physical indicators are related to the arrangement of
solid particles and pores. Examples include topsoil
depth, bulk density, porosity, aggregate stability, texture,
crusting, and compaction. Physical indicators primarily
reflect limitations to root growth, seedling emergence,
infiltration, or movement of water within the soil profile.
Chemical indicators include measurements of pH,
salinity, organic matter, phosphorus concentrations,
cation-exchange capacity, nutrient cycling, and concentrations of elements that may be potential contaminants
(heavy metals, radioactive compounds, etc.) or those that
are needed for plant growth and development. The soil’s
chemical condition affects soil-plant relations, water
quality, buffering capacities, availability of nutrients and
water to plants and other organisms, mobility of contaminants, and some physical conditions, such as the
tendency for crust to form.
Biological indicators include measurements of microand macro-organisms, their activity, or byproducts.
Earthworm, nematode, or termite populations have been
suggested for use in some parts of the country. Respiration rate can be used to detect microbial activity, specifically microbial decomposition of organic matter in the
soil. Ergosterol, a fungal byproduct, has been used to
measure the activity of organisms that play an important
role in the formation and stability of soil aggregates.
Measurement of decomposition rates of plant residue in
bags or measurements of weed seed numbers, or pathogen populations can also serve as biological indicators of soil quality.
Explanation:
