Physical Properties of Soil.

Abstract

Physical properties of soil include color, texture, structure, porosity, density, consistence, temperature, and air. Colors of soils vary widely and indicate such important properties as organic matter, water, and redox conditions. Soil texture, structure, porosity, density, and consistence are related with types of soil particles and their arrangement. There are two types of soil particles---primary and secondary. Primary particles include sand, silt, and clay, categorized on the basis of their effective diameter. There are important differences in physical, chemical, and mineralogical properties of these fractions. Their relative proportion in a soil is called soil texture. It is a fundamental property of soil. It is not easily altered. There are 12 textural classes ranging from sand to clay. Soil structure is the arrangement of soil particles into different geometric patterns. It is classified into different types on shape, classes on size, and grades on stability. Soil structure is amenable. Soil texture and structure together regulate porosity, density, compactness, retention, and movement of water and air in soil. Soil temperature is slightly higher than air temperature in a place. It influences life processes of soil biota including plants. Soil air is retained in soil pores; its composition is variable, and it contains higher carbon dioxide and moisture and lower oxygen concentration than atmospheric air. Soil air has a great role in respiration of plant roots and microorganisms and transformation of mineral and organic matter.