ABSTRACT
The physical nature of soil affects the variations of temperature with depth and time of day and season known as the thermal regime. Soil depth may be terminated abruptly by a rock surface which places a permanent obstruction to the downward-growing roots. Circumstances can arise when there is a temporary high water table in the soil in local areas, where a subsoil layer of an impermeable nature prevents the rapid deep seepage of water after a period of heavy rainfall. The workability of the soil is a problem which differs in nature and extent according to whether animals or machine power are used to draw the implements across the soil. Soil texture is a factor to be taken into account in the planning of crop rotations, often thought to be only a question of soil fertility. Soil temperatures at seed level or around the main plant roots are very important environmental factors in plant growth, especially in the initial stages.
