First year undergraduate students in agricultural engineering are normally introduced into the discipline through a core unit which deals with fundamental concepts in agriculture and agro-meteorology. One important concept that they have to understand before proceeding to higher levels is about how much water plants need to survive in varying climatic and soil
conditions. Accordingly, two terms relating to water movement and loss in the growing environment are commonly discussed.
These are infiltration and evapotranspiration, respectively. Infiltration is a term used to describe the movement of water into the soil. Different types of soils have different rates of infiltration. For instance, sandy soils have faster infiltration rate than clay soils into which water movement is very slow.
Infiltration on its own is less important if not connected to the water holding capacity of a particular soil. The water holding capacity is the maximum amount of moisture that the soil can hold without causing runoff. Knowledge of infiltration and water holding capacity gives an idea on how much and how long to irrigate.