Soil moisture stress

• It is the sum of soil moisture tension and osmotic pressure of soil solution. Salt in the soil increased the force needed to extract water and that tension caused by salt is osmotic pressure.
• So, in general plant growth is a function of both soil moisture tension and as well as osmotic pressure.

Soil moisture characteristics

• The field capacity, permanent wilting point (PWP) and available water content are called the soil moisture characteristics.
• They are constant for a given soil, but vary widely from one type of soil to another.
• In general, amount of water available to plant, infiltration, percolation, amount of irrigation etc. can be predicted with the help of soil moisture characteristic curve of that soil.
• Soil moisture characteristic curve of clay, loamy and sandy soil is as below and from this we can analyze many things by observing the nature of graph.

Soil moisture constant

• It is the imaginary boundary of the soil moisture available to the plants showing the significance of different soil moisture level on the plant bodies.
• Under field conditions, water content of soil is always changing constantly with time and depth of soil and is not static or constant. However, the concept of soil moisture constants greatly facilitates in taking decision in irrigation.