Soils and Irrigation

1. Understanding soils (SO1 - 0801)

  Soil consists of five main components:

• air

• water

• organic matter

• mineral solids (sand, silt and clay)

• living plants and animals

The air and water components make up the spaces or soil pores. These pores allow water to be stored and moved from one place to another in the soil.

The ability of water to move or be stored depends on the amount of each of the soil mineral solids present (soil texture) and the way they are arranged together (soil structure).

Soil Texture:

The relative proportion of sand, silt and clay present in a soil is known as the soil texture.

 Texture will influence the movement of water through the soil, how much water can be stored in the soil and how much of the stored water is available to plants.

In irrigation terms, texture will determine the rate at which water should be applied, how much should be applied and how often irrigation should occur.

Soil Structure:

Structure of a soil is the way the soil particles are grouped together to form a soil crumb or ‘ped’.

Organic matter will aid in providing good soil structure because it acts likes a glue, binding soil particles together.

Good structure allows for improved infiltration and drainage. It also enhances root growth. This provides the plant with the ability to access a greater amount of water and nutrients.

While soil texture remains constant, soil structure can be lost through destructive tillage practices. Poor soil structure will mean irrigations become more difficult to manage.

The Rural Water Use Efficiency Initiative is a joint venture between BSES, CANEGROWERS and the Queensland Government through the Department of Natural Resources and Mines. For more information, please ring your local Rural Water Use Efficiency Officer.