One form of irrigation commonly used for pasture grasses. Photograph: Bill Phillips
In the 1940s the average farmer could produce enough food for 19 people. Today, a farmer can produce enough food to feed 129 people. Technological advances have increased the productivity of farms, particularly by improving the ability to provide water to crops through irrigation. Irrigation is defined as the managed application of water to soil for the purpose of increasing crop production.
Irrigated agriculture has helped farmers produce an abundant and diverse supply of food, fibre and foliage products. Irrigation plays an especially important role in Australia where growing seasons are long but there is not enough rainfall to supply an optimum amount of water for commercial crops.
There are three main types of irrigation - surface gravity flow, pressurised sprinkler and micro-irrigation. In order to select the appropriate type of irrigation, the farmer must make informed decisions. Water availability, economics, soil types and plant biology factors must all be studied before choosing an irrigation technique.
Some of the major considerations for the irrigator include:
proximity of the field or pasture to a water source
adequate water distribution system to the paddock (pumps, canals or pipes)
amount of water required by the selected crop
quality of the available water
cost of the water
topography of the land
type of soil
amount of annual rainfall
the cost of irrigation supplies
then availability of labour to set-up and maintain the irrigation system
methods for recycling or handling excess irrigation water.
The complexity of choosing an appropriate irrigation system and using the available water to maximum efficiency has helped to ensure that good farmers are true water managers, very aware of conservation principles. It’s in their own best (economic) interest to use water wisely.
The method of irrigation can determine whether a crop can produce enough food or fibre to be economically viable. Water must be applied both at the right time and in the right volumes to be useful. This activity will provide students with an understanding of efficient water utilisation.
Boom spray irrigation
1. Divide the students into four groups, A through D. Give each group a description of their irrigation approaches and constraints (see below).
2. Then, give each student three cups filled with soil.
3. Each student is then given two bean seeds, two wheat grains, and two rice grains.
4. Have the students make a 1-2 cm deep hole in the soil in each cup and plant the seeds, each type to a single cup.
5. Have the students write their names and group number on their individual cups.
6. Assign each group a place for their cups indoors, where the plants can get plenty of light.
7. Provide each student with a Water Allocation Record Sheet (see below) to be filled in each time they ‘irrigate’.
8. Follow up 4-6 weeks: Students are likely will see a difference in growth and health of the plants as a result of these variations.
In a follow-up discussion students can compare the growing conditions for each group.
The micro-irrigation students
who undertake their assignment
conscientiously should see
the best results.