Irrigation is the artificial application of water to the soil usually for assisting in growing crops. Agriculture that relies only on direct rainfall is referred to as rain-fed farming.
Sources of irrigation water can be groundwater extracted from springs or by using wells, surface water withdrawn from rivers or dams, or non-conventional sources like treated wastewater, desalinated water or drainage water.
Irrigation systems typically being used in South Africa today include:
- Flood irrigation
- Draglines, quick-coupling lines
- Micro irrigation
- Drip irrigation
These irrigation systems can be defined under the following types:
- Static (micro and sprinkle) – these systems remain static while water is applied.
- Moveable (quick coupling; dragline; hop-along; big gun; rotating boom) – these remain static during irrigation but are moved, manually or mechanically, between irrigations.
- Moving (centre pivot; linear and travelling irrigator), which move by themselves during irrigation.
- Flood (basin; border; furrow; short furrow) - water flows over the soil surface for spreading and infiltration purposes.
Irrigated agriculture plays an important role in stabilising the production of food and eventual food security. Although it uses 60% of the available water in South Africa, it does not do so at the expense or the detriment of any other sector of the economy. Yet no farmer would disagree that the demand on our scarce water resources makes the efficient use of all water in South Africa a necessity.
Source: adapted from a letter written by Johannes Möller, at the time of being president of Agri SA, to the Minister of the Department of Water Affairs
Source: http://en.wikipedia.org/wiki/Irrigation (adapted); “Irrigation Basics", an article by Johannes Maree (contact him at johannesmaree [at] absamail.co.za)
2. Commercial Farmer Points of Interest
Computer Software for Farmers
Irrigation scheduling is defined as the correct amount of water being applied to a crop at the correct time. We have only a limited resource of water, which should be utilised in the most efficient way possible. By optimising scheduling principles we can:
- Prevent over and under watering
- Facilitate crop manipulation
- Prevent unnecessary crop stress
- Create ideal air-water balance
- Manage soil water buffer
- Optimise salinity management
- Prevent soil compaction
- Save on energy costs
- Promote root development
- Improve fertiliser uptake
- Maximise harvest potential
Water legislation means that a farmer has to budget for how much water will be used. By using scheduling software the farmer can tell exactly how much water he used so that he can estimate how much he’s going to need for the next year as required. Some software companies have addressed the new regulations by developing software solutions that can successfully keep track of water budgeting information and spray records.
One module uses climate and soil moisture information to generate irrigation recommendations. It will also help predict water requirements. By loading this information, you will be able to make use of a second module which controls the irrigation in the field. This module also can determine when to irrigate in order to prevent frost or to cool down the plants by keeping track of temperature readings. By means of radio or of wired links, the pumps and valves in the field are controlled.
Source: DFM Software
Precision irrigation means that land can be differentially irrigated according to variations in soil type, topography, soil-water capacity, yield potential. Accepting these differences (and irrigating according to them) translates into less wastage of water and fertiliser.
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