Drip irrigation is sometimes called trickle irrigation and involves dripping water onto the soil at very low rates (2-20 litres/hour) from a system of small diameter plastic pipes fitted with outlets called emitters or drippers. Water is applied close to plants so that only part of the soil in which the roots grow is wetted, unlike surface and sprinkler irrigation, which involves wetting the whole soil profile. With drip irrigation water, applications are more frequent (usually every 1-3 days) than with other methods and this provides a very favorable high moisture level in the soil in which plants can flourish.
It is best suited to areas where water quality is marginal, land is steeply sloping or undulating and of poor quality, where water or labour are expensive, or where high value crops require frequent water applications.
The suitability of the various irrigation methods, i.e. surface, sprinkler or drip irrigation, depends mainly on the following factors:
– Natural conditions
– type of crop
– type of technology
– previous experience with irrigation
– required labour inputs
– costs and benefits.
How does drip irrigation work?
Water and nutrients are delivered across the field in pipes called ‘dripperlines’ featuring smaller units known as ‘drippers’. Each dripper emits drops containing water and fertilizers, resulting in the uniform application of water and nutrients direct to each plant’s root zone, across an entire field.
For busy gardeners, the main benefit of using a drip irrigation system is the savings of both time and effort. Drip irrigation systems eliminate the need to drag around hoses and sprinklers. You place your soaker hoses once, and leave them be. For drip irrigation systems that use a timer, gardeners need only spend a few seconds to turn the system on; the timer automatically turns it off.
The two main types of drip irrigation are:
- Surface drip irrigation – The water is delivered to the surface of the soil directly above the root system of the plants. This particular type of drip irrigation is mainly used on high-value crops.
- Subsurface drip irrigation – The water is applied directly to the root system. This type is used particularly in growing row crops
Drip irrigation is most suitable for row crops (vegetables, soft fruit), tree and vine crops where one or more emitters can be provided for each plant. Generally only high value crops are considered because of the high capital costs of installing a drip system.
Drip irrigation is adaptable to any farm-able slope. Normally the crop would be planted along contour lines and the water supply pipes (laterals) would be laid along the contour also. This is done to minimize changes in emitter discharge as a result of land elevation changes.
Drip irrigation is suitable for most soils. On clay soils water must be applied slowly to avoid surface water ponding and runoff. On sandy soils higher emitter discharge rates will be needed to ensure adequate lateral wetting of the soil.
Suitable irrigation water
One of the main problems with drip irrigation is blockage of the emitters. All emitters have very small waterways ranging from 0.2-2.0 mm in diameter and these can become blocked if the water is not clean. Thus it is essential for irrigation water to be free of sediments. If this is not so then filtration of the irrigation water will be needed.
Blockage may also occur if the water contains algae, fertilizer deposits and dissolved chemicals which precipitate such as calcium and iron. Filtration may remove some of the materials but the problem may be complex to solve and requires an experienced engineer or consultation with the equipment dealer.
Drip irrigation is particularly suitable for water of poor quality (saline water). Dripping water to individual plants also means that the method can be very efficient in water use. For this reason it is most suitable when water is scarce.
Advantages and Disadvantages of Drip Irrigation
Advantages of Drip Irrigation:
- Maximum use of available water.
2. No water being available to weeds.
3. Maximum crop yield.
4. High efficiency in the use of fertilizers.
5. Less weed growth and restricts population of potential hosts.
6. Low labour and relatively low operation cost.
7. No soil erosion.
8. Improved infiltration in soil of low intake.
9. Ready adjustment to sophisticated automatic control.
10. No runoff of fertilizers into ground water.
11. Less evaporation losses of water as compared to surface irrigation.
12. Improves seed germination.
13. Decreased to tillage operations
Disadvantages of Drip Irrigation
- Initial cost is high.
- May cause clogging if water is not filtered correctly.
- Problems in moisture distribution.
- Salinity problem.