About Drip Irrigation System
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 favourable high moisture level in the soil in which plants can flourish.
Drip irrigation system delivers water to the crop using a network of mainlines, sub-mains and lateral lines with emission points spaced along their lengths. Each dripper/emitter, orifice supplies a measured, precisely controlled uniform application of water, nutrients, and other required growth substances directly into the root zone of the plant.
Water and nutrients enter the soil from the emitters, moving into the root zone of the plants through the combined forces of gravity and capillary. In this way, the plant’s withdrawal of moisture and nutrients are replenished almost immediately, ensuring that the plant never suffers from water stress, thus enhancing quality, its ability to achieve optimum growth and high yield.
Drip System Layout
- Pump station
- By-pass assembly
- Control valves
- Filtration system
- Fertilizer tank /Venturi
- Pressure gauge
- Mains / Sub-mains
- Emitting devices
- Micro tubes
Pump station takes water from the source and provides the right pressure for delivery into the pipe system.
Control valves control the discharge and pressure in the entire system.
Filtration system cleans the water. Common types of filter include screen filters and graded sand filters which remove fine material suspended in the water.
Fertilizer tank/venturi slowly add a measured dose of fertilizer into the water during irrigation. This is one of the major advantages of drip irrigation over other methods.
Mainlines, submains and laterals supply water from the control head into the fields. They are usually made from PVC or polyethylene hose and should be buried below ground because they easily degrade when exposed to direct solar radiation. Lateral pipes are usually 13-32 mm diameter.
Emitters or drippers are devices used to control the discharge of water from the lateral to the plants. They are usually spaced more than 1 metre apart with one or more emitters used for a single plant such as a tree. For row crops more closely spaced emitters may be used to wet a strip of soil. Many different emitter designs have been produced in recent years. The basis of design is to produce an emitter which will provide a specified constant discharge which does not vary much with pressure changes, and does not block easily.
Wetting Pattern In Drip Irrigation
Unlike surface and sprinkler irrigation, drip irrigation only wets part of the soil root zone. This may be as, low as 30% of the volume of soil wetted by the other methods. The wetting patterns which develop from dripping water onto the soil depend on discharge and soil type. Figure 64 shows the effect of changes in discharge on two different soil types, namely sand and clay.
Wetting pattern in Sandy Soils
Wetting pattern in Clay Soils
Although only part of the root zone is wetted it is still important to meet the full water needs of the crop. It is sometimes thought that drip irrigation saves water by reducing the amount used by the crop. This is not true. Crop water use is not changed by the method of applying water. Crops just require the right amount for good growth.
The water savings that can be made using drip irrigation are the reductions in deep percolation, in surface runoff and in evaporation from the soil. These savings, it must be remembered, depend as much on the user of the equipment as on the equipment itself.
Drip irrigation is not a substitute for other proven methods of irrigation. It is just another way of applying water. 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.
Crops Suitable for Drip Irrigation System
|1.||Orchard Crops||Grapes, Banana, Pomegranate, Orange,
Citrus, Mango, Lemon, Custard Apple, Sapota,
Guava, Pineapple, Coconut, Cashewnut,
Papaya, Aonla, Litchi, Watermelon,
|2.||Vegetables||Tomato, Chilly, Capsicum, Cabbage,
Cauliflower, Onion, Okra, Brinjal, Bitter Gourd,
Ridge Gourd, Cucumber, Peas, Spinach,
|3.||Cash Crops||Sugarcane, Cotton. Arecanut, Strawberry etc.|
|4.||Flowers||Rose, Carnation, Gerbera, Anthurium,
Orchids, Jasmine, Dahilia, Marigold etc.
|5.||Plantation||Tea, Rubber, Coffee, Coconut etc.|
|6.||Spices||Turmeric, Cloves, Mint etc,|
|7.||Oil Seed||Sunflower, Oil palm, Groundnut etc.|
|8.||Forest Crops||Teakwood, Bamboo etc.|
Response of different crops to Drip Irrigation System
|Crops||Water saving (%)||Increase in yield (%)|
Benefits of Drip Irrigation
- Increase in yield up to 230 %.
- Saves water up to 70% compare to flood irrigation. More land can be irrigated with the water thus saved.
- Crop grows consistently, healthier and matures fast.
- Early maturity results in higher and faster returns on investment.
- Fertilizer use efficiency increases by 30%.
- Cost of fertilizers, inter-culturing and labour use gets reduced.
- Fertilizer and Chemical Treatment can be given through Micro Irrigation System itself.
- Undulating terrains, Saline, Water logged, Sandy & Hilly lands can also be brought under productive cultivation.
Water Conservation Through Drip
Water is conserved in the following ways:
- Drip irrigation application uniformity is very high, usually over 90%.
- Unlike sprinklers, drip irrigation applies water directly to the soil, eliminating water loss from wind.
- Application rates are low so water may be spoon fed to the crop or plant root zone in the exact amounts required (even on a daily or hourly basis). In contrast, other methods entail higher water application quantities and less frequency. If young plants need water frequently, much of the water applied is often wasted to deep percolation or runoff.
- Low application rates are less likely to run off from heavier soils or sloping terrain.
- Drip irrigation does not water non-targeted areas such as furrows and roads in agriculture, between beds, blocks or benches in greenhouses, or hardscape, buildings or roads in landscape.
- Drip irrigation easily adapts to odd-shaped planting areas which are difficult to address with sprinklers or gravity irrigation.
- Drip irrigation is capable of germinating seeds and setting transplants which eliminates the need for “sprinklering up” and eliminates the resulting waste in the early stages of crop growth.
Drip irrigation is today’s need because Water – nature’s gift to mankind is not unlimited and free forever. World water resources are fast diminishing.