Landscape planting can be irrigated in number of ways: basin, furrow, sprinkler, soaker, and drip.
The method used will depend on type of plantings, amount, quality, source of water, terrain; available funding ; and source of labor.
In order to save water & labor, most intensive landscape plantings are being developed with automatically controlled systems.
Irrigation systems have become an increasingly large part of landscape construction budgets.
OBJECTIVE:
To supply water in usable amounts to the root zone of the plants.
To accomplish this it is necessary to consider the soil conditions and the growth characteristics of the land.
INTRODUCTION:
SOIL CHARACTERISTICS:
Infiltration rate: Amount of water that can be absorbed by soil in one hour. Measured in inches per hour.
Field capacity: Volume of water a soil will hold after the natural force of gravity has drained off the excess moisture. Measured in inches.
PLANT CHARACTERISTICS:
The plant species to be irrigated must be evaluated to determine the amount of water necessary to sustain it during peak growth periods.
Evapo-transpiration rate: This is the amount of water given up by a plant as a result of normal evaporation and transpiration of plant.
Type of equipment to be used:
How fast can the water be applied?
This is determined by infiltration rate of soil.
How much water needs to be applied?This depends on evapo-transpiration rate of the plant species.
How often must water be applied?
This is determined by the field capacity of the soil and the percentage of available moisture.
The answers to these questions will directly determine the type of equipment that should be used and the kind of system.
METHODS OF IRRIGATION:
Flood irrigation:
In flood irrigation, a large amount of water is brought to the field and flows on the ground among the crops. In regions where water is abundant, flood irrigation is the cheapest method of irrigation and this low tech irrigation method is commonly used by societies in developing countries.
Advantages:
Simple & cheap method.
Very less labor required,
Flushes salt out of the soil.
Disadvantages:
Could be applied on flat lands only.
About 50% of the water is wasted and does not used by the crops (due to irrigation, transpiration & run-off).
Anaerobic environment created due to flooding thus creating low nitrogen soil.
Steps taken for maximum utilization of water:
Leveling of fields:
Flood irrigation uses gravity to transport water, and, since water flows downhill, it will miss a part of the field that is on a hill, even a small hill. Farmers are using leveling equipment, to scrap field flat before planting. That allows water to flow evenly throughout the fields.
Surge flooding:
Traditional flooding involved just releasing water onto a field. In using surge flooding, water is released at prearranged intervals, which reduces unwanted runoff.
Capture and reuse of runoff:
A large amount of flood-irrigation water is wasted because it runs off the edges and back of the fields. Farmers can capture the runoff in ponds and pump it back up to the front of the field where it is reused for the next cycle of irrigation.
2. Furrow irrigation:
Furrow irrigation is actually a type of flood irrigation in which the water poured on the field is directed to Flow, through narrow channels dug between the rows of crops, instead of distributing the water throughout the whole field evenly. The furrows must all have equal dimensions, in order to guarantee that the water is distributed evenly. Like flood irrigation, furrow irrigation is rather cheap in areas where water is inexpensive.
3. BASIN IRRIGATION:
A basin is a level area surrounded by a berm to hold water. Basins are well adapted to level areas for shrub and flower beds and trees where foot traffic is infrequent. Soil should slope away from the trunk of plants. Any pavement surrounding a basin should be at the same level or higher than the top of the berm to minimize washing of the mud onto the pavement.
4. SPRINKLER OR SPRAY IRRIGATION:
Spray irrigation is a more modern way of irrigating, but it also requires machinery. Large scale spray irrigation systems are in use on large farms today. These systems have a long tube fixed at one end to the water source, such as a well. Water flows through the tube and is shot out by a system of spray-guns.
Used on shrub, flower, and tree plantings.
Provides fairly uniform water distribution even on hilly terrains.
The rate of application may need to be slow on uneven areas to allow for penetration.
A common type of spray-irrigation system are the center-pivot systems. The center-pivot systems have a number of metal frames (on rolling wheels) that hold the water tube out into the fields. And there can be a very big water gun at the end of the tube. Electric motors move each frame in a big circle around the field (the tube is fixed at the water source at the center of the circle), squirting water.
Advantages:
Water is distributed uniformly even on hilly terrains.
Very less amount of water is wasted in comparison to flood irrigation. Labor cost is very low.
Keeps humidity higher.
Disadvantages:
Moisten mulches but does not wash or float it away.
May pack the surface of the bare soil & reduce infiltration.
Flowers & tall plants may be damaged by the force of water.
Frequent light sprinklings with saline water may cause an unsightly or even toxic buildup of salt.
Better spray irrigation:
By use of traditional spray irrigation, water basically is just shot through the air onto fields. In the dry and windy air a lot of the water sprayed evaporates or blows away before it hits the ground. Another method, where water is gently sprayed from a hanging pipe uses water more efficiently. This method increases irrigation efficiency from about 60 percent (traditional spray irrigation) to over 90 percent. Plus, less electricity is needed.
5. SOAKER IRRIGATION:
Soakers are used to apply water at slow rates.
Consists of canvas or porous plastic tubes, of hoses, or of plastic tubing with fine holes.
Useful in difficult-to-irrigate areas: across slopes; near long, narrow plantings; or in soils with low infiltration rates. Water distribution along the soaker often varies from one end to the other, but will usually be more uniform at higher rates (pressure).
6. DRIP IRRIGATION:
Drip irrigation is the most expensive method of irrigation, it is also the most advanced and efficient method in respect to effective water use.
Usually used to irrigate fruits and vegetables, this system consists of perforated pipes that are placed by rows of crops or buried along their root lines and emit water directly onto the crops that need it.
Drip irrigation saves water upto 90% over flood irrigation on sandy soil & around 20% over sprinkling on clay soil.
Water high in salts should be filtered before use since otherwise they may clog the emitters and create a local buildup of high salinity soil around the plants if the irrigation water contains soluble salts.
It permits irrigation on the steep banks, shallow soils, soils with slow infiltration rates, and sandy soils.
Water wastage through evaporation from soil & weeds is also reduced.
7. PITCHER IRRIGATION:
Used in arid or semi-arid climatic
Pitcher irrigation uses unglazed clay pots to distribute water by diffusion and capillary action through the wall of the clay pot. Pitchers are less expensive per acre and much more effective than traditional means.
Per cubic meter of water, the buried clay pot method can produce 2.5 to 6 kilograms of total plant yield, compared to 1.4 kg with drip irrigation, 0.9 kg with sprinklers, and 0.7 kg in furrow irrigation systems.
ADVANTAGES:
save over 90% of water over traditional irrigation methods
CHEAP!
easy to install, operate and maintain
controls weeds
Minimize erosion by keeping the water underground
implement as much or as little as needed
DISADVANTAGES:
However, as with any system, pitcher irrigation is not a perfect solution. There is a dramatic disadvantage of plants becoming dependent on the pitchers for their only water source and therefore do not develop the deep-rooting systems that would develop otherwise.
Labor required for regular checking of pots.
Too expensive for large areas.
Great Article.
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