Irrigation methods.ppt - CHAPTER THREE IRRIGATION METHODS...

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CHAPTER THREE: IRRIGATION CHAPTER THREE: IRRIGATION METHODS AND DESIGNS METHODS AND DESIGNS 3.1 IRRIGATION METHODS a) Surface Irrigation: Just flooding water. About 90% of the irrigated areas in the world are by this method. b) Sprinkler Irrigation: Applying water under pressure. About 5 % of the irrigated areas are by this method. c) Drip or Trickle Irrigation: Applying water slowly to the soil ideally at the same rate with crop consumption. d) Sub-Surface Irrigation: Flooding water underground and allowing it to come up by capillarity to crop roots.
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3.2 SURFACE IRRIGATION 3.2 SURFACE IRRIGATION Water is applied to the field in either the controlled or uncontrolled manner. Controlled: Water is applied from the head ditch and guided by corrugations, furrows, borders, or ridges. Uncontrolled: Wild flooding. Surface irrigation is entirely practised where water is abundant. The low initial cost of development is later offset by high labour cost of applying water. There are deep percolation, runoff and drainage problems
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3.2.1 Furrow Irrigation 3.2.1 Furrow Irrigation In furrow irrigation, only a part of the land surface (the furrow) is wetted thus minimizing evaporation loss. Furrow irrigation is adapted for row crops like corn, banana, tobacco, and cabbage. It is also good for grains. Irrigation can be by corrugation using small irrigation streams. Furrow irrigation is adapted for irrigating on various slopes except on steep ones because of erosion and bank overflow.
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Furrow Irrigation Contd. Furrow Irrigation Contd. There are different ways of applying water to the furrow. As shown in Fig. 3.1, siphons are used to divert water from the head ditch to the furrows. There can also be direct gravity flow whereby water is delivered from the head ditch to the furrows by cutting the ridge or levee separating the head ditch and the furrows (see diagram from Gumb's book). Gated pipes can also be used. Large portable pipe(up to 450 mm) with gate openings spaced to deliver water to the furrows are used. Water is pumped from the water source in closed conduits. The openings of the gated pipe can be regulated to control the discharge rate into the furrows.
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Furrow Irrigation by Cutting Furrow Irrigation by Cutting the Ridge the Ridge
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Furrow Irrigation with Siphons Furrow Irrigation with Siphons
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Fig. 3.1: A Furrow System Fig. 3.1: A Furrow System
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3.2.1.1 Design Parameters of 3.2.1.1 Design Parameters of Furrow Irrigation Furrow Irrigation The Major Design Considerations in Surface Irrigation Include: Storing the Readily Available Moisture in the Root Zone, if Possible; Obtaining As Uniform Water Application As Possible; Minimizing Soil Erosion by Applying Non-erosive Streams; Minimizing Runoff at the End of the Furrow by Using a Re-use System or a Cut -Back Stream; Minimizing Labour Requirements by Having Good Land Preparation, Good Design and Experienced Labour and Facilitating Use of Machinery for Land Preparation, Cultivation, Furrowing, Harvesting Etc.
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Furrow Irrigation Contd.
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