Agriculture Engineering-chptr12 irrigation
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  • 1. IRRIGATION
  • 2. Why is irrigation important• Not much new land waiting to be opened up for agriculture. The main increase in food supplies has to come from making better use of land already farmed• More efficient crop production will help e.g. better varieties, more use of fertilizer, mechanization, etc. but rainfall is still a limiting factor for a very large proportion of the earth’s surface and so irrigation is important in increasing production• With irrigation, crop yields may be made more reliable, or two crop a year may be possible instead of one
  • 3. Advantages of Irrigation1. To supply moisture which allows plant growth where there was none before, or to get better growth, or to extend the growing season2. An insurance against drought3. To allow the movement of plant nutrients. The chemicals for plant growth are absorbed by the plant in solutions eg surface application of nitrogenous fertilizer will have no effect on a completely dry soil. There must be water to dissolve it and take it down to the roots4. To leach undesirable salts, that is to wash them out in solution5. To control the environment for growing plants. Eg prevent frosts, to keep plant cool or to keep them moist
  • 4. Limitations1. Salinity a. The water table is raised by irrigation, salts will build up into the root zone b. Water containing dissolved salts for irrigation In both cases, water is transpired by the plants and evaporated from the soil surface but the salts remain behind so there is a progressive buildup over the years.2. Water logging Too much water applied or inadequate drainage Seepage from a canal3. Erosion and sedimentation Water flowing too fast in furrows or canals will cause soil erosion Deposition of silt in canals is also undesirable4. Damage to soil structure Some kinds of sprinkler irrigation can damage the soil through erosive application rates
  • 5. Sprinkler IrrigationAdvantages:1. Leveling is not required, so sprinkler can be used on hilly or uneven land2. Light, frequent watering are possible3. Uniform distribution of water is possible4. Amount of water can be easily controlled5. No permanent field obstacles such as ditches6. Small in-flow of water into the system can be used7. The equipment can be mobile, and this is a vital requirement for supplementary irrigation8. The system is easy to set up
  • 6. Disadvantages:1. The capital cost of pumps, pipes and equipment is high2. It needs a high power pump and a high flow rate of water3. The size of droplet of water is not suitable for certain crops esp. vegetables4. The efficiency will be reduced by strong winds5. Weed control will be affected
  • 7. Types of Sprinklers and Sprays1. Reaction rotation sprinkler Most often used for lawns The rotating head is driven around by the reaction of the jets at the end of 2 or 4 arms It is cheap but has little field application2. Fixed head sprays Used for lawns and orchard The vertical jet strikes downward pointing cone and is spread out in a flat cone spray It is robust and no moving parts but gives a poor distribution
  • 8. 3. Perforated pipe Light weight aluminum piping has many very small holes drilled in the top of the pipe so that fine jets come out at different angles and wet an area on either side Droplet size is small but the rate of application is higher4. Slow rotation sprinkler or Rain gun Mostly used in field installations Most sprinkler have either a single nozzle or two opposing nozzles 2 Nozzles - One spray the inner area, the other called the distance jet, extend the diameter of application The nozzles are interchangeable and available in different sizes to suit different pressures
  • 9. Design of Sprinkler System3 factors are interrelated and must be taken into account whendesigning the system:a. Soil factor Moisture Holding Capacity (MHC, in/ft) Coarse texture – low MHC Fine texture – high MHC Water infiltration rate (in/hr) Coarse texture – high value Fine texture – low valueb. Crop factor Depth of root zone (inch)c. Weather factor Rate of Potential Evaporation (PET) Hot weather – high PET Cold weather – low PET
  • 10. Drip Irrigationis the frequent, slow application of water tothe soil for the purpose of sustaining plantgrowththis is done through mechanical devices calledemitter that are located at selected point alongwater delivery linesMost emitter are placed on the soil surface, butthey can be buried at shallow depth forprotectionNumber of emitters depending on the size ofthe plant, ranges from one to eight or more forlarge trees
  • 11. Advantages1. Energy conservation - Operating pressures are lower compared to sprinkler thus saving pumping energy2. Water conservation - the volume of water wetted by drip irrigation is usually less than that of other irrigation methods because between vegetative growth is root irrigated - important that approx. 33% of the soil in the wet zone is wetted3. Additional vegetative growth - when soil moisture is maintained at a high level with drip irrigation, there is a noticeable increase in growth of plant
  • 12. 4. Fertilizer efficiency - areas of low rainfall, drip system are an effective means of getting fertilizer into the soil moisture where it can be utilized by the plants - greater control over fertilizer placement and timing through the system may lead to improved fertilizer efficiency5. Low labour requirements - the low application rates allow large areas to be irrigated at one time for a given capacity of pump by opening and closing the valves for each irrigation block
  • 13. LimitationEmitter clogging - Because the water outlets or orifice in most emitters are very small, they are easily become plugged by particles of mineral and organic matter
  • 14. Filter- one of the component of the whole system of irrigation. It is used to prevent foreign particles such as soil, sand and debris to move together with the water in the pipe line and thereby causing clogging of the emitters
  • 15. Types of Filters 1. Screen or mesh (100 mesh filters) 2. Grooved disc 3. Sand media - for polluted pond or water Filters are usually placed after the pump outlet and it can be dismantled to clean the screen or grooved while sand media can be cleaned by back washingEmitters- used to transmit and regulate the amount of water needed by the plant through effective root zone- discharged rate of emitter varies from 0.5, 1.0, 2.0 and 4.0 liter per hour
  • 16. Water PumpsMost commonly used is a centrifugal type pump,operated by diesel engine or an electric motorSize of the engine and pumps depends on the totalhorsepower requirement of the systemIf the total HP requirement is too high, divide thesystem into 2 or more blocks of irrigation, andirrigate one block at a time so that horsepowerrequirement is reduced accordingly. This mayreduced the pump size and also the cost of havingthe pump unit.
  • 17. Piping System1) Main, sub-main and lateral pipe lines2) PVC is commonly used as the main and sub-main lines3) The latest technology is using High Density Polyethylene (HDPE) Tubing which can withstand high pressure, non-corrosive and durable4) The sizes of main and sub-main depend on the discharge of water in the system. The common size is between 20mm – 630mm (outside diameter)5) Low Density Polyethylene Tubing (LDPE) of diameter between 13mm to 25mm is used for lateral lines. Recommended discharge rate for 13mm diameter LDPE is 1.0 gph
  • 18. THANK YOU