Agriculture:- Model Bankable Projects in India | Minor Irrigation : Sprinkler Irrigation Systems Chapter 1 --- www.nabard.org

Agriculture:- Model Bankable Projects in India | Minor Irrigation : Sprinkler Irrigation Systems Chapter 1 --- www.nabard.org

Chapter I

Requirements For Formulation of a Model Scheme By Banks

1.0       Introduction Water is a key factor in increasing agricultural production. About 78% of India's water resources are used for agriculture out of this only 50% is actually used by plants and the remaining water resources are wasted either as deep percolation or as evaporation. Excess irrigation not only reduces crop production and damages soil fertility but also causes ecological hazards like water logging and salinity. With competitive use of water and its increasing scarcity, it has become imperative to economize water use for optimum productivity. This is possible only through improved water management and adopting techniques of irrigation. One such method of modern irrigation is sprinkler irrigation system and is popular among the farmers across the country. Sprinkler irrigation system saves upto 50% of water compared to surface irrigation method and increases productivity by about 15-25 %. Until 1970, sprinkler irrigation system in India was used mostly in hilly area for plantation crops like tea and coffee. But thereafter it spread to other states like Haryana, Punjab, Rajasthan, MP, Maharashtra, U.P., Gujarat, Tamil Nadu, Karnataka, etc. where there was shortage of ground water for irrigation. Today farmers in almost all the States in the country have progressively adopted this system and it is estimated that about 10 million ha can be brought under sprinkler irrigation system in India. Realising the need for water use optimisation in the context of water scarcity and increasing agricultural productivity, the Government of India encourages large scale adoption of this method.  1.1      Sprinkler Irrigation System Sprinkler irrigation method distributes water to crops by spraying it over the crop area like a natural rainfall. The water under pressure flows through perforations or nozzles and sprays over the area. The pressure is provided by a pump of suitable capacity and horsepower. With careful selection of nozzle sizes, operating pressure and spacing, the actual water required for maintaining the soil moisture at field capacity is applied uniformly at a rate to suit the infiltration rate of soil thereby obtaining efficient water application. It is estimated that the sprinkler irrigation system substantially reduces the use of water and the crop productivity also increases.1.1.1    Suitability  The sprinkler irrigation system is a very suitable method for irrigation on uneven lands and on shallow soils. It is best suited to coarse sandy terrain where the percolation loss is more and where as a consequence, the frequency of irrigation required is more. The sprinkler irrigation system is also suitable in undulating terrain where land shaping is expensive or technically not feasible. The removal of fertile soil cover by land shaping is not advisable. Sprinkler irrigation system can also be adopted in hilly regions where plantation crops are grown. 1.1.2    Crops suitable  Nearly all crops are suitable for sprinkler irrigation system except crops like paddy, jute, etc. The dry crops, vegetables, flowering crops, orchards, plantation crops like tea, coffee are all suitable and can be irrigated through sprinklers. 1.1.3    Other advantages Fertilizers and pesticides can be effectively applied in split doses through sprinklers at little extra cost. This facilitates uniform fertilizer application and effective pest control. The overall cost of labour is generally reduced. Erosion of soil cover which is common in surface irrigation can be eliminated. 1.2       Type of Sprinkler Systems There are many types of Sprinkler systems available in the market. On the basis of the arrangement for spraying irrigation water, sprinkler systems are classified as: Rotating head system Perforated Pipe system Table-1 : Classification of rotating head sprinklers, their characteristics and adaptability

Type of sprinkler Gravity fed under tree sprinkler systems Normalunder tree sprinkler systems Permanent overhead systems Small overhead systems Low pressure systems Intermediate pressure systems High pressure systems Pressure range 0.7 to 1.0 kg/sq.cm. 1 to 2.5 kg/sq.cm. 3.5 to 4.5 kg/sq.cm. 2.5 to 4 kg/sq.cm. 1.5 to 2.5 kg/sq.cm. 2.5 to 5 kg/sq.cm 5 to 10 kg/sq.cm. Sprinkler discharge 0.06 to 0.25 li/sec. 0.06 to 0.25 li/sec. 0.2 to 0.6 li/sec. 0.6 to 2.0 li/sec. 0.3 to 1 li/sec. 2 to 10 li/sec. 10 to 50 li/sec. Diameter of nozzles 1 to 6 mm 1.5 to 6 mm 3 to 6 mm 6 to 10 mm 3 to 6 mm 10 to 20 mm 20 to mm Diameter of coverage 10 to 14 m 6 to 23 m 30 to 45 m 25 to 35 m 20 to 35 m 40 to 80 m 80 to 140 m Range of sprinkler spacing (square) -- -- 18 to 30 m 9 to 24 m 9 to 18 m 24 to 54 m 54 to 100 m Recommended speed of sprinkler rotations -- 0.5 to 1 rpm 1 rpm 0.67 to 1 rpm 0.5 to 1 rpm 0.7 rpm 0.5 rpm

1.3       Components of Sprinkler irrigation system Water source - open well / tube well / bore well / canal etc. Pumping unit - centrifugal, submersible Sprinkler - main and lateral pipe lines, riser pipe, sprinklers (nozzles) Other minor accessories / fittings like reducers, elbows, valve opening tees, end tees, regulators and gauges, valves, filters, etc. Fertilizer applicator The selection of pump, pipe line, dia, length, number of sprinklers, their design depend upon soil, topography, climate, cropping pattern and command area.

1.3.1    Pumping Unit A pump is required to carry water from the source through the main line and laterals upto the sprinkler or nozzle from where it is sprayed and applied to the crops. In areas where the land topography allows to develop enough pressure at nozzle or sprinkler head under gravity a separate pump may not be necessary. But in most cases it is necessary to pump water and carry it under pressure through the system. The pump is normally a centrifugal pump or a submersible pump fitted with usual accessories. If the water is pumped from a well or a tube well, and the capacity and horse power of the existing pump is sufficient to provide the desired pressure at the nozzle or sprinkler head, a separate pump may not be necessary for the system. But, in case the existing pump is not sufficient to provide the required pressure for the sprinkler system, a separate booster pump has to be provided depending upon the field situation after taking into account frictional losses in the main, laterals and risers and nozzles. The pumps selected must be as prescribed under IS 10804(1994) standard. 1.3.2    Main Lines Main line pipe is either of HDPE or Aluminium conforming to BIS specification viz., IS 7092 for aluminum pipes and IS 14151 (with IS 7328) for HDPE pipes. In cases where a portable system is proposed lightweight aluminum pipes are used for main line. The main pipeline carries water from the pumping unit to the various parts of the field. Main line may be permanent or portable. Permanent main line is advantageous where field boundaries are fixed and where crops require full season irrigation. Portable main lines are more economical when a sprinkler system is used for different fields or let out on hire to other farmers. Main line pipes are often buried so that they do not come in way of other agricultural operations. 1.3..3   Lateral Lines Lateral lines carry water from the main line to sprinklers or nozzles. Lateral lines are usually of aluminium or HDPE pipes with quick couplings. Lateral pipes are normally available in 5m, 6m, 12m lengths. Each length has quick couplings. All couplings are provided rubber gaskets in female portion, which tightens the coupling and makes it, leak proof. Lateral pipes should be of good quality and must conform to the respective prescribed standards. Numbers of laterals on a main pipe line vary depending upon the crop geometry, water requirement of crop, area required to be wetted etc., so that the total frictional head losses are not very high as that would require a very high capacity pump.

1.3.4    Nozzle/Sprinkler Head Sprinkler heads are the most important component of the sprinkler system. Their operating characteristics under optimum water pressure and climatic conditions, mainly wind velocity, will determine their suitability and the efficiency of the system. Most agricultural sprinklers are the slow rotation type. They may range from small single nozzle sprinklers to multiple nozzle sprinklers that operate at high pressure. The combination of pressure and rotation results in the jet of water being thrown to a considerable distance.

1.3.5    Riser The riser pipe connects the rotating sprinkler head to the lateral. Usually the pipe diameter varies from 12 mm to 75 mm with standard pipe threads. Riser with height 10 cm for small sprinklers and 1 m on large sprinklers give best results. In orchard and other crops the riser length could be 4-5 m for tree sprinkling. Sprinkler should stand slightly away from the crop so that the foliage does not interrupt its jets. High risers should be avoided unless necessary except for crops like sugarcane, banana, maize where height of the plant is high. 1.3.6    Other Accessories Other accessories used in the sprinkler system are: Reducers : Where more than one pipe size is used on the sprinkler line, a reducer is necessary for coupling pipes of different diameters. However, it is recommended that same diameter pipes are used everywhere. Elbows : These are used at joints for changing the direction of water flow. It is also used for reducing the pipe size. Valve opening elbows are used which fit over the take off valves on the mainline and allow a lateral to be connected. End plug Tees : These are placed at the end of a line so that the water feeds into them and the run of each tee points directly across the line. Therefore, two branches could be attached 180 degrees from each other. Regulators and Gauges : These include pressure regulators installed below the sprinkler to keep a constant pressure applied to the sprinkler regardless of whether the pipeline is laid up slope or down slope. Flow regulators are installed to control the flow and pressure of water flowing in the sprinkler. Pressure gauges are used to know the pressure at the pumpset or at the sprinkler. It is desirable to install gauges on each lateral. Valves :Valves are used to control the flow of water. Screw type valves are common. Drain valves are needed at valley portion of the land. Other valves are conventional pressure relief valves, check valves, outlet valves, air relief valves etc. Filters :Sprinkler nozzles are prone to blockage if water carries silt or is saline. In order to stop entry of dirt, sand weed or other suspended material in water flowing through the system, it is necessary to install filters placed on suction side of the pump and at vulnerable places. 1.3.7    Fertilizer Applicator This device is used for fertilizer application through the system instead of direct application. Only soluble fertilizers can be applied this way. Phosphorous fertilizers are not readily soluble and hence not applied through the system. When the fertilizers are applied through the system it is desirable to operate the system for long time to wet the soil and plant foliage and then inject the fertilizer in the system.

Continue........... Click Here