IUCN Pakistan. Efficient Irrigation Systems

Transcription

1 IUCN Pakistan Efficient Irrigation Systems

2 Background Pakistan»s agriculture is classified as irrigated agriculture with about 18 million hectares (Mha) of irrigated area contributing 90% of total agricultural produce. The area with potential for agricultural production, if water is made available is 26 Mha. Despite enormous losses in the irrigation system and reduced supplies due to prolonged drought and reduced river flow, the farmers are still using highly inefficient and obsolete methods of irrigation. Irrigation practices followed in the Balochistan Province are primitive and highly inefficient. Orchards and Fruit Farms in particular are irrigated by flooding entire fields, which reduces water use efficiency to less than 40 percent from water source to crop use. There is immense need to save water due to severe water crisis being faced by the country. Modern irrigation technologies for field crops and orchards can help increase water use efficiencies to 90%. Though capital intensive, the future of irrigated agriculture in the province depends on adopting these technologies for crop production as water is becoming an ever-increasing hard-to-get resource and the gap between demand and supply widens. The following sections give brief description of different efficient systems/technologies popular in other parts of the world and which could be propagated in Pakistan in general and Balochistan in particular. Trickle System Trickle system is basically a frequent, slow application of water either directly onto the land surface or into the root zone of the crop through mechanical devices called emitters or applicators located at selected points along with the water delivery lines. It is based on the fundamental concept of irrigating only the root zone of the crop rather than the entire land surface and maintaining the water content of the root zone at near optimum levels. The uniformity of application is not affected by wind because the water is applied at or below the ground 2

3 surface. A well-designed and maintained drip irrigation system is capable of achieving an application efficiency of 90 percent. Generally it is suitable for row crops or for growing new orchards. Trickle Irrigation for trees Types of Trickle Irrigation There are two types of trickle irrigation systems that can be installed. These are: i) On-surface drip It is the slow, nearly continuous application of water as discrete drops. It is most suitable for new plantation or very young trees in the orchards. ii) Sub-surface drip It involves the use of point and line source emitter to apply water below the soil surface. It is most suitable for shallow rooted crops like vegetables, strawberries etc. Discharge rate is generally the same as in drip irrigation. Advantages The depth of water penetrating in the root zone can be improved appreciably. 3

4 Trickle Irrigation on flower beds Water saving is achieved by low application rate, reducing the total evaporative surface, reducing run off, and controlling deep percolation Greater weed control and improved quality of crops through direct fertilizer application and meeting exact crop water requirements Dry soil between crop rows makes cultural operations and labor movements easier Fertilizer can be injected in the irrigation water Use of saline water is possible because irrigations are frequent and salts are diluted Requires low energy requirements while achieving fairly high application uniformity Bacteria, Fungi, pest and diseases that depend on moist environment are reduced Applicable to all types and topography Minimum labor requirements to maintain and operate the system. Disadvantages Clogging of system components by physical, chemical and biological factors 4

5 Crop root development is normally limited to the wetted portion of the root zone, which reduces the plant»s stability to withstand winds Not economical for high plant density crops Excess salts may accumulate at the soil surface and towards the fringes of the wetted soil System Costs Trickle systems are generally considered capital intensive. However they have a long life in some cases exceeding 20 years with high quality component materials. The per land unit cost of the systems is highly variable and depends on the land area to be brought under trickle system, the type of crop, and the spacing between plants. Typically, in Pakistan, the cost varies from Rs. 60,000 to 80,000 per hectare for systems installed with imported components. For systems laid with local components the cost may reduce to 40,000 to 60,000 per hectare. System Component Materials The main components of the system are: main and lateral pipes (PVC), fertilizer tank/injector (Aluminium or GI), pump, tricklers/drippers (PVC), and system control assembly (GI) and is locally available. Bubbler Irrigation This system is a modified version of trickle irrigation system. In this method water is applied to the land surface as a small stream by tubular shaped bubblers that are attached to a buried or on the surface lateral line. The system is suitable for growing orchards (particularly for trees over two years of age). Water is delivered at or near the root zone of plants in small basins around the trunks of the trees to cover the root zone. Efficiency is achieved through minimizing evaporation and deep percolation losses and eliminating runoff. Generally discharge rate variations from bubblers due to system head losses and unevenness in land topography 5

6 can be easily reduced with the help of a screwdriver. Deep percolation, where water moves below the root zone, can occur if a bubblers system is operated for too long a duration. On the other hand operating the system with short duration can cause deficit irrigation. Distribution can be adjusted for uniformity throughout a field or for precise water delivery to individual plants based on calculation of the moisture holding capacity of the root zone and the daily irrigation requirements of the crop. Bubbler systems consisting of bubblers, pipes, valves, trenches, and basins, etc. require routine maintenance, which is not very technical. Advantages of Bubbler Systems Bubblers are visible and problems are noticeable Bubblers require minimal filtration Bubbler flow rate and wetted area are easy to adjust Bubblers are durable and require little maintenance Depth of water penetration in the root zone is improved appreciably The system allows better weed control The soil between trees remains dry to allow easy cultural and harvesting operations Bubbler System cup formed by water spray 6

7 Bubbler System inverted shower Fertilizer can be mixed with irrigation water for directly reaching root zone to improve crop yields and quality Use of saline water becomes possible due to dilution effect through frequent application of water Energy requirements to operate the system are low at psi Growth of bacteria, fungi, pests that thrive in moist environment is reduced due to drier conditions around the plant Uniformity of application is relatively high and the system can be laid for all topographic conditions The system requires minimal labor requirements to operate and maintain. System Costs Bubbler irrigation is basically just a slight modification over trickle systems and as such the costs of these systems and materials are similar to drip systems. Sprinkler System Sprinkler is a unique irrigation system. It is designed to ensure maximum water saving, affordability and ease of installation. Sprinkler irrigation systems are usually more 7

8 Sprinkler at work efficient than flood irrigation systems and provide efficient coverage for small to large areas. The system can save water by about 35 to 40 percent when compared with flood irrigation method. In sprinkle irrigation system, rainfall like conditions are created by spraying water into the air through a sprinkler nozzle and allowed to fall on the land surface in a uniform pattern. Water to the nozzles heads is delivered through a system of pipes usually by pumping. It is then sprayed into the air to wet the entire soil surface through spray heads so that it breaks up into small water drops, which fall to the ground. There are various types of sprinkler systems available to suit various kinds of physical, climatic, soil, and crop conditions. These include sprayers, centre pivot, mobile, rain-gun systems, etc. The systems is also adaptable to nearly all irrigable soils since sprinklers are available in a wide range of discharge capacity and allocation rates. On an average, agricultural sprinkler systems are about 60 percent efficient. They are more susceptible to wind than flood systems are, and can have much lower efficiencies in windy conditions. The systems are suitable for almost all field crops like wheat, gram, pulses as well as vegetables, cotton, soybean, tea, coffee, tobacco, sugarcane, and other fodder crops and can be installed in residential and industrial units, hotels, resorts, public & government enterprises, playgrounds, and race courses. In recent years the systems are being increasingly used for fire fighting, as 8

9 they can be programmed to automatically operate inside building whenever a fire alarm goes off. Advantages of sprinkle System System losses (runoff, seepage) substantially reduced Over irrigation is completely eliminated and uniformity of application is high Irrigation water requirements reduced as compared to other methods No land levelling required in the field and land use for productive purposes can be maximized Fertilizer can be injected in the irrigation water to reach the root zone directly The system allows better weed control Limitations of sprinkle System Poor uniformity and application efficiency in high wind regimes and/or dry and hot conditions Capital cost is high with greater operational costs due to higher energy requirements Not suitable for paddy crops Crops prone to diseases due to moist environment Rain Gun sprinkler 9

10 Water with impurities and sediments may damage the system Cost of Sprinkler Irrigation Systems As for trickle irrigation, the cost of these systems is highly variable and depends on the selected system type. A simple rain-gun would cost around Rs. 30,000 and can be used to irrigate over 25 acres under a rotational system. Centre pivots are meant for very large farms and may cost Rs. 5 million for a moderate sized system to irrigate 20 ha of cropped area in one go. Pop-up systems used for irrigating lawns are relatively cheaper and cost about Rs. 50,000 per ha. As the systems operate under high heads, the pumping costs are high. Bed and Furrow Irrigation In Pakistan basin irrigation is the most widely used practice for irrigating field crops. The application efficiency of such systems is generally very low due to deep percolation losses, field undulations, un-compatible intake discharges, and run-off losses. Improving and developing crops specific field layouts can reduce the losses. Bed and furrow irrigation system for field crops can help save water to a great extent. Bed and Furrow Method for Vegetable 10

11 Bed and Furrow Method plants on beds In the bed and furrow method, water is applied only in furrows. Experiments have proved that cotton grown on bed and furrow system had the maximum water use efficiency and yield against other methods of irrigation. Water saved in bed and furrow irrigation can be used to increase the cropping intensity and also for leaching the salts in salt affected soils. An operational problem with bed and furrow is that with the passage of time, the furrows become cemented due to silt deposition. Water then moves laterally and vertical seepage of the water reduces considerably. However with minor maintenance the problem can be overcome. 11 Since water is applied in furrows, the effect of water borne and water transmitted diseases on the crop health are minimal. The weeds, which are transported through canal water, are trapped in the furrows from which these can be removed or controlled easily. Moreover, the same field may be used for inter-cropping e.g. sugarcane in furrows and wheat on beds etc. The cost of the bed and furrow system is low and may consist of some tractor hours. Design: Azhar Saeed, IUCN Pakistan Country Office

12 IUCN-The World Conservation Union Founded in 1948, The World Conservation Union brings together States, government agencies and a diverse range of non-governmental organizations in a unique world partnership: over 1000 members in all, spread across some 140 countries. As a Union, IUCN seeks to influence, encourage and assist societies throughout the world to conserve the integrity and diversity of nature and to ensure that any use of natural resources is equitable and ecologically sustainable. The World Conservation Union builds on the strengths of its members, networks and partners to enhance their capacity and to support global alliances to safeguard natural resources at local, regional and global levels. IUCN Pakistan has six programme offices in cities from the north to the south, multiple field offices and a large portfolio of projects. It is one of the 7 Country Offices of IUCN's Asia Programme, covering 17 countries with a workforce of nearly 500. Where we are: IUCN Pakistan IUCN Pakistan Water Programme Country Office Balochistan Programme Office 1 Bath Island Road Marker Cottage, Zarghoon Road Karachi Opposite Railway Station Pakistan Quetta,Pakistan Tel: Tel: Fax: Fax: cro@iucnp.org bpo@qta.iucnp.org