TRICKLE IRRIGATION SYSTEM
DR.S.M.ALAM, DR.A.H.SHAIKH & DR.T.HUSAIN
July 21 - 27, 2008
Water is becoming limited and expensive commodity in many crop productive areas of the country, particularly when applied by inefficient overhead sprinkler irrigation method. Frequently, water shortages occur at times of critical and economic crop growth. Therefore, growers or farmers need to be efficient in their use of irrigation. Sprinkler efficiencies, such as losses to wind, high pressure pumping, and evaporation call for improved methods of irrigation compared with the traditional overhead watering. Irrigation efficiencies are the amount of water applied to the root zone divided by the amount taken from the water source. Trickle irrigation is a method of irrigation through pipes to the crops.
We may define trickle irrigation as the precise slow application of water in the form of discrete drops, tiny streams, or miniature sprays of mist through mechanical devices called ejectors/emitters or applicators located at different selected points along water delivery lines in the system designed. At present, trickle irrigation has become wide spread irrigation methods in crop plants, as a result of numerous improvements in the adaptation of the irrigation method to specific local conditions. Although, trickle-irrigation is used primarily for the application of water to crops, it is a multipurpose system with a wide range of uses. This method was ascribed to the uniform wetting of the irrigation area and to the correct amounts of water range required by the plants; which is applied uniformly to given volume of soil. This enables the plant root system to develop evenly and to spread densely throughout the wetted soil volume, thus ensuring the smooth supply of water and nutrients to the crops.
This situation is somewhat different on tree crops that are mainly rain fed and need only supplementary irrigation for relatively short, but critical periods. Here, the root system develops according to the natural rainfall and the trickle irrigation can supply the required quantity of water and nutrients accurately and efficiently to the already developed root systems. The uniform irrigation rate of Trickle irrigation makes easy to calculate the amount of water be applied to the crop. By applying the right amount of water at the correct irrigation water rates, there will neither be seepage beyond the root zone, nor problems of aeration in the root zone caused by water logging. It is well known that the distribution of roots pattern itself on the water distribution in soil.
The trickle irrigation system meant for growing of vegetables and many other crops involve significantly the usage of water agriculture, farm products and a fore station project. It has been established that maximum possible production of crops are generally achieved as the water is supplied drop by drop to the plant's roots, using coil type drops, connected to a well or water reservoir through powerful pumps and pumping system, driven by either diesel engines or electric motors. It has been found that the high yields and fruit weights by trickle irrigation system are complimented with water savings of up to 50% and even greater, thus having a large, reduction in expenses. Trickle irrigation wet about 80 per cent of the soil surface in a mature orchard.
The area wetted by the trickle can be adjusted according to the development of the root system. In all the irrigation systems, one of the main aims is to prevent the accumulation of salts in the root zone. This is especially important, when the irrigation water is brackish or saline. Stalinization of the soil generally damages the root systems. It has been shown that salinity level in the root is lower under trickle irrigation than under other conditions. Trickle -irrigation permits the introduction of fertilizers into the soil with the irrigation water which has the advantage of lower labor requirement and higher fertilizer efficiency. Trickle irrigation is economical to install, because of the low discharge rates. Growers may also apply insecticides and fungicides less often because the applied spray will not be washed off as-with sprinklers. Also, the growers/farmers can avoid fungal diseases by reducing excess leaf moisture of the soil water-holding capacity, which directly affects its ability to provide the plant with adequate water. Recent experiment, carried out by US scientists, found that the yields data obtained for tomato, pepper and soybean were higher for the trickle irrigated compared with the spunkier irrigated plots.
The trickle irrigation system is also feasible in Pakistan. But, the initial capital cost of the standard trickle irrigation equipment is considered to be its limitation for large-scale adaptation in Pakistan. Therefore, the high cost and economic consideration limits its application to fruit trees and vegetables of high value crops in specific areas only. However this system can be beneficial in areas like, Thai, Cholistan Deserts of Punjab, Thar in Sindh, Coastal belts and open plains of Balochistan, where the water is scare and only high value crops are grown. The use of trickle irrigation, which utilizes pipe to convey the water directly to the plants, makes the development of the most sandy lands and rough topography practical even with relatively saline water. Thus, a totally new class of lands becomes available for irrigation and development by application of trickle irrigation technology. The cost of the system depends mainly on the spacing of laterals. For fruit trees, the trickle system is even more economical than sprinkler irrigation, whereas, for closely spaced, vegetable sprinkler system is more feasible.
The main item of expenditure in the trickle system is the lateral lines, however, the wider the row spacing the lesser the initial cost. In general, the laterals alone cover over 60%-of the total cost. Crops like grapes, apples, almond, papayas, guava, citrus, coconut and other fruit trees can be successfully grown on trickle irrigation system. During the past three decades realizing the potential of trickle irrigation system some private companies have catered in the marketing and supply of important trickle system. Little water is lost to deep percolation, consumption by weed or soil surface evaporation. Research results and reports in the US indicate that trickle irrigation increases cotton yield by more than 8%, while using 24% less applied water as compared to surface irrigation. The effective water control is possible if trickle irrigation can be applied efficiently. The low rate of water experiments on crops like tomato, grapes and sugar beet have resulted in significantly earlier maturity as attained with other irrigation systems. With trickle irrigation, water as salty as 4 desiisiemens (dS) per m can be used for crops. Trickle irrigation's primarily valuable to row crops, orchards and vineyards. Practically, trickle irrigation can not be adopted for cereal and other close growing crops.