SPRINKLER IRRIGATION

DR. S.M ALAM
(feedback@pgeconomist.com)

Aug 23 - 29, 2010

Pakistan is largely an arid to semi-arid country. Agriculture heavily depends on the irrigation water supplies. Sprinkler irrigation is a method, which may play an important role on the efficiently utilisation of water, nutrients and chemicals for irrigation of the crops.

In the recent advancements, many scientific and technical research efforts have proven quite meaningful in developing suitable irrigation systems for different countries for growing vegetables or other suitable crops. Many methods and techniques have been designed, planned, developed and applied successfully in the agricultural fields/gardens etc. for the profitable marketing agriculture. Presently, versatile and powerful sprinkler irrigation techniques can be used economically under various soil topographic conditions, because it requires least land development. Initially, sprinkler irrigation method was used on high-value plantation crops such as coffee, tea, and orchards, but now it is gaining popularly on most of the food crops, orchards, and cotton.

This sprinkler system is particularly suited for sandy soils, where surface irrigation may be inefficient or expensive or where erosion may be particularly hazardous. In this system, quite low rates and amounts of water may be applied as the low amount of water is required for seed germination, delay of fruit budding, and cutting of crops in hot weather.

The important agricultural input such as fertilisers may be dissolved in the water and applied efficiently through the irrigation system. Sprinkler technique is classified according to principles of operation, pressure discharge, and material from which they are made. Sprinklers manufactured from bronze materials are considered to be resistant and longer lasting than those prepared completely or in part from aluminum. Different types include whirling, propeller, mini, and micro. Others may be (i) low angle jets - under canopy sprinklers, (ii) giant sprinklers - for irrigation of cereals and fodder crops, wide spacing covering large areas, (iii) part circle sprinklers, for part irrigation of marginal areas to prevent water wastage and wetting of roads.

While selecting a sprinkler, suitable reliable workable factors such crop, soil, quality of irrigation water, irrigation schedules, water availability or supply conditions such as pressure, discharge, labor, manpower, economic evaluation etc. must be taken into consideration. The sprinkler characteristics must also be considered such as quality of water application pressure and discharge range and sensitivity to wind etc. Medium-pressure sprinklers are the most widely used ones. If operated at a correct pressure and spacing appropriate to the nozzle, they give good uniformity of water application with little risk of damage to crop or soil except in sensitive cases. An irrigation system of sprinkler type is planned so that the correct amount of water will be applied efficiently at the right time. The system should be selected after a complete evaluation of planning considerations such as crop requirement for irrigation schedules, soil types, available water, infiltration rate, climate, precipitation, wind velocity and evaporation, water quality, water supply conditions, discharge, pressure and roper time, landscape topography and shape of the field, existing irrigation network and labor and economic factors. The basis of good and sound planning generally depends upon the provision of exact and reliable recorded data of the crop yields by the surrounding field farmer to the planner. This will include the topographical scale map with details of border, paths, direction of tillage and row and existing network, ditches, electricity lines, crop irrigation timing, water supply conditions, and water source, soil analysis, agro-technical considerations etc.

The main advantages of sprinkler irrigation are (i) expensive land leveling is not required, (ii) water saving-irrigation intensity can be changed in accordance with the infiltration capacity of soil, (iii) high efficiency due to uniform water distribution, (iv) no special skills-trained personal can operate the system reasonably well, (v) easy and uniform application of fertilisers and pesticides through irrigation system, (vi) possibility of applying a minute quantity of water for germination and other irrigation systems, (vi) frequent an light irrigation is possible, giving better response from the crops, (vii) increase in yield and quality, early ripening, water conservation and alternative value of specific periods, saving of labor, machinery, fertilisers and pesticides, (viii) soil moisture is maintained at optimum level by sprinkler irrigation.

Fertilisers and pesticides can be mixed, hence the efficiency of these inputs for crop production is more compared to surface irrigation. By introducing this system, there will be no soil erosion problem, no compaction of soil during irrigation. In recent years, sprinkler irrigation has become widespread irrigation method in cereal or tree crops as a result of numerous improvements both in the sprinklers and in the adaptation of the irrigation method to specific local conditions.

There are certain disadvantages in the use of sprinkler system, and these are: (i) higher initial cost, (ii) high and continuous energy requirement for operation, (iii) under high windy condition and high temperature, distribution and application efficiency is poor, (iv) highly saline water causes leaf burning, when temperature is higher than 95oF, (vi) when lands have been already leveled and developed for surface or other irrigation methods, sprinkler irrigation is not so economical, (v) loss of water due to evaporation from the area during irrigation, (vi) above canopy sprinkling may cause washing of spray, materials and aggravate the incidence of pests and diseases.

A stable and constant water supply is needed for the most introducing sprinklers irrigation technique for certain crops and certain locations. Such system can be made operative in the desert areas of the country. The areas of Balochistan, Thal, Thar, Cholistan and other sandy and barren areas of Pakistan are suitable for cultivation of vegetable crops. The sprinkler irrigation system is very much profitable in Middle East countries and other barren areas of the world. Sprinkler irrigation has immensely helped in developing UAE agriculture and forestry projects. The success rate could be judged from the fact that up to early eighties, the UAE used to import about 90 per cent of its total fruits and vegetable requirements from abroad, but only that figure has drastically reduced to less than 30 per cent. In some areas, they have surplus farm products, fruits, and vegetables for exports to the neighboring countries as well as to European countries and USA.

Sprinkler irrigation would enable farmers to produce maximum possible crop yield with minimum possible water supply from the reservoir. This method saves fertilisers, minimises labor costs, water usage, controls weed and maintains no soil compaction.