Sprinkler irrigation
The technique can be used economically under various soil topographic conditions because it requires less land development. Initially, the method was used on coffee, tea, and cardamom crops, which now has gained popularly in most food crops and cotton.
Sprinkling is normally suitable for sandy soils where surface irrigation may be inefficient or expensive, or erosion, hazardous. The system utilizes low amount of water in seed germination.
Fertilizers may be dissolved in the water and applied efficiently through this type of irrigation. The sprinkler technique is classified according to the principles of operation, pressure discharge, and material from which they are made.
Sprinklers manufactured from bronze materials are considered to be resistant and long lasting than those prepared completely or in part from aluminium. 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, (iv) pop-up sprinkler for lawns and house gardens, and (v) regulated sprinklers.
With micro-sprinklers, the water-jet fitted in the system strikes a bearing with one or two channels causing the sprinklers to rotate quickly for water distribution. When selecting a sprinkler, suitable reliable workable factors such crop, soil, quality of water, irrigation schedules, water availability or supply conditions such as pressure, discharge, labour, manpower, economic evaluation etc., are taken into consideration.
The sprinkler characteristics are also considered, such as quality of water application pressure and discharge range and sensitivity to wind etc. Medium-pressure sprinklers are the most widely used.
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.
The sprinkler irrigation is selected after complete evaluation of planning considerations such as irrigation schedule, soil types, available water, infiltration rate, climate, precipitation, wind velocity and evaporation, water quality, supply conditions, discharge, pressure and roper time, landscape topography and shape of the field, existing irrigation network, and labour and economic factors.
The basis of good and sound planning generally depends upon the provision of exact and reliable data of crop yields by the surrounding field. This includes 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. Wise and honest planning provides efficient and long-term solutions by striking a balance between the crop requirements and the desires of growers.
The advantages of sprinkler irrigation, are: (i) no expensive land levelling is required, (ii) water saving-irrigation intensity can be changed in accordance with the infiltration capacity of soil, (iii) uniform water distribution provides high efficiency, (iv) easy operations, (v) uniform application of fertilizers and pesticides, (vi) application of minute water quantity for germination and other systems, (vi) frequent and light irrigation with better crop response, (vii) increased yield and quality, early ripening, water conservation and alternative value of specific periods, saving of labour, machinery, fertilizers and pesticides, (viii) maintenance of soil moisture at optimum level and attainment of 20 yields in some crops with quality product.
Fertilizers and pesticides can be mixed efficiently as compared to surface irrigation. Fertilizer can also be applied through sprinkler system which saves labour. This system guarantees no soil erosion and compaction during irrigation. In recent years, sprinkler irrigation has become widespread in cereal or tree crops. Although, sprinkler system is used primarily for the application of water to crops but it is multipurpose with a wide range of uses.
The disadvantages are: (i) steep initial cost, (ii) excessive and continuous energy requirements, (iii) high winds and temperature reduces distribution and application efficiency, (iv) saline water causes leaf burning when temperature is higher than 95oF, (vi) on levelled and developed surface, sprinkler irrigation is not economical, (vi) loss of water due to evaporation, (vii) above canopy sprinkling may cause washing of spray, materials and aggravate the incidence of pests and diseases.
Such system can operate in deserts. Balochistan, Thal, Thar, Cholistan and other sandy and barren areas are suitable for the cultivation of vegetable crops.
The sprinkler irrigation system is profitable in the Middle East countries. The system has immensely helped in developing the UAE’s agriculture and forestry projects. The success rate could be judged from the fact that up to early 80s, the UAE used to import about 90-95 per cent of its total fruits and vegetable requirements. The figure is drastically reduced to less than 30 per cent.
In some areas, they have surplus farm products, fruits and vegetables for exports to neighbouring, and as well to European countries and the US. This situation has helped in improving weather conditions and environments as top summer temperatures are reduced in 25 years by about 5-7 degrees centigrade. As water supply in the world is dropping down with each passing day, it is eulogized that the sprinkler irrigation system is a key to the development of agriculture and forestry projects all over the world.