Strategy For Improving The Perofrmance Of Sprinkler Irrigation

P.P.Shelke INTRODUCTION: Study of field sprinkler irrigation systems in Sikar district of Rajasthan  was undertaken.  Study was aimed at the performance evaluation of the sprinkler systems and analysis of net income of farmers by use of sprinkler irrigation.  Droplet size distribution of commonly available sizes of sprinkler irrigation systems was also studied.  The experiment for study of droplet size distribution were carried out at the College of Technology, Govind Ballabh Pant University of Agriculture and Technology, Pantnagar.  A computer model was developed to simulate the overlapping pattern between four sprinklers.  The model needs input in the form of quarter distribution from single sprinkler. OBSERVATIONS FROM SURVEY:  It was observed that the sprinkler irrigation was popular among the small land holding farmers, because of higher amount as subsidy, convenience of operation of system and its utility in saving water and unleveled land.  Mainly  Mahaveer and Jindal makes of sprinkler were popular among the farmers.  Farmers were using 7.5 hp and 10 hp pumps.  It was observed that due to higher suction and delivery heads most of the available head was consumed in lifting the water.  Therefore, the farmers were operating their systems at low pressure.  About 60 percent farmers were using the operating pressure less than 1 Kg/cm2.  Others were using their systems at an operating pressure up to 2.11 Kg/cm2 . It was observed that due to friction with water containing some amount of sand particles, there was a wear in nozzle orifice.  This resulted in variation of radius of coverage from the rated one, some variation was also done due to incompatible nozzle sizes used by the farmers.  Jet break up index of sprinklers was compared with the calculated jet break up index., from the manufacturers performance charts.  It was found to increase with pressure.  There existed a difference between observed and expected jet break up index because of nozzle wear and improper nozzle size by the farmers. It was observed that the farmers were using the lateral spacing's which were not within the recommended range.  About 35 percent of the total studied farmers were using the lateral spacing less than 55 per cent of wetted diameter of sprinklers, and 65 per cent farmers were using the spacing between 60 percent to 90 percent of the wetted diameter of their sprinklers.  Due to wider spacing, the uniformity of water application was affected, resulting in improper crop growth. UNIFORMITY COEFFICIENT AND DROPLET SIZE DISTRIBUTION: Uniformity coefficient was determined for some of the sprinkler systems.  It was observed that uniformity coefficient was higher , when the operating pressure was around 2.11 Kg/cm2. The study of droplet distribution of some commonly available makes ( Premier, Voltas and EPC Rolland) of sprinklers conducted at low pressure of 1 Kg/cm2 .  It was found that finer droplets were emitted at nearer zone of sprinkler coverage, and slightly bigger droplets were emitted at a farther distance of sprinklers.  It was observed that the Voltas make of nozzle emitted quite large size of droplets in the nearer zone of coverage from sprinkler, as compared to other makes.  This was because the nozzle was older than the other makes and was used several times for experimental purposes. MANAGEMENT PROBLEMS: A study of problems encountered by farmers in using sprinkler systems suggested that if the farmers could be trained appropriately to take care of their systems, the minor repairs could be done by farmers themselves. Opinion survey of farmers was done regarding the utility of sprinklers.  It was observed that the popularity of the sprinkler system was mainly because of the i) no necessity of attention during irrigation ii) labour saving iii) its versatility in unleveled land and iv) water saving. It was observed that the area under a crop was not significantly related to its yield levels.  However, it was observed that the yield of most of the crops was significantly related to irrigation application.  For wheat, barly and bajra the relationship was linear, however the yield of groundnut was related to water application by a power form of equation. A study of benefit cost ratio for one agricultural year indicated that the ratio of benefit to cost lied between 1.75 to 2.14.  The average income per hectare of farmers was between Rs. 2788.40 to 3276.90. SIMULATION MODEL: A computer model in FORTRAN 77 was developed which gives an overlapping pattern of four rectangular spaced sprinklers.  The input of the model is a quarter distribution from single sprinkler.  The model was tested on a  hypothetical quarter distribution , but there needs to be further experimental verification to establish the difference between observed and predicted uniformity coefficient. STRATEGY:    Based on the "Study of Field sprinkler Irrigation in Sikar District of Rajasthan" following strategy can be used for improving the performance of sprinkler irrigation. 1. Unlike the present practice of improper overlapping of sprinklers it is desirable that lateral spacing should be kept such as to provide 50 per cent overlap of the wetted diameter and thus a good uniformity of coverage. 2. Genuine spare parts, presently not available conveniently to the farmers, should be made available and recommended for replacement of worn out parts of already installed sprinkler systems as and where necessary. 3. It is desirable that the sprinkler system should be operated at a pressure closure to the manufacturers specifications, such as to get good uniformity of coverage, and droplet distribution. 4. To encourage the use of sprinkler systems, their repair and after sale services should be strengthened by the state agencies and dealers, to make it easily and economically available at the village level. 5. A short term training for farmers, regarding installation, operation and maintenance of sprinkler system should be arranged by all concerned agencies.

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