COMPARATIVE STUDY ON PERMANENT AND SEMI-PERMANENT SPRINKLER IRRIGATION SYSTEM DESIGN FOR ONION CROP IN THE HILLY LANDS OF NYAGATARE DISTRICT, RWANDA

Abstract

The Population of Rwanda is increasing at an alarming rate, and steps have to be taken to meet its food and fibre requirements and to ensure food security, as well as to maintain the national economy which is mostly depending on Agriculture. According to the Ministry of Finance and Economic Planning 2012, Agriculture contributes more than 40% to the national GDP. However, this economy largely depends on rain-fed agriculture and the rainfall may be adequate but unevenly distributed throughout the growing season or unreliable distribution from year to year. Realizing this fact, a Sprinkler Irrigation System was designed in Matimba sector near Muvumba River in Nyagatare District (Eastern province) to cope with dry season and improve land productivity. The main objective of this study was to design a Sprinkler Irrigation System in proposed area for hill side irrigation. To achieve the final results, three points are explained in methodology chapter: the collection of field data, the preliminary design, and the final design or design adjustment, where more formulas from sprinkler irrigation papers, tables and charts were used. Two types of sprinkler irrigation system are designed to irrigate Onion (the crop was chosen due to its high economic value in the country): the Permanent System Design and the Semi-Permanent System Design, on the rectangular pattern with spacing of 12x24m, for the sample study area of 6ha. Based on this study, the preferable design that would suite most has been recommended basing on economic and technical aspects: time for irrigation completion, labour and cost of irrigation, power required, security and operation and maintenance, but most importantly Annual Net Benefit. The final results of the study revealed that the Semi-Permanent Sprinkler Irrigation System is a better method for irrigating dry-onion crop of maximum rooting depth of 60cm within the crop period of 120 days. The crop water demand is calculated by use of the CROPWAT computer program version 8. The proposed power source for driving the pump is electricity, with 53 HP per irrigation cycle of 10 days. Only 4 laterals are operating at the same time in split-line. The set time is 7.6 hrs and the total field is covered in 5 days, leaving the other 5 days free for break.