The aim of this article is to point out the chances for a method-specific reduction of the water- and energy input in irrigation of agricultural and horticultural crops. A brief analysis of the common irrigation methods is given and proposals are made for further technical development towards an increase in water- and energy efficiency of mobile and semi-mobile irrigation machines. the proposed concept of mobile drip irrigation is applicable to both, the boom trailer irrigation and the centre pivot or linear move machines. The main characteristics values for the selection of a proper system are given together with the empirical appraisal of their applicability.
While the efficient scheduling of irrigation is one of the best ways to save water, the efficient use of irrigation equipment must not be overlooked. To ensure functional efficiency and the ultimate success of irrigation systems, the equipment that is used in these systems must comply with certain performance standards.
A program for evaluating irrigation equipment, which included the development of appropriate test facilities, was therefore established within the ARC-Institute for Agricultural Engineering (ILI) who is an independent evaluation authority on the performance of irrigation equipment and systems.
Highly technological test benches for a large variety of irrigation equipment were developed and installed in two Hydrolabs at the Institute, which guarantee accurate measurements on the quality and performance of these products. A number of unique test programs and test instruments were also developed.
For the purpose of water conservation in the framework of the development of micro-irrigated citrus area in Tunisia, the operation of irrigation systems and susceptibility to clogging using conventional and marginal water could be minimised.
The present paper describes the principal results of an inquiry focussed on citrus fruits farms located in the region of the Cap Bon (Tunisia). This inquiry aims at analysing some technical aspects on a reduced area: the Beni Khalled region.
The main purposes of this study are to identify the additional means required for preventing micro-irrigation systems from clogging, when subjected to different qualities of water and to develop a methodology for controlling emitters working conditions.
The inquiry identifies the technical level of equipment, the scheduling and maintenance practices on a sample of 100 citrus fruit farms in Cap Bon. In addition, for 20 farms located in the Beni Khalled area, flow rate uniformity of representative micro-irrigation systems has been assessed in field conditions.
In order to better characterize the performance of a given microsprinkler, tests were conducted at the University Campus, Pantnagar, India during 1997-98.Eight commercially available spinner type microsprinklers, designated for reference as Make A,B,C,D,E,F,G and H of different nozzle sizes of 1.50, 1.60, 1.73, 1.92, 2.00, 2.10, 2.34 and 2.80 mm, respectively were selected for testing purpose. Tests were conducted for four different operating pressures ( 0.5, 1.0, 1.5 and 2.0 kg/cm2 ) and four riser heights (20, 35, 50 and 65 cm). Studies revealed that radius of throw increases with increase in both the operating pressure and riser height of the microsprinkler. The rate of discharge increases both with increase in nozzle size and operating pressure and decreases with increase in riser height. The effect of riser height and operating pressure of microsprinkler was minimum on mean depth of water for all the microsprinklers tested. Based on CV criteria, the microsprinklers of Make A, C, F and H considered having good performance characteristics (CV < 100 % ) at all the pressure and riser heights. For non- overlapping patterns, Make E microsprinkler had better performance characteristics in terms of Cu followed by Make A, H and F microsprinklers. Uniformity of water distribution increases with increase in operating pressure and decreases with increase in microsprinkler spacing for different overlapping and the performance of Make H microsprinkler was found to be better than other makes of microsprinklers.
Many tobacco growers in Zimbabwe have limited water and financial resources. Drip irrigation applies water with greater efficiency than the conventional hand-move sprinkler system, but capital costs are higher. The portable drip system reduces capital costs and makes use of farm labour which is not currently a production constraint. The amount of irrigated tobacco grown using this system has increased from 793 ha in 1996 to 1226 ha in 1998 and is set to further increase in the future. This paper describes the operation, advantages and disadvantages of the portable drip system.
1 MBB Consulting Engineers Inc, P O Box 3011, Stellenbosch, 7602 South Africa
2 Department of Agriculture and Food Engineering, University of Pretoria, Pretoria, 0002 South Africa
The paper addresses the results obtained from a WRC funded project with the above-mentioned title undertaken over the past four years. The project was completed by MBB Consulting Engineers and comprised of an in-depth investigation into the practical application possibilities of micro and drip-irrigation by small-scale farmers. This was done by installing and monitoring a number of systems, on-farm, under the management and control of small-scale farmers, as well as field visits to a number of existing systems operated by individual farmers, and a number of existing micro-irrigation schemes.
A total of 11 micro and drip-irrigation systems were installed on small-scale farming sites in the Northern Province, the Western and Northern Cape, and monitored to a greater or lesser extent over a period of two and a half years. A number of the trials failed for various reasons, and it was decided to include the monitoring of other existing systems, which added some very important information to the study. During the project field work, the researchers learnt valuable lessons which could be applied in future projects of this nature.
As a result of the research, guidelines on the management requirements of micro-irrigation systems and other factors affecting system choice and appropriateness for small-scale farmers were developed. The guidelines are aimed at small-scale irrigation farmers, irrigation advisors, planners, designers and development funders, and will be discussed in the paper.