Design And Hydraulic Performance Of Linearly Moved Irrigation System

Irrigation potential is regarded as one of the prerequisites for agricultural development in a country due to the uncertainty of rainfall, uneven distribution of rainfall, crop water requirements, nature of the soil, utilization of river water effectively and to maximize production.The Linearly Moved Irrigation System (LMIS) was developed in response to the problems of covering the corners and runoff associated with centre-pivot irrigated fields and also to be used by poor farmers and to suit the prevailing conditions and requirements of the respective areas.Water application uniformity potentially affects crop yield and water use efficiency. Modeling the effect of irrigation non- uniformity on yield has been widespread and productive works showed that increasing irrigation nonuniformity decreases yield. AquaCrop provides the means to simulate this behavior. Although AquaCrop is based on complex crop physiological processes,it uses a relatively small number of explicit and mostly intuitive parameters with simplicity and accuracy, and the possibility of optimizing yield by using the appropriate irrigation strategy.Hence it requires a local calibration to simulate realistically based on the new irrigation system.It is in this regard that this research was conducted to: (1) design and parameterize a more suitable, effective and less expensive system; (2) assess the real distribution uniformity of irrigated water using LMIS with respect to the effects of different parameters (height, space,pressure), and formulate and propose a new equation to calculate the uniformity of sprayed irrigation; (3) compare and develop a model of fixed spray plate sprinkler (FSPS) droplet dynamics introducing empirical equations for droplet characterization with respect to operating height and pressure; (4) monitor the varying uniformities of water applied by the LMIS and to evaluate the importance of sprinkler uniformity to the tomato yield; (5) calibrate and test AquaCrop for tomato grown under full and deficit irrigation in the tropics and compare yield results with the newly designed LMIS evaluation results.In the first study, a new LMIS was designed and built. The purpose of this new invention is the ability to provide a small light precision irrigation sprinkler removable rack to be able to adapt to the complex terrain structure with its simplicity, easy to operate, easy to move, high efficiency in spraying water, spray uniformity and low energy consumption. The device includes frame angle,reinforcement, a support rod, the top slot truss, wheel and so on. It must be re- echoed that the aim should be to adapt or redesign technology flexibly so as to suit the prevailing conditions and requirements of the respective areas. An estimated annual cost of US$324.07 will be required to irrigate a hectare of land per year using the LMIS which proves to be relatively cheaper and affordable to small holder farmers within the sub-Sahara African region.The second study related to the optimization of the LMIS, where its distribution uniformity performance was assessed under varying conditions. Water distribution coefficients used in the performance assessment were Christiansen's coefficient of uniformity (CU %), distribution uniformity (DU %), scheduling coefficients (Sc) and the coefficient of variation (CV %). Values for CU ranged from 82.30% to 93.17% and that of DU ranged from 70.39% to 88.44% at varying operating pressures and different height scenarios. Also Sc values ranged from 1.13 to 1.42 with CV values ranging from 10.3% to 22.5%. On further analysis,using the stratified sampling method of determining the uniformity (CUSR) postulated in this research, it was observed that values for 10psi, 15psi and 20psi for the two different height positions (100cm and 150cm) ranged from 0.99 to 1 which reaffirms the fact that the uniformity displayed by the system was generally appreciable. The best operating condition recorded was at 20psi and 150cm which correspond to practical situations of high pressures and high sprinkler nozzle heights.In the third study, the experiments on the hydraulic performance of the spray heads were carried out, and empirical equations of individual water distribution pattern and discharge-pressure relation were developed. Models were built for the water distribution and droplet diameter of the D3000 spray heads with coefficient of determination for the empirical equations ranging from 95.0% to 99.6% with respect to the operating pressures and two different height positions. The results showed that various arrangements of the sprinkler could greatly change droplet and water distribution characteristics. The study concluded that the irrigation uniformity of a sprinkler irrigation system is more affected by the combination of distance from sprinkler, riser height and operating pressure.In the fourth study, field evaluation of tomato growth and yield affected by the uniformity of sprinkler-applied water was measured. The field experiments conducted in this study demonstrated that the uniformity of sprinkled water had an impact on the fruit yield of tomato.From the results obtained, both coefficient of uniformity and distribution uniformity of the sprinkler irrigation system were increased with increasing both the operating pressure and the riser height. This became evident as it reflected in plant height, stem girth, number of leaves,number of fruit per plant, fruit yield and crop water productivity of tomato.The fifth study involved the calibration and validation of AquaCrop for deficit and full irrigation of tomato. Comparing the yield of the tomato (100% ETc restoration) under the LMIS to that of the validated results of both simulated (AquaCrop) and measured values of yield of tomato it was generally observed that the mean values obtained under the LMIS for all set of combinations were higher than for both simulated and measured yield values of tomato. This depicts that LMIS could be a useful irrigation system for tomato cultivation. However, it must be emphasized that the simulated data suffered from lack of data on the crop canopy cover which is a very important parameter used in developing the model. Also the incidence on pest and diseases could have contributed to the lower yield values recorded for the measured values under the rain shelter.Among other things, the main novelties in this dissertation are as listed in the following: Design and parameterization of the Linearly Moved Irrigation System. Formulation and proposal of a new equation used to calculate the uniformity of sprayed irrigation water. Empirical equations for the water distribution from FSPS were also developed. Furthermore, calibrating and validating AquaCrop for tomato grown under full and deficit irrigation and comparing yield results with those obtained by the newly designed LMIS are publicized in this research work.