Evaluation and Improvement of Sugarcane Irrigation Water Management in Wonji Shoa Sugar Estate, Ethiopia

Abstract

Since the last two decades, irrigation development and expansion are rapidly increasing all over the country. With the increasing expansion and development of irrigation, the poor performance of the existing irrigation systems is becoming areas of concern. Improper management of irrigation has led to poor performances of schemes with many undesirable consequences like salinity, water-logging and overall sustainability problems of irrigation. In line with this the current study was undertaken on evaluation and improvement of irrigation water management practices at Wonji Shoa Sugar Estate. The general objective of the study was to evaluate irrigation water management practices for sugarcane under Wonji Shoa Sugarcane farm with the view to improve on-farm irrigation water management. Performance of current furrow irrigation practices was evaluated from ten selected fields with three commonly used furrow lengths (32, 48 and 64m). The performances of irrigation evaluated in term of application efficiency, distribution uniformity and deep percolation from field measurement were simulated using WinSRFR model. Sugarcane crop evapotranspiration and crop coefficient were determined and developed using lysimeter experiment at Melkassa Agricultural Research Center. The sugarcane NCO-334 was planted in the established lysimeter. Soil moisture was monitored using gravimetric method and calibrated neutron probe throughout the growing period of sugarcane. Reference evapotranspiration in the study area was determined using CropWat 8.0 model. Field experiment was conducted to analyze the effect of furrow irrigation design parameters on sugarcane growth, yield and quality parameters as well as on water productivity. The field experiment was laid out using split-split plot design with three factors as main factor (furrow slope, 0.05, 0.08 and 0.11), sub-factor (furrow length, 30, 50 and 70m) and sub-sub factors (furrow inflow rate, 4, 5 and 6l/s) replicated three times with three levels of each factor. All growth, yield and quality parameters were analyzed using SAS 9.4 software and mean separation was tested at 5% significance level for all parameters. For the three rates of water application, sugarcane water productivity parameters were determined from the field and simulated using AquaCrop model. The performances of current furrow irrigation current practices were in the rage of poor in terms all performance indicators used. Since the performance of current furrow irrigation was poor, an improvement options were developed by varying inflows rate (reducing) and cutoff time (increasing) decision variables. As a result, the overall performance of furrow irrigation was improved for all furrow lengths. More specifically, application efficiency and distribution uniformity were significantly improved. From these results it can be recommended that furrow irrigation decision variable should be redecided to achieve more efficient irrigation water management. The sugar cane evapotranspiration was measured throughout the growing period using lysimeter experiment. The result obtained indicated that crop evapotranspiration ranges from 1.63 to 7.13mm/day during the early and peak growth stages, respectively. The crop coefficients were found to be 0.42, 0.93, 1.26 and 1.05 at emergence, tillering, grand formation and ripening growth stages respectively. Hence, these results were obtained from a one season experiment, they can be useful as field measurement-based data are lacking in the area and other regions of Ethiopia. Additionally, performance different reference evapotranspiration models were evaluated as compared to Penman-Monteith method and Blaney-Criddle model was performed better under the current climatic. The effect of furrow slope showed statistically significance variation at 5% significance on growth parameters but non significant variation on yield components of sugarcane. But the effect of furrow length showed statistically significant variation on almost all growth and yield parameters of sugarcane at 5% significance level. Finally, the effect of furrow discharge rate on all growth and yield parameters considered has shown statistically significant variation at 5% significance level. In general, from the three furrow discharge rates, 4l/s resulted in a better sugarcane growth and yield parameters. The effect of furrow slope, furrow length and furrow inflow rate on all sugarcane quality parameters showed statistically non significant variation. The sugarcane water productivity as simulated using AquaCrop model showed higher values than for the three-irrigation application rate. Generally, it can be recommended that, while improving the current irrigation water management practices requires selection of the right combination of operational decision variables, the furrow irrigation design parameters and decision variables should be reconsidered for the new setup of furrow system. Although under data scarcity condition, the sugarcane crop water requirement and coefficient determined in this study can be useful, it must be noted that the information generated are based on a one-time experiment.