Developing And Testing Simple Weighable Lysimeter For Measurement Of Crop Water Requirement And Evaluation Of Crop Evapotranspiration Estimation Models

Abstract

Scarcity Of Water Is A Growing Challenge In Agriculture, Making Efficient Irrigation Planning And Management Essential. Accurately Determining Crop Water Requirements Is Critical For Optimizing Irrigation, With Direct Lysimeter Measurements Providing The Most Precise Results. However, Lysimeter-Based Experiments Are Often Limited Due To High Costs, Lack Of Laboratory Facilities, And Equipment Constraints. As An Alternative, The Kc-Approach, Which Estimates Crop Water Needs By Multiplying Reference Evapotranspiration (Eto) With Crop Coefficient (Kc), Is Commonly Used In Data-Scarce Regions. In Line With This, The Current Study Was Aimed At Developing And Testing Simple Weighable Lysimeter For Measurement Of Crop Water Requirement And Evaluation Of Crop Evapotranspiration Estimation Models. The Developed Lysimeter Was Tested For Its Performance In 2023 And 2024, Successfully Detecting Soil Moisture Variations As Small As 0.2 Mm, Ensuring Precise Water Requirement And Crop Coefficient Measurements. Field Experiments At The Melkasa Agricultural Research Centre Were Conducted To Determine Water Requirements And Crop Coefficients Of Onion (Allium Cepa L.) And The Result Revealed A Seasonal Crop Evapotranspiration Of 460.27 Mm, With Crop Coefficient Values Of 0.68, 0.89, 1.03, And 0.86 For The Initial, Developmental, Mid-, And Late-Season Stages, Respectively. Additionally, Ten Eto Models Were Assessed For Their Accuracy, And The Hargreaves And Blaney-Criddle Equations Were Calibrated In The Kc-Approach, Using Lysimeter-Measured Onion (Allium Cepa L.) Evapotranspiration. The Calibration Significantly Enhanced The Accuracy Of Both The Hargreaves And Blaney-Criddle Equations, With The Hargreaves Coefficient Increasing By 48% (From 0.0023 To 0.0034) And The Blaney-Criddle Coefficient Decreasing By 9% (From 1 To 0.9135). The Results Indicated That The Calibrated Hargreaves And Blaney-Criddle Models Were The Most Accurate Alternatives For Estimating Eto In The Study Area And Regions With Similar Climatic Conditions. Overall, This Study Provides Valuable Tools For Optimizing Irrigation Management In Data-Scarce Regions, Contributing To Improved Water Resource Utilization And Irrigation Scheduling In Semiarid Climates.