Abstract
This study was aimed to compare estimation methods of crop water requirement and irrigation scheduling for major crops using different models and compare the significance of models for adoption in different situations of the Metekel zone. Crop water requirement and irrigation scheduling of maize in selected districts of Metekel zone were estimated using CropWat model based on soil, crop and meteorological data, and AquaCrop based on soil, crop and meteorological data including Co<sub>2</sub>, groundwater, field management, and fertility status. Model performance was evaluated using Normalized Root mean square errors (NRMSE), model by Nash-Sutcliffe efficiency (NSE), Prediction error (Pe), and Model efficiency (MF). It is observed that the maximum reference evapotranspiration in the study area was found to be 7.1 mm/day in Guba and the minimum reference evapotranspiration was 2.9 mm/day in Bullen district. In all cases, the maximum ETo in all districts was fund to in March and the lowest in August. The maximum ETc of maize was found to be 702.4mm in Guba district and the minimum ETc was found to be 572.6mm in Bullen district using CropWat but the effective rainfall (Pe) for maize was determined as 185mm respectively in Wembera district. However, using the AquaCrop model the maximum ETc of 565 mm was recorded in Guba but 425 mm was recorded as a minimum in the Wembera district for irrigated maize in the study area. The study revealed that the irrigation scheduling with a fixed interval criterion for maize 10 days with 12 irrigation events has been determined. Moreover, furrow irrigation with 60% irrigation application efficiency was adjusted during irrigation water applications for all districts. The performance of the irrigation schedule and crop response was evaluated by the analysis results in the simulation using different models. It has been observed that there were a strong relationship and a significant relation between the simulated and observed values for validation. Hence, Normalized Root mean square errors (NRMSE), model by Nash-Sutcliffe efficiency (NSE), Prediction error (Pe), and Model efficiency (MF) showed that the AquaCrop model well simulated in all parameters considered. AquaCrop model is the most suitable soil-water-crop-environment management model, so future studies should suggest a focus on addressing deficit irrigation strategy with different field management conditions to improve agricultural water productivity under irrigated agriculture for the study area for major crops.
Highlights
Irrigation implies the application of suitable water to crops in the right amount at the right time [11] Irrigation scheduling is important for developing best management practices for irrigated areas [5]
Long -term climatic data of the study area was analyzed and reference evapotranspiration (ETo) was calculated based on the FAO Penman-Monteith method [6] and the results are given in the following figure 1
It is observed that the maximum reference evapotranspiration in the study area was found to be 7.1 mm/day in Guba and minimum reference evapotranspiration was 2.9 mm/day in Bullen district
Summary
Irrigation implies the application of suitable water to crops in the right amount at the right time [11] Irrigation scheduling is important for developing best management practices for irrigated areas [5]. In Metekel zone, almost all farmers are poor in water resource management and lack of experience and knowledge about how much and when to irrigate efficiently for irrigation water saving-strategies to tackle the shortage of rainfall and dry spell [10]. This results in waterlogging, soil erosion, accumulation of salt, and loss of irrigation water resources. The comparative study using the CropWat and AquaCrop model for the determination of crop water requirement and irrigation scheduling of major crops in the study area hasn’t been done yet to the best of my knowledge
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