Validation of Aquacrop for Different Irrigation Regimes of Onion (<i>Allium Cepa</i>) in Bontanga Irrigation Scheme

Abstract

Crop water productivity models are important tools in evaluating the effect of different irrigation regime on crop yield. AquaCrop model is a crop water productivity model adopted by the Land and Water Division of FAO in the year 2009. It simulates yield response to water for herbaceous crops, and it is particularly suitable in addressing conditions where water is a key limiting factor in crop production such as in northern Ghana. The objective of this study was to calibrate the AquaCrop model for different irrigation regimes for onion (Allium cepa), to determine its effect on crop growth and yield parameters of the crop at the Bontanga irrigation scheme. To achieve these, the Randomised Complete Block Design (RCBD) was used on Red Creole onion variety. RCBD was made up of four irrigation treatment regimes, 117%, 100%, 80% and 60% crop water requirements (CWR) of onion, with five replicates. Results indicated that there was no significant variation in yield, dry bulb biomass and total biomass, but there was difference for dry leaf biomass of onion at 0.05 significance level. The AquaCrop model simulated satisfactorily the crop yield, biomass and evapotranspiration water productivity of onion. There was a strong correlation and a significant linear relation between the simulated and measured crop yield, biomass and evapotranspiration water productivity. Validation of AquaCrop model using Nash-Sutcliffe efficiency (E), Root mean square errors (RMSE) and index of agreement (d) showed that, AquaCrop model can be used to simulate CWR of bulb crops, such as onion.

Evaluation of Aqua-Crop Model using Onion Crop under Deficit Irrigation and Mulch in Semi-arid Nigeria

“…The result revealed that irrespective of the level of irrigation and mulch, the observed values for both Onion bulb yield and biomass recorded were underestimated by the Aqua-Crop model except at 100% irrigation with white synthetic mulch with a % deviation of 0.7. The result was in line with a report by Agbemabiese et al (2017) which suggested that crop yields were overestimated at 10% irrigation level and underestimated at deficit levels. The highest model values of 6.09 ton ha-and 8.24 ton ha-1 of bulb yield and biomass respectively were recorded at 100% irrigation under white synthetic mulch.…”

“…This could be as a result of a larger % deviation of ETa that was observed at water-stressed plots. This result was in line with the findings byAgbemabiese et al (2017) which states that the Aqua-Crop model underestimated ETwp. The % deviation observed between the observed and simulated ETwp values were fairly estimated for most of the treatments as shown in Table4.…”