Abstract
Aim: This study focused on the seasonal dynamics of energy fluxes over selected agro ecosystems (alfalfa and corn crops) to understand the role of energy partitioning in determining the mechanisms controlling the crop water requirement and irrigation schedules.
Methodology: Eddy Covariance (EC) flux tower was installed on a center pivot irrigated field located in the Eastern Region of Saudi Arabia. EC data of nearly three years (May 2013 to March 2016) was analysed for variations in agro-climatic conditions, energy fluxes and their partition under both cropped (alfalfa and corn) and non-cropped (fallow) scenarios.
Results: Three-year mean net radiation (R,) varied from 106.8 to 816.54 Wm(-2), while the recorded sensible heat, soil heat (G) and latent heat fluxes were 291.6, 158 and 3.8 Wm(-2), respectively. The latent heat was more during the crop growing season (381.38 W m(-2)) compared to fallow (23.89 W m(-2)); while, sensible heat showed an opposite trend compared to latent heat. The sensible heat recorded during the growing season (38.42 W m) was much lower than for the fallow season (28135W m(-2)).
Interpretation: There was contrasting variations in sensible heat and latent heat fluxes across seasons and corresponding to the changing climate and surface conditions of the field. In the case of silage corn, the proportions of partitioned energy to sensible heat (12.4%) and latent heat (18%) were higher than alfalfa. However, during the alfalfa post-harvest practices, the latent heat flux was always less as the available energy was partitioned as sensible heat rather than latent heat flux.