Determination of irrigation scheduling thresholds based on HYDRUS-1D simulations of field capacity for multilayered agronomic soils in Alabama, USA

• DOI: 10.1016/j.agwat.2021.107234
• Publication Date: 2021-10-11T23:34:40Z
• Authors: Bruno Patias Lena; Luca Bondesan; Everton Alves Rod...; Brenda V. Ortiz; Guilherme Trimer ...; Hemendra Kumar
• Keywords: 2. Zero hunger; 0106 biological sciences; 15. Life on land; 01 natural sciences; 6. Clean water

Abstract The use of soil matric potential (ψ) sensors to support irrigation decisions has become common practice among many producers. However, ψ values at which irrigation should be initiated (ψlim) based on a pre-defined irrigation depth is still lacking. The main objectives of this study were: (i) evaluate the impact of different negligible drainage flux on estimated ψ at field capacity (ψfc) using HYDRUS 1D simulations; (ii) identify ψlim values and its corresponded irrigation depth under different soil profile depth at representative soil types in Northwest and Southeast Alabama. The ψ-θ relation at field capacity (ψfc and θfc, respectively) were estimated by a numerical internal drainage flux experiment for multilayered soils using HYDRUS-1D software simulations. Among the different negligible drainage fluxes (qfc) tested, a qfc value of 0.01 and 0.025 cm d−1 yielded the best results for the soil located at Northwest and Southeast Alabama, respectively. For a soil water depletion of 35% and a soil profile depth of 0.6 m, the ψlim ranged from − 103 to − 133 kPa for the soils located at Northwest Alabama and − 38 to − 51 kPa for soils located in Southeast Alabama. It returned an irrigation depth varying from 20 to 24 mm for Northwest Alabama soils and 15–33 mm for Southeast Alabama soils. For a same irrigation depth, it was observed that the ψlim increased (became less negative) as soil profile depth considered for irrigation calculations increased. Additionally, if the same pre-defined irrigation depth is used during the entire growing season, there is a high change that plants could be under stress due to the high level of water deficit. Using the same irrigation depth during the entire crop growth season could be a flawed irrigation management strategy; therefore, irrigation depth should dynamically change over the growth season as the plant roots reach deeper soil layers.