Dry mass production and water use of non- and drip irrigated Thuja occidentalis Brabant: field experiments and modeling

Generally, irrigation increases dry mass production (DM) on sandy soils of horticultural crops and at the same time increases the risk of percolation losses of water and chemicals to below the root zone. However, the effects of irrigation are highly site-specific and not easily determined, which hampers the development of proper management tools and guidelines. A two-dimensional soil-water balance model combined with a crop growth model was parameterized and validated, and used to investigate DM and water use of Thuja occidentalis Brabant in a field trial under non- and drip irrigated conditions. Measured leaf DM and leaf area index (LAI) were not affected by irrigation but irrigation increased stem DM and the specific leaf area. Simulated DM and LAI were in good agreement with the measurements. Simulated pressure head followed the measured pressure head, although models performance was better under dry than under wet conditions. Simulation experiments indicated that increasing irrigation threshold levels increased DM production and leaching relatively to no irrigation, when the irrigation threshold level was measured at 0.25m depth