Irrigation and nitrogen use efficiency of Thuja occidentalis grown on sandy soils

A combined conifer growth - soil water and nitrogen balance model was calibrated to simulate dry mass production and partitioning, water and nitrogen demand and nitrogen losses for Thuja occidentalis grown for two years on a sandy soil. Light interception was successfully described by the row-of-cuboids method. A diffusion model was used to describe fine root growth. The combined model was used to explore nitrogen losses under irrigation and fertilization strategies for optimal dry mass production. Irrigation was frequently necessary for optimal dry mass production and depended highly on the actual weather conditions. The recommended fertilizer applications were sufficient. Nitrogen losses always exceed the European nitrate N-limit in the year of planting and by 80% in the second growing season when optimal irrigated and fertilized for dry mass production. Therefore, additional measures are necessary to develop conifer cropping systems on sandy soils within the framework of the EU nitrate-N limit.