Influence of Irrigation Method and Container Type on Northern Red Oak Seedling Growth and Media Electrical Conductivity

Container production of hardwood seedlings has not been extensively practiced. Efficient nursery production of hardwood seedlings in containers can be limited by formation of a broad foliar canopy, which limits irrigation uniformity. This study was established to investigate suitability of subirrigation, a method of irrigating seedlings from the container base that relies on rise of water through capillary action, for production of broad-leaved hardwood seedlings. Northern red oak (Quercus rubra L. [Fagaceae]) seeds were sown into 4 container types, and seedlings were grown in a controlled greenhouse environment under either traditional overhead irrigation or subirrigation. Media electrical conductivity (EC) was measured at container depths of 1, 5, and 10 cm (0.4, 2, and 4 in) after 57 d. Subirrigated seedlings had significantly higher EC at each depth compared with overhead irrigated seedlings, with a trend of decreasing EC with increasing measurement depth. A significant container type x irrigation method interaction suggested potential for toxic EC levels in some subirrigated containers, which can be alleviated by periodic leaching using clear water to dissipate salts from the top 1 cm (0.4 in). At the end of the growing period, seedling height and root-collar diameter were not influenced by irrigation method or container type, indicating that subirrigation is suitable for hardwood seedling production.