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With the prospect of increasing regulation of water usage in container nurseries, irrigation system efficiency has become of prime importance to the nursery industry. In typical overhead irrigation, water losses of 75-90% are common. Cyclic, or intermittent, irrigation is a relatively new practice where a plant's daily allotment of water is broken up into a series of irrigation events. Recent research indicates that cyclic irrigation can increase irrigation efficiency by as much as 38% compared to irrigation applied once per day without adversely affecting plant growth. Another common problem in container nurseries is root-bound plants resulting from plants growing too long in a container or putting a vigorously rooting plant in a container that is improperly sized for the rapid growth of the roots. Root-bound plants are slower to establish following transplanting into a larger container or the landscape. Copper applied to the inner surface of containers is effective in reducing surface root development by chemically pruning roots of the plant as they encounter the container wall. Currently there are two copper treated containers available in the nursery industry, Spin-Out TM (Spin-Out TM, Lerio Inc. Mobile, Alabama) containers coated with copper hydroxide and Root Right TM (Nursery Supplies, Chambersburg, Pennsylvania) containers impregnated with copper chloride. The objectives of this project were to test the effects of cyclic microirrigation on growth of Atlantic white cedar and to evaluate the effects of two commercial container copper treatments on root growth. METHODS Seventy-two Atlantic white cedar (Chamaecyparis thyoides) were planted in 3-gallon containers in April 1998. Of the 72 plants, 24 were planted into Root RightTM containers, 24 were planted into Spin-Out TM containers, and 24 were planted into untreated containers. The medium used was an 80:20 mixture of pinebark:peat moss amended with 5 pounds of dolomitic limestone and 7 pounds of Osmocote 15-9-11 plus minors per cubic yard. Just after potting, ten randomly selected containers were saturated with water, allowed to drain for 20 minutes, and weighed to determine maximum water-holding capacity or “container capacity.” Containers were weighed 1 day later to determine the amount of water utilized by the plant or lost to evaporation (container capacity-weight after 1 day). The difference in the weights gave the approximate volume of water to apply on a daily basis. This volume was applied to the plants daily in one application, or the volume was divided into three or six equal applications. The volume of water applied was adjusted monthly throughout the growing season. Irrigation was applied through maxi-jet spray stakes. Height, canopy widths, caliper measurements, and root ratings were recorded monthly from April through November. RESULTS Plants under cyclic irrigation had a larger growth index [(height + width1 + width2 )/3 where width1 is at the widest point, and width2 is perpendicular to width1], and caliper than those plants watered once per day (Figures 1 and 2). There were no differences in growth between the two cyclic treatments (three and six times per day).
Container treatments had several effects on plant growth (Figures 3 and 4). Plants treated with copper had a lower root rating (less root-bound) than those plants grown in the copper-free containers. Plants grown in Spin-Out TM containers had a lower root rating than those plants grown in the Root Right TM containers. Plants grown in the copper-treated containers had a larger caliper than plants grown in copper-free containers.
In summary, this study shows cyclic irrigation to have a positive effect on growth of Atlantic white cedar. While Spin-Out TM containers were more effective at controlling root circling than Root Right TM containers, the Root Right TM container provided more root control than copper-free containers and effectively prevented the plant from becoming root-bound. |
