The 2012 ASHS Annual Conference

Growth and water use during pot-in-pot production of birch (Betula nigra) was compared between two fiber containers  (Kord® Fiber Grow  and Western Pulp) and a standard black plastic container (GL2800, Nursery Supplies®^, Inc.). The experiments were conducted in KY, MI, MS, and TX.  Birch bare root liners were planted in mid-June 2011 into seven gallon containers filled with 85 pine bark: 15 peat (vol/vol). The containers were arranged in a completely randomized design with eight replications.  A GL6900 (15 gallon) container served as the socket pot. Bubble wrap was used to fill the gap between the production and socket pot for all the container types.  Copper-treated paper or fabric was placed between the production and socket pot to prevent roots from escaping the production container. Substrate moisture content was determined with a theta probe (ML2, Dynamax, Inc.). Irrigation was applied to replace 100% of daily water use.  Irrigation was delivered with one Tornado ray jet emitter, ~6 gph (Plastro Irrigation Systems, Ltd.) per container. Depending on location, there was a two- to three-fold increase in plant height during the four month study period. Plant caliper was found to increase by approximately 6 mm in all locations. The increase in plant height, caliper and/or plant growth index was not influenced by container type in any location. Daily water use was similar among the container types with an average water use of 2350 ml/day in Kentucky and 1480 ml/day in Michigan during August 2011. Water usage responded more to daily weather conditions than to container type in all the locations. Inspection of the fiber containers in March 2012 did not show any root outgrowth and the visual and tactile evaluation indicated that the side wall and bottom of the containers were intact and appeared to be suitable for use in the second year of the study. In conclusion, our initial findings indicate that there was no impact of fiber containers on plant growth and daily water use compared to standard plastic containers in pot-in-pot production. A second growing season will evaluate these same parameters under greater transpiration demand and root intrusion as the birch plants develop. The physical characteristics of the containers will also be evaluated at the termination of the study in October 2012.