Arboriculture & Urban Forestry 44(4): July 2018 were irrigated using a drip irrigation system to apply 5.7 L of water every other day. Height and caliper (measured at 15 cm above the con- tainer growing substrate surface) were mea- sured monthly, from June to September 2010. Landscape Planting In October 2010, 27 trees (three single-plant replications of three container types to be har- vested over three years) were planted into a Poa pratensis (Kentucky bluegrass) lawn. The soil type was a sandy clay loam, with a pH of 7.7, EC of 0.4 mmhos/cm, and 6.4% organic matter. Soil test results prior to planting (Colorado State University Soil, Plant, and Water Testing Labo- ratory; data not shown) indicated that all nutri- ents were present at levels adequate for turf and tree growth, so supplemental fertilizer was not added at planting. At the time of removal from containers, root balls were scored for matting, circling roots, and root ball integrity (Table 1). Trees were planted on 1.8 m × 1.8 m spacing, in a randomized complete block design, with three replicates and trees per container type and replication. Trees were planted using best management practices in saucer-shaped holes approximately three times as wide as the root ball. Root balls were not shaved or washed prior to planting, but the bottom and sides of each root ball were scored using box cutters, and any visible circling roots were hand pruned. Trees were planted at 2.5 cm above soil grade. Trees were watered and mulched with a 5 cm depth of organic mulch (shredded bark) measuring 1.8 m in diameter, centered on the tree. Mulch was not applied over the top of the root ball. Mulch was kept free of weeds and grass with occasional applications of glyphosate. Trees were not staked at planting. Following plant- ing, trees and turf were irrigated with an auto- mated irrigation system (to prevent turf stress; 2.5 to 5 cm/week). The turf was mowed twice weekly (5 cm mowing height), during periods of active growth, and fertilized twice yearly with 48.8 kg N/ha. Throughout the study, trees were pruned only to remove broken branches. Tree height and caliper were measured monthly during the 2011 to 2013 growing seasons. New twig growth, measured on one randomly 167 selected branch on the north, south, east, and west sides of trees was measured in autumn of each growing season. Total leader growth was measured from the previous point of growth to the tip of the current season’s growth. Table 1. Root ball characteristics of nursery-grown (six months) Chanticleer pear in three container types (2010). Root ball integrityz Black plastic Root Pouch Smart Pot 4.9 4.9 4.3 ns with 1 being many matted roots). x Bottom root ball mattingy 1.5c 3.0b 4.0a *** Circling rootsx 2.2c 3.7b 4.4a ** from the container; scale of 1–5, with 5 holding together well). y z Root ball integrity (how well the root ball held together when removed Root ball matting (matting on the bottom of the root ball; scale of 1–5, Circling roots (frequency, based on a scale of 1–5; with 1 being many circling roots). Notes: Means within a column for each measurement followed by different letters are significantly different at P = 0.05 using Tukey’s LSD test; ns = not significant; single asterisk (*) indicates P = 0.05–0.01; double asterisk (**) indicates P = 0.01–0.001; triple asterisk (***) indicates P ≥ 0.001. Harvest Methods Tree roots were removed from the ground in autumn of 2011, 2012, and 2013 (nine trees each year; three from each container type) by air spading, and also using water to loosen roots that were still attached to the soil. At har- vest, all leaves were removed and oven-dried at 70°C for one week to determine total leaf dry weight. Root balls were washed to remove soil. Branches and trunk were separated from the root ball, weighed fresh, and then oven-dried at 70°C for one week to obtain dry shoot weight. Each excavated root ball was placed on a its original container width and template of pruned to separate roots that had grown beyond the original root ball after plant- ing. Roots were separated into two groups (inside and outside of the original root ball), oven-dried, and weighed. Following drying, roots were separated into fine (<2.0 mm) and coarse (≥2.1 mm) roots and weighed again. All data were subject to analysis of vari- ance (Version 9.4, SAS Institute Inc., Cary, North Carolina, U.S.) using a fixed effect model. Where significant effects were indicated, means were separated using Tukey’s LSD test. ©2018 International Society of Arboriculture
July 2018
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