Field-Grow Fabric Containers do not Affect Transplant Survival or Establishment of Green Ash

Materials and Methods

Green ash trees were grown under nursery conditions for two years in 30 cm diameter by 30 cm deep FGFC (Root Control, Oklahoma City, OK) containing field soil or field soil amended with 25 percent (by volume) peat, 4.7 kg/m³ 18 N-2.6 P-10 K slow release release fertilizer (Osmocote, Grace-Sierra, Milpitas, CA), 1.2 kg/m³ hydrophilic gel (Hydrosource, Western Polyacrylamide, Castle Rock, CO), peat + hydrophilic gel, peat + slow release fertilizer, or hydrophilic gel + fertilizer (5). The trees were harvested and transplanted into a Norge loam (fine-silty, mixed, thermic Udic Paleustolls) soil at the same site at Stillwater, OK or into a Haynie very fine sandy loam (coarse-silty, mixed calcareous, mesic typic Udifluvents Entisols) soil at Manhattan, KS. Root bags were removed at the time of transplanting. Control trees were grown without root restriction in the same field. The control trees were balled and burlapped with ball diameters of approximately 36 cm, as recommended by the American Association of Nurserymen (1), and transplanted with the burlap intact around the root ball. Plantings were completely randomized with eight treatments and eight replicates per site. Trees were planted at both sites on November 21,1990, and remained in the field for two growing seasons in Oklahoma and for one year in Kansas before harvesting.

The trees at both sites received overhead sprinkler irrigation as needed. The trees transplanted in Oklahoma were fertilized with 227 kg/ha N as urea (43-0-0) broadcast over the entire study area each spring, while plants in Kansas received 112 kg/ha N as ammonium nitrate (33-00) in bands in April. Weed control was accomplished through an annual application of (2-chloro-N-(2-ethyl-6 methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide) (metolachlor) in Oklahoma or (3,5-dinitro-N⁴, N⁴-dipropyIsuIfa-nilamide)(oryzalin) in Kansas and periodic hand cultivation.

Plant heights and calipers at 30 cm above the soil surface were measured monthly during 1991 and three times during the growing season beginning in mid-April (bud break) and ending in October (leaf abscission) in Oklahoma. Trees in Kansas were measured at the time of planting and at harvest. Canopy width was measured at the widest point. Upon completion of the study, the Oklahoma plants were harvested with a 76-cm diameter tree spade (Vermeer TS30, Baltimore, MD). The root balls were power washed and small (< 1cm) and large (> 1 cm) diameter roots were counted. Leaves, stems, and roots were separated and oven dried at 45°C for seven days before weighing. Analysis of variance procedures and Tukey’s w Procedure (8) were used to determine differences among the treatments.

Results and Discussion

All transplanted trees survived in both locations. There was no difference in short-term post transplanting height orcaliperincrease, regardless of production or harvest treatment, at either location (Table 1). There were also no differences in canopy width, leaf, stem, or root dry weight, or number of large (> 1 cm) or small (< 1 cm) roots, regardless of production treatment, for plants transplanted in Oklahoma (Table 2). Although root numbers did not significantly differ among the treatments, roots of plants in the FGFC tended to circle similar to those produced in container nursery production (Figure 1).

Previous authors speculated that a large majority of the root system is lost when a tree is balled and burlapped(9). The extent of retained root system is proportional to ball size and age of the plant at transplanting. One supposed advantage of the FGFC is that most of the root system is retained during transplanting. A balled and burlapped tree, therefore, would place much of its photosynthetic energy into root regeneration immediately following transplanting, at the expense of plant height. This has been shown with transplanted holly (//ex sp.) (7). Therefore, a tree produced in a FGFC might establish and initiate stem growth more rapidly than a balled and burlapped tree. More rapid establishment has been attributed to higher concentrations of leaf and root carbohy-drates of plants grown in FGFC (2). Results of this study, however, do not support this premise. Growth rates of balled and burlapped trees during the first and second season after transplanting equaled the FGFC trees. Production in field bags with or without amendment with peat, gels, or fertilizer did nothing to enhance stem or caliper growth.

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Figure 1.

Root system from a balled and burlapped tree (A) and a tree grown in FGFC (B) showing circling of the root system in the FGFC. Both root systems were approximately 76 cm in diameter.

Short term growth rates after transplanting are indicative of “establishment,” that is, successful growth of roots into native soil and root function. There were no differences in number of roots, or any stem growth parameter resulting from production or harvest method (Figures 1A and 1B).

Further research is needed to demonstrate advantages of FGFC in the production of more difficult to transplant species; however, there appears to be no real benefit to using FGFC when producing easily transplantable materials such as green ash.