The effects on posttransplant growth of seedlings from nursery containers are well studied (Amoroso et al., 2010; Arnold and McDonald, 2006; Gilman et al., 2016; Struve, 1993). Container-grown plants may develop deformed roots during the nursery stage (Gilman et al., 2003; Lindström and Rüne, 1999), leading to long-term growth issues (Balisky et al., 1995; Lindström and Håkansson, 1995) that range from plant instability caused by uneven distribution of roots (Nichols and Alm, 1983) to reduction in shoot growth and decline of the trees (Ortega et al., 2006). In some cases, root malformation may lead to the death of the plant.
Survival and the resilience of nursery seedlings to transplant stress depends on their ability to produce a root system rapidly that is capable of invading the new soil. There are possible ways to reduce transplant stress for container-grown plants. One treatment is to prune the taproot. When kept in the container for an extended period of time at the nursery, taproots circle around when they reach the bottom of the container. Establishment becomes a challenge for roots in such conditions (Amoroso et al., 2010). The malformation can be corrected by pruning the deformed root to allow a better root system to form. However, remediation of a deformed root by pruning may exacerbate transplant shock (Struve, 1993).
Another treatment is to remove the potting media. The pH level, soluble salts, and carbon-to-nitrogen ratio contained in the potting mix should meet the requirements of the plant (Ingram et al., 1993). When the potting media meet the desirable chemical properties of the plant, the root growth in the less desirable soil around the plant may be lessened. Therefore, it might be advantageous to remove the potting medium before planting so the roots acclimate to the new soil environment more rapidly. Lipe et al. (2018) recommend using a hose to wash off the outer inch of potting medium.
Pecan trees are native to the southern region of the United States and grow well in a large variety of soils. As seedling trees, pecan trees are often grafted with shoots from another donor (typically a tree with an outstanding quality of nuts). With container-grown trees, industry practice varies with regard to root pruning, root disturbance, and potting medium removal. The three planting methods for pecan trees are 1) container tree planted straight from the container with no root pruning and no disturbance (container as is), 2) container tree with a pruned taproot and minimal disturbance of the root ball (pruned), and 3) container tree with a pruned taproot and all potting medium removed (no potting medium).
No study has investigated the impacts of these planting alternatives on the growth and survival of pecan trees. There is no consensus on the best way to plant pecan trees. The nursery providing the trees recommended planting as is. Wells et al. (2015) recommend pruning the taproot with minimal disturbance. Our final treatment is meant to simulate the planting of bare-root trees, which is also a common planting method. The objective of this experiment was to determine the effects of the three alternative methods of transplanting on pecan tree growth and survival.
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