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Two experiments tested the effects of root pruning on growth during first-season production of pin oak (Quercus palustris Muenchh.). Experiment one tested the effect of root pruning developing radicles at 5, 10, or 15 cm (2, 4, or 6 inches) below the substrate surface. After 11 weeks, total root length was not affected by root pruning, but root-pruned seedlings had more main lateral [>2-mm (0.08-inch) diameter] roots than those that were not root pruned. Shallow pruning increased the number of main lateral roots. Experiment two tested the effect of initially producing plants in different-depth bottomless containers [5, 10, 15, or 20-cm (2, 4, 6, or 8-inch) depth] on growth after transplanting to #2 [6 L (1.6 gal)] containers. Shoot and root growth in #2 containers were lowest when plants were originally produced in 5-cm-deep containers. Plants with the greatest height and highest root:shoot ratios were obtained when plants were grown initially in 10-cm-deep containers. Predicted optimum depth of bottomless containers from regression equations ranged from 11.3 cm (4.5 inches) to 14.2 cm (5.5 inches) for the different growth parameters measured. The importance of these findings are: Pruning developing radicles of pin oak seedlings increases the number of main lateral roots but not overall root length. Growers can maximize growth in #2 containers by initially growing in 10-cm-deep bottomless containers before transplanting to #2 containers.

A survey, focusing on the use of irrigation and fertilization best management practices (BMPs), was designed and released to Virginia nursery and greenhouse growers. The objectives of the survey were to determine the most widely used BMPs, assess the reasons for their use, and identify barriers to BMP adoption. The survey was distributed in person, via e-mail attachment, or link to 357 Virginia growers in 2016 with 60 respondents. Survey results demonstrate that the most widely used BMPs in Virginia included irrigation scheduling, integrated pest management (IPM) implementation, altering irrigation practices to optimize irrigation efficiency, controlled-release fertilizer (CRF) use, and plant need–based watering. Respondents selected environmental/resource savings as one of the most cited reasons behind BMP use for water, fertilizer, and runoff management. Cost was the most cited barrier to BMP adoption for all BMPs. Fertilizer management BMP implementation was primarily an economic decision. The value of determining the most widely used BMPs and impediments to BMP adoption is that we can 1) communicate this information to growers who currently do not employ BMPs to encourage BMP adoption and 2) subsequently inform the regulatory community of BMP use. Increased BMP use can boost the potential for mitigation of agricultural nutrient and sediment runoff into impaired waterways, including the Chesapeake Bay, and help growers increase efficiency of operation inputs, such as water and fertilizer resources, while potentially saving money.

Three experiments were conducted to determine the feasibility of using Biobarrier, a landscape fabric with trifluralin herbicide-impregnated nodules, of various sizes to prevent root escape of trees from the drainage holes of 56-liter containers in below-ground pot-in-pot (P&P) and above-ground Keeper Upper (KU) nursery production systems. In addition, side holes or slits were cut in some container walls to test the effect of Biobarrier on the prevention of circling roots. In Expt. 1 (P&P), Betula nigra L. `Heritage' (river birch) trees with no Biobarrier had root ratings for roots escaped through drainage holes that indicated a 5-fold increase in numbers of roots than for treatments containing Biobarrier. All Biobarrier treatments reduced root escape and resulted in commercially acceptable control. In Expt. 2 (KU), control and the Biobarrier treatment river birch trees (30 nodules) had commercially unacceptable root escape. In Expt. 3 (P&P), control and 10-nodule treatment Prunus × yedoensis Matsum. (Yoshino cherry) trees had commercially unacceptable root escape, but treatments containing 20 and 40 nodules resulted in commercially acceptable control. Biobarrier did not limit shoot growth in any of the experiments. The results of these experiments indicate that Biobarrier did not prevent circling roots, but sheets containing at least 8 or 20 nodules of trifluralin acceptably prevented root escape from drainage holes in the pot-in-pot production of 56-liter container river birch trees and Yoshino cherry trees, respectively.

Nursery and greenhouse growers use a variety of practices known as best management practices (BMPs) to reduce sediment, nutrient, and water losses from production beds and to improve efficiency. Although these BMPs are almost universally recommended in guidance manuals, or required by regulation in limited instances, little information is available that links specific BMPs to the scientific literature that supports their use and quantifies their effectiveness. A previous survey identified the most widely used water management, runoff, and fertilizer-related BMPs by Virginia nursery and greenhouse operators. Applicable literature was reviewed herein and assessed for factors that influence the efficacy of selected BMPs and metrics of BMP effectiveness, such as reduced water use and fertilizers to reduce sediment, nitrogen (N), and phosphorus (P) loads in runoff. BMPs investigated included vegetative zones (VZs), irrigation management strategies, and controlled-release fertilizers (CRFs). Use of vegetative buffers decreased average runoff N 41%, P 67%, and total suspended solids 91%. Nitrogen, P, and sediment removal efficacy increased with vegetative buffer width. Changes in production practices increased water application efficiency >20% and decreased leachate or runoff volume >40%, reducing average N and P loss by 28% and 14%, respectively. By linking BMPs to scientific articles and reports, individual BMPs can be validated and are thus legitimized from the perspective of growers and environmental regulators. With current and impending water use and runoff regulations, validating the use and performance of these BMPs could lead to increased adoption, helping growers to receive credit for actions that have been or will be taken, thus minimizing water use, nutrient loss, and potential pollution from nursery and greenhouse production sites.