Browsing by Author "Fields, Jeb S."
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- Physical and Hydraulic Properties of Commercial Pine-bark Substrate Products Used in Production of Containerized CropsAltland, James E.; Owen, James S. Jr.; Jackson, Brian E.; Fields, Jeb S. (2018-12)Pine bark is the primary constituent of nursery container media (i.e., soilless substrate) in the eastern United States. Pine bark physical and hydraulic properties vary depending on the supplier due to source (e.g., lumber mill type) or methods of additional processing or aging. Pine bark can be processed via hammer milling or grinding before or after being aged from <= 1 month (fresh) to >= 6 month (aged). Additionally, bark is commonly amended with sand to alter physical properties and increase bulk density (D-b). Information is limited on physical or hydraulic differences of bark between varying sources or the effect of sand amendments. Pine bark physical and hydraulic properties from six commercial sources were compared as a function of age and amendment with sand. Aging bark, alone, had little effect on total porosity (TP), which remained at approximate to 80.5% (by volume). However, aging pine bark from <= 1 to >= 6 months shifted particle size from the coarse (>2 mm) to fine fraction (<0.5 mm), which increased container capacity (CC) 21.4% and decreased air space (AS) by 17.2% (by volume) regardless of source. The addition of sand to the substrate had a similar effect on particle size distribution to that of aging, increasing CC and D-b while decreasing AS. Total porosity decreased with the addition of sand. The magnitude of change in TP, AS, CC, and D-b from a nonamended pine bark substrate was greater with fine vs. coarse sand and varied by bark source. When comparing hydrological properties across three pine bark sources, readily available water content was unaffected; however, moisture characteristic curves (MCC) differed due to particle size distribution affecting the residual water content and subsequent shift from gravitational to either capillary or hygroscopic water. Similarly, hydraulic conductivity (i.e., ability to transfer water within the container) decreased with increasing particle size.
- Surveying North American Specialty Crop Growers' Current Use of Soilless Substrates and Future Research and Education NeedsFields, Jeb S.; Owen, James S.; Lamm, Alexa; Altland, James; Jackson, Brian; Oki, Lorence; Samtani, Jayesh B.; Zheng, Youbin; Criscione, Kristopher S. (MDPI, 2023-08-31)Many specialty crop growers are transitioning high-value crops from in-ground production to soilless culture due to the diminishing availability of fumigants, increasing pest pressure, extreme weather, and the need for flexible production practices. The objective of this study was to determine the research and educational needs of specialty crop growers who are transitioning to soilless substrates. North American growers were surveyed using an online instrument that incorporated Likert-type statement matrices, open-ended questions, and demographic questions. Additionally, two virtually led focus groups were conducted to further expand upon the quantitative findings with descriptive data. Respondents indicated the most important factors in considering whether to adopt soilless substrates were improving, managing, and reducing overall plant quality, disease management, and crop loss, respectively. The most important research needs were understanding the effects of substrates on crop quality and uniformity, fertilizer management, and economic costs and benefits/return on investment. In both the grower survey and focus groups, crop quality and uniformity were among the highest-scored responses. Food safety, disease and pest management, consumer perception, substrate disposal-related issues, transportation, and return-on-investment were also identified as important factors when considering soilless substrates.
- Understanding Soil Moisture Sensors: A Fact Sheet for Irrigation Professionals in VirginiaSample, David J.; Owen, James Stetter, 1975-; Fields, Jeb S.; Barlow, Stefani (Virginia Cooperative Extension, 2016-09-23)Discusses the use of sensors to monitor soil water, and evaluates several types.