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Commonly used planting techniques and soil amendments were compared to determine their effect on root growth, shoot growth, and drought tolerance of 2.5 cm caliper Acer rubrum. Study I: Trees were planted on 6 April 1992 into holes backfilled with 1) native soil, 2) 50% aged pine bark: 50% native soil, 3) 50% Mr. Natural™:50% native soil, or 4) 100% Mr. Natural™. Mr. Natural™ consists of granite sand, expanded shale, and composted poultry litter. After two years, no differences in growth or survival existed. Study II: On 8 April 1992, trees were planted in 1) unamended planting holes, 2) tilled planting beds, or 3) tilled and pine bark-amended planting beds. Five months after planting, the root growth in the tilled and tilled-amended beds did not differ, but both had more root growth than planting holes. Amendment-induced nitrogen deficiency reduced shoot growth of the tilled-amended treatment during the first year. After two years, the planting hole treatment exhibited the least shoot growth, while shoot growth of tilled and tilled-amended treatments did not differ. StudyIII: Selected trees in study II were drought stressed for 8 weeks beginning 4 August 1993. No differences in relative leaf water content among treatments were observed Results suggest that native soil should be used as backfill in planting holes; however, tilling a planting bed increases root and shoot growth compared to planting in a hole. Amending beds with pine bark did not increase growth or drought tolerance.
Abstract
The high variability in physiologically different stages of leaves and susceptibility of pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars to the pecan scab [Cladosporium caryigenum (Ell. et Lang) Gottwald] fungus prompted an evaluation of phylloplane-associated substances (PASs) that influence fungal conidia germination. Germination of conidia was evaluated in several TLC fractions derived from water or dichloromethane leachates of the phylloplane of pecan leaves. Reciprocal tests of pecan scab conidia isolated from ‘Schley’ and ‘Stuart’ against phylloplane leachates from both ‘Schley’ and ‘Stuart’ were conducted. Several PASs proved to have either inhibitory, neutral, or promotive effects on conidia germination. 5-hydroxy-1,4-napthoquinone (juglone) was identified as one such substance and was observed to be a strong inhibitor of conidia germination, but had no effect on colony growth or sporulation. The susceptibility of pecan foliage to pecan scab appears to be partially dependent on phylloplane composition.
Container-grown Viburnum plicatum var. tomentosum `Mariesii' were planted in tilled beds and tilled beds amended with aged pine bark. After transplanting, plants were fertilized at three different rates: no fertilizer, 18.4 g of N m-2, and 36.8 g of N m-2. A 31 day drought was begun 73 days after planting. Fertilization of tilled plots induced ammonium toxicity, which caused a linear reduction in leaf area, shoot dry weight, and root dry weight. Fertilization of amended plots had no effect on shoot growth but reduced mot growth by 54%; thus, amendments ameliorated ammonium toxicity. Between 10 and 28 days after beginning the drought, plants in unfertilized-amended plots maintained higher relative leaf water contents (RLWC) and relative leaf expansion rates (RLER) than plants in unfertilized-tilled plots. Amendment induced nitrogen deficiencies contributed to the increased drought tolerance of plants from unfertilized-amended plots. Since fertilized plants developed symptoms of ammonium toxicity, we were unable to determine if increasing fertility would counteract the drought tolerance conferred by pine bark soil amendments.
Increasing demand for groundcover plants and increasing consumer preference for more sustainable products encourage nursery crop producers and landscape management companies to assess efficiency and sustainable practices. Ajuga reptans ‘Bronze Beauty’ and Sedum kamtschaticum ‘Variegatum’ were grown in standard plastic containers or plantable containers (Ellepot and SoilWrap) and 12- or 18-count flats. These production alternatives were presented in personal surveys of commercial industry personnel and consumers to determine their willingness to pay for these attributes. A conjoint analysis revealed an affinity for both groups to purchase flats of groundcovers and preferred sedum over ajuga. Commercial buyers from larger companies were more likely to purchase plantable containers than those from smaller firms. Generally, flats of Ellepots were preferred over flats of SoilWraps and 18-count over 12-count flats by commercial buyers. Price had a negative impact on consumer willingness to pay. Consumers revealed no specific preference for the plantable containers, although preference for plastic containers declined with age and presence of children at home.
Container-grown Viburnum plicatum Thunb. var. tomentosum (Thunb.) Miq. `Mariesii' were planted in unamended planting holes, tilled plots, and tilled plots amended with aged pine bark. A 36-day drought was initiated 108 days after planting. Amending induced N deficiencies, reduced shoot growth, and increased root growth. Plants harvested from tilled and planting-hole plots at drought initiation had 63% and 68% more dry weight, respectively, than plants from amended plots. Between 8 and 19 days after drought (DAD) initiation, plants from tilled plots maintained higher relative leaf water content (RLWC) than plants from planting holes. Plants in amended plots maintained higher RLWC than both other treatments between 7 and 33 DAD. Amended and tilled treatments had higher relative leaf expansion rates (RLERs) than the planting-hole treatment 8, 11, 13, and 15 DAD. As the drought lengthened, plants in amended plots maintained higher RLERs than plants in tilled plots. While plants in pine bark-amended plots were more drought tolerant than those in tilled plots, it is unclear if increased drought tolerance was caused by the improved rooting environment or N deficiency.
This review was conducted to synthesize current knowledge, learn producer and Extension specialist perspectives, and identify gaps in understanding of the role of soil health in sustaining production in high tunnel (HT) systems. This synthesis includes findings from scholarly resources related to soil health in HTs, including research and Extension-based literature, perspectives from experienced HT producers and technical assistance providers, and the direct observations of a broad network of university research and Extension personnel working with HTs. Findings are intended to identify knowledge gaps and additional research and Extension resource needs of greatest priority to the HT producer community and technical assistance providers that support them at the time of publication. A review of 68 research articles and 58 Extension resources was conducted. Focus group interviews were conducted with small groups of experienced HT farmers in four regions of the eastern half of the United States, with in-depth farm case studies conducted in individual farmers in three of these regions. Growers across regions identified soil fertility management, soilborne diseases, soil compaction, and lack of consistency of soil analyses specific to HTs as the greatest soil-related challenges to HT production. Research and resources for technical assistance providers on mitigation strategies to remediate yield-limiting HT soil conditions, such as excessive soil salinity and high pathogen populations, were also lacking. As such, process-based research on techniques such as leaching, soil steaming, solarization, and anaerobic soil disinfestation in tunnels that consider short- and long-term costs, benefits, and effects on soil and plant productivity should be prioritized in the future when considering the impact of HT production on soil health. Interviews also indicated a need for networking opportunities for technical assistance providers across agencies (e.g., Natural Resources Conservation Service, Extension, nongovernmental organizations). Despite a high and increasing rate of adoption, there is currently a lack of information about maintaining HT systems. Given that HTs play a critical and growing economic role for specialty crop growers throughout the eastern United States, comprehensive intervention across the research–Extension spectrum to sustain productivity in HT systems is recommended.