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Research is lacking on the impact of alternative reduced tillage (RT) systems on vegetable crop performance and soil quality, especially in organic production systems, where weed control cannot rely on synthetic herbicides. A 2-year field study was implemented in Aug. 2010 in Knoxville, TN, to evaluate cover crop–based systems for organic vegetable production either with or without spring tillage. Treatments, all organically managed, included 1) Till (+ACC), spring tillage of a winter cover crop with aboveground cover crop biomass (ACC) retained and soil covered by polyethylene mulch; 2) Till (−ACC), spring tillage of a winter cover crop with aboveground cover crop biomass (ACC) removed before tillage and soil covered by polyethylene mulch; and 3) RT system with no spring tillage and mechanically terminated winter cover crop residue on the soil surface. Vegetable crops of eggplant (Solanum melongena L.) and watermelon [Citrullus lanatus (Thunb.) Matsum. et Nakai] were planted in 2011 and 2012, respectively. Crop yield, cover crop biomass accumulation, soil N and C dynamics, and weed density were assessed. Marketable eggplant yield and marketable watermelon yield did not differ among treatments, but weed density was higher in the RT system. Measures of soil quality after 2 years of the study indicated that particulate organic matter-carbon (POM-C) and -nitrogen (POM-N) were highest in the RT treatment, a significant increase as compared with values at the beginning of the study. As a measure of the active fraction of soil organic matter, this indicates that the RT system may best maintain and improve soil quality in similar regional organic vegetable cropping systems. As indicated by measures of soil quality and crop yield, removal of aboveground cover crop biomass did not negatively impact the Till (−ACC) system as compared with the Till (+ACC).

The flavor attributes of cacao (Theobroma cacao) is becoming an important consideration in trade specifically for fine or flavor cocoa. In this market segment, flavor along with other physical attributes, not only contributes to the quality of a cocoa lot but also the price premium obtained. Past studies have shown evidence of pollen parent effects on yield, bean size, and pod characteristics, but its effect on flavor attributes is not clearly understood. An incomplete diallel mating design involving five cacao cultivars [West African Amelonado (WAA), Imperial College Selection (ICS) 1, Iquitos Mixed Calabacillo (IMC) 67, and two Trinidad Selected Hybrids (TSH) coded as CCL 200 and CCL 201] with widely differing flavor attributes were used to investigate the magnitude of female and male parent effects on key intrinsic flavor attributes. The seeds derived from pods arising from these pollinations were fermented, dried, and made into cocoa liquor according to standardized methods. Flavor evaluations were carried out by a trained sensory panel for nine flavor attributes with five repetitions and hidden flavor reference controls. The study was conducted over two cocoa crop years. The results failed to detect dominant xenia effects for important ancillary flavor attributes (i.e., cocoa flavor, acidity, fruitiness, and floral flavors), but showed significant female parent effects for cocoa and floral flavors. Small but inconsistent male parent effects were seen for astringency. Lack of xenia effect for the major flavor attributes implies that the flavor quality of cocoa beans is determined principally by the genotype of the female parent.

Abstract

Seasonal changes in soluble carbohydrates of Fraser fir [Abies fraseri (Pursh) Poir.] needles were monitored in Fall 1984, Spring 1985, and Fall 1985 through Spring 1986. Raffinose concentration increased in the fall and decreased in the spring. There was a 23-fold increase in raffinose concentration from Aug. 1985 to Jan. 1986. Sucrose concentration varied from fall to spring with the lowest concentration occurring in February. Postharvest needle abscission from harvested branches held 6 weeks without water was inversely correlated with raffinose concentration at the time of harvest. Diurnal fluctuations in soluble carbohydrates were monitored on 12 July and 26 Oct. 1985. Raffinose concentration fluctuated slightly on both dates with a decrease during the dark period. On 12 July, sucrose increased during the day and decreased at night, whereas hexoses decreased in the day and increased at night. No significant diurnal changes in sucrose or hexose were evident on 26 Oct. Controlled-environment studies at 24° (day)/18°C (night), 18°/12°, and 12°/6° showed that most of the raffinose accumulation was due to low temperature; the remainder to short days. Postharvest needle loss was lowest in plants with high needle raffinose concentrations resulting from the 12°/6° temperature. Storage without water resulted in significant postharvest needle loss for shoots from plants preconditioned with 24°/18° and 18°/12°, but not for those exposed to 12°/76°. Compared to long days, plants preconditioned with short days lost fewer needles following harvest.

Afield study of organic production of tomato (Lycopersiconesculentum Mill.) in high-tunnels was conducted in 2004. `Mountain Fresh' was transplanted 31 Mar.; `Ultra Sweet' and `Sun Leaper' were transplanted on 21 July. The primary objective was to determine the feasibility of obtaining two crops of fresh-market tomatoes by starting plants 4–8 weeks earlier than the average last spring-killing frost, and extending the growing season 4–6 weeks past the average first fall-killing frost. Plants were started at weekly intervals for 4 weeks in both seasons. Data and observations were recorded on the yield of marketable fruits, plant growth and development, and plant health. Other objectives were to evaluate: 1) the benefits of using a selective UV-blocking film on plant growth and development, disease events; and 2) compost amendments on soil improvement and disease control. Major cultural challenges included water management, soil texture/drainage, prevention of chilling injury, plant support, and adequate ventilation. Major disease/pest challenges involved stalk rot caused by Sclerotinia sclerotiorum in the spring, powdery mildew in spring and late summer, Alternaria and Septoria leaf blight in late summer, and aphids, tomato hornworm, corn earworm, and beet army worm also in late summer. In addition, macrofaunal intrusions by fox, mice, and birds occurred sporadically. Poor drainage and stalk rot in the spring necessitated relocating the tunnels to an uninfested site with better drainage. The fall crop yielded high numbers of marketable quality fruits, well beyond the 15 Oct. average killing frost date. The results suggest that with improved management, there is a considerable potential for profitable extended-season production of organic tomatoes in this region.

Anaerobic soil disinfestation (ASD) is a biologically based, non-fumigant, pre-plant soil treatment developed to control soilborne plant pathogens and plant-parasitic nematodes in specialty crop production systems. Soil treatment by ASD includes the incorporation of a labile carbon (C) source, tarping with plastic, and irrigation of the topsoil to saturation (5 cm irrigation) to create conditions conducive to anaerobic decomposition of the added C source. A field study was implemented beginning in Fall 2010 and repeated in the same plot locations in Fall 2011 in Knoxville, TN, to evaluate ASD. Soil properties, weed and Rhizoctonia solani population dynamics, and crop performance were evaluated after ASD treatment with several potential C sources for ASD before production of fresh-market tomato (Solanum lycopersicum L. ‘Red Defender’) and red bell pepper (Capsicum annum L. ‘Red Knight X3R’). Treatments included: 1) untreated control; 2) mustard seed meal (biofumigant control); 3) ASD with dried molasses; 4) ASD with soil-incorporated Indian mustard (Brassica juncea L.), white mustard (Sinapis alba L.), and arugula (Eruca sativa Mill.) cover crop with molasses added at cover crop incorporation; 5) ASD with soil-incorporated Indian mustard, white mustard, and arugula cover crop; 6) ASD with soil-incorporated cereal rye (Secale cereale L.) cover crop with molasses added at cover crop incorporation; and 7) ASD with soil-incorporated cereal rye cover crop. Accumulated soil anaerobic conditions were significantly greater than the untreated control in all ASD treatments except the ASD mustard/arugula treatment. Although not related to accumulated anaerobic conditions, populations of R. solani were lowest and equivalent to the biofumigant control for ASD cereal rye and ASD mustard/arugula treatments. Differences in weed populations and soil inorganic nitrogen among treatments were limited. Yield of bell pepper and tomato did not differ among treatments, which may have been partly the result of the low pest pressure observed at the site over the 2 years of the study.

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.