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Open access

George E. Boyhan, Cecilia McGregor, Suzanne O’Connell, Johannah Biang and David Berle

There is a dearth of information on pepper (Capsicum annuum) variety production under organic conditions; therefore, a randomized complete block designed experiment of 13 pepper varieties were evaluated in 2016 and 2017 using organic production practices on land managed organically for the 6 previous years. Total yield, graded yield, and early yield were the main factors of interest. There were by-year interactions, so the data were analyzed separately for each year. All of the peppers evaluated except for ‘Sweet Chocolate’ were bell pepper types. The average total yield was 1229 and 1754 boxes/acre (28 lb/box) in 2016 and 2017, respectively. There were no statistically significant differences for total yield or early total yield in 2016. In 2017, the top five highest yielding varieties were Aristotle X3R®, Gridiron, King Arthur, Flavorburst, and Blitz. With the exception of ‘Flavorburst’, all of these entries were among the highest yielding for fancy fruit (≥3 inches diameter and 3.5 inches length). The greatest early yield in 2017 included ‘Aristotle X3R®’, ‘Flavorburst’, ‘Touchdown’, ‘Islander’, and ‘Gridiron’. In 2017, early yields of fancy fruit greater than 100 boxes/acre included ‘Aristotle X3R®’, ‘Red Knight X3R®’, ‘Blitz’, and ‘Gridiron’.

Open access

Jacob C. Domenghini

Interest in organic vegetable gardening has increased in recent years. Organic growers are searching for alternatives to glyphosate for weed suppression. This study was conducted twice. Each data collection period lasted 132 days during the growing seasons of 2016 and 2017 in Richmond, KY. Treatments included application of glyphosate, vinegar [5% acetic acid (AA)], 20% horticulture grade vinegar (20% AA), 30% horticulture grade vinegar (30% AA), and a negative control. Treatments were applied in a factorial arrangement with two application periods (fall and spring or spring only). The percentage of weed cover within plots was evaluated visually with a 0–10 rating scale (0 = 0% weeds or 100% of the plot is dead; 5 = 50% weed growth; 10 = 100% of the plot is alive with weeds). All plots began the study with a rating of 10. After the initial treatment applications, visual ratings of the 5%, 20%, and 30% AA declined to a rating of 0 within 48 hours, whereas the glyphosate required 7 days (P = 0.05). Treatments were reapplied to part of the plots (subplots) in the spring when ≈50% of the plot had regrown with weeds. Glyphosate required 71 to 80.8 days to reach 50% regrowth and required only one retreatment. The 20% and 30% AA applications required three (2016) and four (2017) retreatments. Glyphosate has proven to be more effective at weed control in vegetable gardens when compared with vinegar, although 20% AA and 30% AA are viable alternatives.

Open access

Masahiro Toyoda, Yuko Yokota, Marni Barnes and Midori Kaneko

In modern society, stress reduction in the workplace is a pressing issue. Although many studies have been done on the psychological and physiological effects of indoor plants, the majority of them have been conducted in laboratory or quasi-office settings. The objective of this study was to verify the stress reduction effects of the presence of small indoor plants on employees in a real office setting. We investigated the changes in psychological and physiological stress before and after placing a plant on a worker’s desk. Sixty-three office workers at an electric company in Japan were the participants of this study. The participants were directed to take a 3-minute rest while sitting at their desk when they felt fatigue. There were two phases of the study: a control period without plants and an intervention period when the participants were able to see and care for a small plant. We measured psychological stress in the participants using the State-Trait Anxiety Inventory (STAI). As an index of physiological stress, the participants measured their own pulse rate throughout the study. STAI scores decreased significantly after the intervention period (P < 0.05). The ratio of the participants whose pulse rate lowered significantly after a 3-minute rest increased significantly during the intervention period (P < 0.05). Our study indicates that having opportunities to gaze intentionally at nearby plants on a daily basis in the work environment can reduce the psychological and physiological stress of office workers.

Open access

Christian T. Christensen, Lincoln Zotarelli, Kathleen G. Haynes and Charles Ethan Kelly

Solanum chacoense is a wild relative of potato (Solanum tuberosum) that is of interest because of its many desirable traits, but it exhibits variations in tuber dormancy across accessions. The objective of this study was to determine an appropriate gibberellic acid (GA3) concentration and soak time treatment to encourage sprout development across four accessions of S. chacoense (A, B, C, and D) from the 174 accessions of the U.S. Department of Agriculture Potato Genebank. Twelve treatments were created by using four concentrations of GA3 (0, 50, 100, and 150 μg·mL−1) across three soak periods (5, 45, and 90 minutes). Small (average weight, 1.4 g), medium (2.6 g), and large (5.6 g) tubers were distributed among all treatments. Percentage of tubers sprouted, time to sprouting, sprout length, and sprout number per tuber were analyzed to determine the effectiveness of GA3 treatments on dormancy breaking. GA3 concentrations of 50, 100, and 150 μg·mL−1 partially broke dormancy within accessions B and C. None of the tested treatments were effective for breaking dormancy in accession D within 46 days after treatment. Accession A showed weaker dormancy, thus producing a similar percentage of sprouted tubers across all GA3 treatments. Soak time had no significant effect on all parameters measured. Larger tubers produced greater sprout number per tuber and percentages of sprouted tubers. Soaking tubers in 50 μg·mL−1 of GA3 may be an effective treatment for S. chacoense accessions with mild dormancy, but alternative methods to break dormancy may be required for S. chacoense accessions with stronger dormancy.

Open access

Ronald C. Stephenson, Christine E.H. Coker, Benedict C. Posadas, Gary R. Bachman, Richard L. Harkess, John J. Adamczyk and Patricia R. Knight

Due to difficulty in monitoring insect pests, applications of insecticides are frequently conducted on a calendar schedule. However, seasonal variability in pest populations leads to these calendar schedules sometimes being inaccurate. Threshold-based insect management strategies, including use of thresholds with conventional pesticides and with use of organic pesticides only, were compared with a conventional calendar approach for yield, management cost, and production value of tomato (Solanum lycopersicum). Effect of cultivar was considered by inclusion of the long season cultivar Celebrity and the short season cultivar Early Girl Bush. These factors were compared for spring and fall seasons during two production years. Greatest total and marketable yields were obtained from use of conventional pesticides according to action thresholds. Use of organic insecticides according to thresholds did not affect yields in comparison with a calendar-based approach. Proportion of fruit rated unmarketable was greater with use of organic insecticides due to reduced efficacy and residual of control. Production costs for the organic threshold-based approach were greater due to increased number of insecticide applications required. Gross margin for both conventional and organic threshold-based insect pest management was greater than for the conventional calendar method. Increased economic return for conventional threshold-based management was due to increased yields. Increase in return for organic threshold management was based on premiums received for organically grown tomatoes. Adoption of conventional threshold-based insect pest management by small-scale producers has the potential to increase production efficiency and value, as well as increase environmental sustainability of production. Economic feasibility of organic production requires access to markets willing to pay significant premiums for organic produce. Further research to evaluate economic and yield impacts of production practices for small-scale farms is needed.

Restricted access

Camila P. Croge, Francine L. Cuquel, Paula T.M. Pintro, Luiz A. Biasi and Claudine M. De Bona

Antioxidants are compounds with varied chemical structures that are affected by biotic and abiotic factors. The objective of this study was to characterize and compare bioactive compounds and the antioxidant capacity of fruit from four blackberry cultivars produced under different climatic conditions. Ascorbic acid content, total polyphenols, flavonoids, monomeric anthocyanins and antioxidant activity of the fruit were evaluated, and high levels of bioactive compounds as well as antioxidant activity were observed regardless of the cultivar or growing location. The results showed that bioactive production is affected by the cultivar and environment. Furthermore, the antioxidant potential of the blackberry fruit depends on the total phenolics and anthocyanin.

Open access

Yuan Li, Arend-Jan Both, Christian A. Wyenandt, Edward F. Durner and Joseph R. Heckman

Although not considered an essential nutrient, silicon (Si) can be beneficial to plants. Si accumulator species such as pumpkin (Cucurbita pepo var. pepo) can absorb Si from soil. Si uptake may reduce plant susceptibility to fungal diseases such as cucurbit powdery mildew (Podosphaera xanthii and Erysiphe cichoracearum). We previously reported that wollastonite, an Organic Materials Reviews Institute–approved natural mineral, can increase soil Si level, increase soil pH, provide pumpkin plants with Si, and increase their resistance to powdery mildew. In this study, we examined the optimum application rate of wollastonite for pumpkins grown in pots and exposed to cucurbit powdery mildew. We confirmed that wollastonite has liming capabilities similar to regular limestone. Regardless of the application rates, wollastonite and limestone showed similar effects on soil chemistry and plant mineral composition. Pumpkin plants grown with the lower doses of wollastonite amendments (3.13 and 6.25 tons/acre) had the greatest tissue Si concentrations and demonstrated the greatest disease resistance. We conclude that wollastonite is a useful material for organic cucurbit (Cucurbitaceae) growers who want to increase soil pH and improve plant resistance to powdery mildew at the same time. Applying wollastonite at rates beyond the amount required to achieve a desirable soil pH for pumpkin production did not further increase Si uptake, nor did it further suppress powdery mildew development.

Open access

Tripti Vashisth and Taylor Livingston

Previous research has shown that Huanglongbing {HLB [causal agent Candidatus Liberibacter asiaticus (CLas)]}-affected sweet orange (Citrus sinensis) trees have a reduced root-to-shoot ratio, potentially due to the high rate of root death. The diminished root system cannot support the existing aboveground canopy and a cycle of imbalance begins. As a result, the tree enters into a continuous carbohydrate stress cycle and, eventually, the tree declines. Therefore, the goal of this study was to evaluate pruning as a strategy to adjust the root-to-shoot ratio to improve growth and productivity of HLB-affected trees. In Jan. 2015, a 3-year trial was initiated on a 14-year-old grove of ‘Hamlin’ sweet orange on Swingle citrumelo (Citrus paradisi × Poncirus trifoliate) rootstock that was symptomatic of HLB and produced less than 180 lb of fruit per tree. The four pruning treatments were as follows: 1) 0% pruning (no canopy removal), 2) 25% pruning (canopy removed), 3) 50% pruning (canopy removed), and 4) 80% pruning (canopy removed). In a split-plot design, two sources of fertilizer were evaluated in combination with the pruning: 1) conventional fertilizer [CNV (dry granular)] applied at 200 lb/acre nitrogen (N) in five split applications per year, and 2) controlled-release fertilizer (CRF) applied at 150 lb/acre N, split in three applications per year. Within each pruning treatment, half of the trees received CNV and the other half received CRF. The fertilizer treatments were applied in each of the 3 years; however, pruning was performed only once in the beginning of the experiment. The trees that were pruned produced new vegetative growth that looked healthy with no visual HLB symptoms (initially); however, the trees remained positive for CLas throughout the study as determined by quantitative real-time polymerase chain reaction. The 80% pruned trees grew vigorously over the course of 3 years but remained significantly smaller in canopy than control trees (0% pruning) for both CRF and CNV treatments. The 25% and 50% pruned tree canopies grew back and were similar in canopy size as 0% pruning (control) treatment by the end of year 2. At the end of the study, the use of CRF on 25% pruned trees resulted in a significantly higher leaf area index as compared with trees receiving CNV. A significant positive linear correlation was observed between canopy volume and root density; the root density decreased with intensive pruning. A significant positive correlation was also observed between canopy volume and yield, and a negative correlation between canopy volume and fruit drop. There were no significant increases in yield resulting from any pruning or fertilization treatments compared with controls (0% pruning). However, with the use of CRF, the amount of N and frequency of application were reduced. Overall, our results indicate that pruning did not improve the productivity of HLB-affected trees over the course of 3 years. Therefore, severe pruning is not a viable option to rejuvenate the HLB-affected trees.

Open access

Isaac T. Mertz, Nick E. Christians and Adam W. Thoms

Amino acids have been reported to improve turfgrass growth compared with mineral nutrition; however, amino acid catabolism in plants has not been well studied. A number of turfgrass fertilizers contain amino acids; however, some amino acids may be more effective additives in fertilizers than others. Three amino acids that could be effective nitrogen sources for plant growth are the branched-chain amino acids (BCAAs). The BCAA leucine (L), isoleucine (IL), and valine (V) could be effective additives because they are nonpolar and hydrophobic, which can promote plant uptake of these compounds. Although the effect of exogenously applied BCAA on plant growth is not well known, BCAAs have been reported to increase protein synthesis in humans, and that rate of increase is related to the intake ratio of L to IL and V. The objective of this study was to evaluate the use of L, IL, and V as a nitrogen sources on creeping bentgrass (Agrostis stolonifera) and to investigate the effect of BCAAs on plant growth when all three are applied as a combination. Using specially made rooting tubes, L, IL, and V were applied in a complete factorial and compared with equal urea nitrogen at four rates, as well as an untreated control. Where all three BCAAs were applied in combination, the application ratios of 2:1:1 and 4:1:1 (L:IL:V) were tested. At 63 days after seeding, there were no differences in root length, root weight, or shoot weight; however, BCAA 2:1:1 and 4:1:1 increased creeping bentgrass shoot density by 24% and 32%, respectively, compared with equal urea nitrogen. Where shoot density was increased, nitrogen application rate had no effect. On the basis of these results, BCAAs applied in a complete combination using ratios of 2:1:1 or 4:1:1 (3.03 lb/acre N) will provide a greater creeping bentgrass shoot density compared with equal urea nitrogen.

Restricted access

Mingyuan Xu, Yingwei Wang, Qianbo Wang, Shenglei Guo, Yang Liu, Jia Liu, Zhonghua Tang and Zhenyue Wang

In this investigation, changes in growth and photosynthetic parameters were used to explain the effects of drought stress on morphology and photosynthesis of Eleutherococcus senticosus. Liquid chromatography (LC)-mass spectroscopy (MS) was used to determine the content of eleutheroside B, eleutheroside E, isofraxidin, hyperoside, rutin, and kaempferol under different drought stress conditions to explain the effects of drought stress on secondary metabolism of Eleuthero. Growth and photosynthetic physiological parameters showed that drought stress could inhibit the growth and photosynthesis of Eleuthero. The compounds studied showed the same cumulative trend in various organs of Eleuthero under different drought stress conditions, with the highest content in the moderate drought stress group and the lowest in the severe drought stress group. Among them, the content of eleutheroside B was found to be higher in the 5-year-old stem. The content of eleutheroside E was higher in the 3-year root. The content of isofraxidin was highest in the 5-year-old root. The content of hyperoside, rutin, and kaempferol were higher in the 3-year-old leaves. The results show that a wet soil environment was beneficial to growth and photosynthesis of Eleutherococcus senticosus, and moderate drought stress is conducive to the accumulation of its active ingredients.