Plant biostimulants have received increasing attention in recent years because of their positive effects on crop performance and contribution to agro-ecological sustainability. The aim of this study was to determine the influence of betaine and chitin treatments, alone and in combination, on lettuce plants by changes in the morphology and physiology of plants exposed to regulated deficit irrigation (RDI). Plants were subjected to full irrigation (FI; no water deficiency treatment, field capacity >70%) and RDI (field capacity <50%) conditions until the end of each experiment. We recorded plant yield–related traits, net photosynthesis, and water use efficiency (WUE) values weekly for 4 weeks and carried out three individual experiments to assess the efficacy of biostimulant and irrigation treatments. Betaine (0, 50, and 100 mm/plant) was foliar-treated every 2 weeks during Expt. 1, whereas chitin (0, 2, and 4 g/kg) was applied to the soil at the beginning of Expt. 2. We then applied the optimal concentration of each chemical alone or in combination to the plants as Expt. 3. Compared with negative control, the application of 50 mm betaine and 2 g/kg chitin significantly increased leaf area (LA) per plant by 48.5% and 25.6%, respectively. Furthermore, 50 mm betaine and 2 g/kg chitin treatment showed a clearly protective effect in RDI plants, enhancing their total fresh weights by 26.10% and 75.0%, respectively, in comparison with control. Comparing WUEyield and WUEbiomass, chemical-treated plants had higher values than control. Betaine (50 mm) or chitin (2 g/kg) treatments alone significantly elevated LA, fresh shoot weight, total fresh and dry weights, net photosynthesis, and WUE values, and boosted the water stress tolerance of lettuce under RDI compared with controls. However, a combined treatment of 50 mm betaine and 2 g/kg chitin did not increase the levels of all yield traits under RDI compared with individual chemical treatment. Most leaves appeared healthy, green, and had visually less leaf chlorosis when treated with chitin or betaine under RDI compared with untreated plants subjected to RDI. Our study indicates that applying betaine and chitin improves plant performance against water supply limitations and highlights their potential for the sustainable production of lettuce.
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Furn-Wei Lin, Kuan-Hung Lin, Chun-Wei Wu, Yu-Sen Chang, Kuan-Hung Lin and Chun-Wei Wu
Wayne W. Hanna and Brian M. Schwartz
Jeff B. Million and Thomas H. Yeager
Two experiments were conducted to determine if a leaching fraction (LF)-guided irrigation practice with fixed irrigation run times between LF tests (LF_FX) could be improved by making additional adjustments to irrigation run times based on real-time weather information, including rain, using an evapotranspiration-based irrigation scheduling program for container production (LF_ET). The effect of the two irrigation practices on plant growth and water use was tested at three target LF values (10%, 20%, and 40%). For both Viburnum odoratissimum (Expt. 1) and Podocarpus macrophyllus (Expt. 2) grown in 36-cm-diameter containers with spray-stake microirrigation, the change in plant size was unaffected by irrigation treatments. LF_ET reduced water use by 10% compared with LF_FX in Expt. 2 but had no effect (P < 0.05) on water use in Expt. 1. Decreasing the target LF from 40% to 20% reduced water use 28% in both experiments and this effect was similar for both irrigation practices. For the irrigation system and irrigation schedule used in these experiments, we concluded that an LF-guided irrigation schedule with a target LF of 10% resulted in plant growth similar to one with a target LF of 40% and that the addition of a real-time weather adjustment to irrigation run times provided little or no improvement in water conservation compared with a periodic adjustment based solely on LF testing.
Andrea Stuemky and Mark E. Uchanski
Recent interest in off-season greenhouse-grown food crops, in combination with supplemental (top) lighting (SL), has created opportunities for local production of high-value fruit crops such as strawberries (Fragaria ×ananassa). Light-emitting diodes (LEDs) as SL can be tailored to a specific quality of radiation (i.e., wavelengths) to promote increased production and quality of greenhouse-grown crops. The objectives of this study were to evaluate the effects of three LED light bars on off-season controlled environmental agriculture (CEA) production of 2-day neutral strawberry cultivars: Albion and San Andreas. LED effects on overall vegetative biomass (e.g., stolon production, crown number, and leaf area), marketable fruit yield, and fruit quality [e.g., individual fruit weight and soluble solids content (SSC)] were measured during decreasing daylengths from Oct. to Dec. 2017 (Expt. 1) and increasing daylengths of Jan. to Apr. 2018 (Expt. 2). We hypothesized that the addition of SL via three LED treatments would increase measured parameters. Specifically, it was expected that the LED bars [high blue (HB) and low blue (LB)] with greater intensities of blue and red light would produce greater yields and also increase SSC of the berries. The hypotheses were tested by evaluating three LED light top bars [white far-red (WFR; 440–450 nm), HB, and LB], with wavelength peaks of blue (450 nm) and red (665 nm) light, but differing photosynthetic photon flux densities (PPFDs). Results from these experiments showed that individual strawberry fruit size and SSC were increased with the use of HB and LB LEDs during the shortening days of Expt. 1. Increased leaf area and crown number were also affected positively within all LED treatments (WFR, LB, HB) for ‘San Andreas’. Relative to Expt. 1, the lengthening days of Expt. 2 elicited more limited fruit responses, although increased stolon production within all treatments was reported. In addition, differences between cultivars in leaf area and SSC were observed with ‘San Andreas’ growing larger leaves and ‘Albion’ berries having a greater SSC. Individual fruit weight of both cultivars responded similarly, with increased fruit size in LB and HB, specifically within both Expt. 1 and Expt. 2. Our studies indicate that the addition of SL, in the form of LB and HB improved overall strawberry fruit quality and plant growth during shortening daylengths and under greenhouse CEA conditions.
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’.
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.
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.
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.
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.
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.