Cilantro (Coriandrum sativum L.), also called coriander, is an herbaceous, annual plant that is cultivated worldwide for its leaves and seeds. Cilantro has a strong propensity to bolt quickly in hot weather and under long-day (LD) conditions, which affects the flavor and renders the crop unmarketable. High incidence of preharvest bolting in open-field production can cause significant economic loss. The phytohormone gibberellic acid (GA) regulates stem elongation and floral initiation in many LD rosette plants. In pilot experiments, we found that GA induced bolting in greenhouse-grown cilantro and that plant growth regulators (PGRs) with anti-GA activity can delay this process. We then explored the effects of different GA inhibitors on reducing the incidence of bolting in cilantro grown in a commercial open-field environment. Four field trials were conducted on a commercial farm near Clewiston in Florida between Fall 2016 and Spring 2018. Different growth regulators were applied at different times, ranging from 5 to 8 weeks after seeding (WAS), and plants were harvested 2 to 3 weeks thereafter. Applications of GA inhibitors significantly reduced the incidence of bolting in three of the four trials, but the extent depended on the type of inhibitor used. The results from one trial were inconclusive due to changes in weather that prevented bolting in the entire field. Overall, plots treated with prohexadione calcium and paclobutrazol were most effective and reduced bolting by up to 78%. Applying the PGRs at 5 and 6 WAS was more effective than at 7 or 8 WAS.
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Bo Meyering, Adam Hoeffner and Ute Albrecht
Fan-Hsuan Yang, Lisa W. DeVetter, Bernadine C. Strik and David R. Bryla
Accumulation of calcium (Ca) in fruit is largely caused by transpiration and varies depending on the concentration of Ca in the xylem fluid. The objective of the present study was to evaluate the relationship between fruit stomatal functioning and Ca accumulation during different stages of development in northern highbush blueberry (Vaccinium corymbosum L.). Stomata were scarce on the berries and were concentrated primarily on the distal end near the calyx. The density of the stomata was greatest at petal fall, averaging 5 to 108 stomata/mm2 from the proximal end (pedicel end) to the distal end of the berries. Stomata were wide-open at the early green stage of berry development and had a slight deposit of wax along the guard cells. As the berries expanded during the initial period of rapid growth (stage I), most of the stomata remained near the distal segment of the berries; by the late green stage, almost none was found in the middle and proximal segments. The majority of these stomata were completely covered with wax when the berries began to change color and ripen (stage II and stage III). Stomatal conductance (g S) of the berries averaged 45 mmol·m−2·s−1 at petal fall and rapidly declined as the fruit developed. By the fruit coloring stage, conductance was low and remained less than 15 mmol·m−2·s−1 throughout the ripening period. In four cultivars, including Duke, Bluecrop, Aurora, and Elliott, Ca uptake in the berries increased rapidly during the early green stage; however, it slowed considerably between the late green and fruit coloring stages and stopped completely during fruit ripening. The results of this study strongly suggested that practices used to increase the Ca content of blueberries, such as the application of foliar fertilizers, should be performed early in the season during the first few weeks after flowering.
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.
Jaime Barros da Silva Filho, Paulo Cezar Rezende Fontes, Paulo Roberto Cecon, Jorge F.S. Ferreira, Milton E. McGiffen Jr. and Jonathan F. Montgomery
Potato seed production by conventional methods represents a sizeable investment that, when passed on to farmers, can decrease their profit margins. Potato minitubers produced by aeroponic systems are space- and cost-efficient, and they also provide healthy propagules to be used by farmers. We evaluated the effects of different misting nozzle types, with and without an antidrip feature, and spray direction on potato minituber yield using the Federal University of Viçosa (UFV) Aeroponic System. Potato plants (cv. Agata) propagated from sprouts were grown in a covered, high-density 100-L polyethylene bucket. The experiment was set up in a randomized complete block design with four replicates and eight treatments combining misting nozzle types (Fogger, MA-30, and CoolNet) with and without antidrip and comparing upward with downward spray directions. Plants were evaluated weekly from 33 to 68 days after transplant (DAT). The parameters used to evaluate treatments were number and mass of minitubers as a function of harvest times, dry mass of roots, stems, leaves, and total biomass. The number and fresh weight of minitubers, as well as root dry weight, stems, leaves, and total biomass were affected by misting nozzle types and spray direction. Treatments also affected biomass partitioning of roots, stem biomass, and the shoot:root ratio. There was also an effect of harvest time on the number and fresh weight of minitubers for various combinations of misting nozzle type and spray direction, except for minituber number with the CoolNet misting nozzle without antidrip and downward spray direction. On the basis of the assessed parameters, the best minituber production system was achieved with the Fogger spray combined with no antidrip, a rate of 12 L·h−1, and with the downward spray direction. The UFV Aeroponic System produced an average of 491 minitubers per plant. This system is simple to implement and may lead to a more affordable upscaling of potato seed minituber production.
Crysta N. Harris, Ryan W. Dickson, Paul R. Fisher, Brian E. Jackson and Anissa M. Poleatewich
Pine (Pinus sp.) wood products have potential to immobilize fertilizer nitrogen (N) and influence plant growth when used in soilless substrates for the production of containerized floriculture crops. Peat substrate was amended with (by volume) 30% pine wood fiber (peat:fiber) during a production phase with fertigation and a simulated consumer retail phase with clear-water irrigation using container-grown ‘Supertunia Vista Bubblegum’ petunia (Petunia ×hybrida). The objective was to evaluate substrate effects on substrate and plant tissue nutrient level and plant growth, with an emphasis on evaluating N immobilization from wood product amendments. Substrates consisting of peat amended with hammer-milled pine wood (peat:wood) or coconut (Cocos nucifera) coir (peat:coir) were used for comparison, and a 100% peat substrate (peat) served as a control. In Expt. 1, amending peat with pine wood fiber had no effect on leaf SPAD chlorophyll index, shoot growth, plant height and width, substrate N, or percent shoot tissue N at the end-of-production. In Expt. 2, plants grown in peat:fiber had reduced flower number, plant height and width, and shoot growth compared with plants grown in the 100% peat control. However, petunia grown in peat:fiber substrates maintained dark-green foliage with high leaf SPAD chlorophyll index values (≥44.4) and ≥45 flowers/plant, and therefore were considered marketable plants. During the production phase in both Expts. 1 and 2, N concentrations remained within the target range for petunia in both the shoot tissue and root-zone for all substrates. In addition, there was no statistical evidence of N immobilization for any substrate blend for either of the N drawdown procedures. In both Expts. 1 and 2, root-zone nutrients became depleted during the consumer phase when irrigation was with clear water (no fertilizer), and petunia developed uniform symptoms of leaf chlorosis and N deficiency. Results of this study indicate that peat amended with 30% pine wood fiber, hammer-milled pine wood, and coconut can be used for production of containerized petunia with minimal effects on plant growth or need to adjust the fertilizer program. However, increasing pine wood to >30% of the substrate volume may require growers to increase fertilization and adjust irrigation practices to compensate for greater risk of N immobilization and changes in substrate physical properties.
Roland Ebel, Esmaeil Fallahi, John L. Griffis Jr., Dilip Nandwani, Donielle Nolan, Ross H. Penhallegon and Mary Rogers
Urban horticulture describes economically viable horticultural production activities conducted in a city or suburb. It is a growing segment of horticulture in the United States as well as in developing countries, where the enormous growth of megalopolis is not backed by a simultaneous increase of farmland or agricultural productivity. Today, urban horticulture includes food sovereignty in underprivileged neighborhoods, increased availability of vegetables and fruits in big cities, healthy and diverse diets, improved food safety, low transportation costs, efficient resource use, and the mitigation of environmental impacts of horticultural production such as the emission of greenhouse gases. The workshop “Urban horticulture: From local initiatives to global success stories,” held at the 2018 American Society for Horticultural Science (ASHS) conference in Washington, DC, featured present and historical success stories of urban horticulture from Asia, Africa, Latin America, and the United States.
Benjamin L. Campbell and William Steele
The number of pollinators has been reported to be decreasing for the past several decades. Numerous sources (e.g., climate change, pesticides, loss of habitat) have been noted as potential contributing factors to the decline. With respect to the green industry, the impact of pesticides on pollinator decline and consumer response to this impact is of critical importance. Although no definitive link exists of pesticides being a major contributing factor to pollinator decline, some retailers have banned their suppliers from using certain pesticides. As various sources (e.g., universities, media, activist groups) provide information (both positive, neutral, and negative) about the impact of pesticides on pollinators, no information exists regarding how consumers value such information. Using a sample of Connecticut consumers, this study evaluates how both information source and information type impact a consumer’s decision to purchase pollinator-friendly plants in the future. The study finds that consumers exposed to either neutral (no link between pesticides and pollinator decline) or negative (link between pesticides and pollinator decline) information from universities and major media outlets indicate they will purchase more pollinator-friendly plants compared with the no information (control) treatment. The results show that information from the federal government, nursery/greenhouse industry associations, and environmental activist groups have the same impact on self-reported future pollinator-friendly plant purchasing as the no information group.
Mary Jane Clark and Youbin Zheng
Commercially available Canadian retail potting mixes were evaluated for physical and chemical properties, as well as for plant performance of petunia (Petunia ×hybrida ‘Storm Pink’), tomato (Solanum lycopersicum ‘Better Bush’), and zonal geranium (Pelargonium ×hortorum ‘Savannah Red’) plants grown outdoors at the Vineland Research and Innovation Center in the Niagara Peninsula in Ontario, Canada. Chemical properties, but no physical properties, resulted in significant correlation with plant growth index, overall appearance, and yield (i.e., flower, fruit, or inflorescence number for petunia, tomato, and zonal geranium, respectively). The performance of all species was best when initial potting mix pH and electrical conductivity (EC) values were in the ranges of 5.20 to 6.17 and 2.76 to 4.33 mS·cm−1, respectively. The physical properties of the container capacity, total porosity, air space, and bulk density were acceptable for all plants in this study and ranged from 71% to 80%, 78% to 96%, 8% to 20%, and 0.08 to 0.22 g·cm−3, respectively. The minimum concentrations of the initial nitrate (NO3 −), ammonium (NH4 +), phosphorus (P), and potassium that were acceptable were 104.4, 61.3, 47.9, and 150.5 ppm for petunia and 96.8, 61.3, 51.7, and 143.3 ppm for tomato, respectively. The minimum concentration of NO3 − that was acceptable was 66.1 ppm for zonal geranium. Overall appearance at 4, 8, and 10 weeks after transplanting was correlated with initial potting mix EC, NO3 −, and calcium for all species, with pH, NH4 +, and P for petunia, with P for tomato at all time points, and with P for zonal geranium after 10 weeks. Although it is difficult to discern how each nutrient impacts plant performance, this study indicated that it is essential to have a balanced and adequate supply of nutrients in consumer potting mixes. The ability of a potting mix to maintain an appropriate pH for the duration of the growing season may prevent nutrient deficiency symptoms, especially for pH-sensitive species like petunia. This study is the first to provide a benchmark of currently available retail potting mixes for Canadian consumers.
Isaac T. Mertz, Nick E. Christians and Adam W. Thoms
The branched-chain amino acids (BCAA) leucine (L), isoleucine (IL), and valine (V) are synthesized in plants and are essential to growth in most organisms. These compounds can be absorbed by the plant when foliarly applied, but plant catabolism of BCAA is not completely understood. A recent study observed that BCAA applied in a 2:1:1 or 4:1:1 ratio (L:IL:V) increased creeping bentgrass (Agrostis stolonifera) shoot density compared with applications of equal urea nitrogen (N) at 3.03 lb/acre N. The present study investigated whether those increases could translate to a quicker establishment rate of creeping bentgrass grown from seed in standard greenhouse pots. The BCAA applications were compared with equal N applications using urea and a commercially available amino acid product. All N treatments were applied at 3.03 lb/acre N, per application and applied a total of four times on a 14-day interval starting 14 days after seeding. Measurements included final shoot density counts and root and shoot weights, as well as digital image analysis of percent green cover for each greenhouse pot every 7 days. No differences were observed after 70 days in shoot weight, or percent green cover between BCAA treatments and urea; however, BCAA 2:1:1 and 4:1:1 increased shoot density 21% and 30%, respectively, compared with urea, and were equal to the commercially available amino acid product. Applications of BCAA 4:1:1 also increased creeping bentgrass rooting weight by a factor of 7 compared with urea N.
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’.