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Organic vegetable growers are interested in using the “soil block” method for transplant production as an alternative to plastic flats. The soil block method compresses growing media into a freestanding block in contrast to the cells of a plastic flat. Anecdotal evidence of soil block–grown transplants with increased vigor and root development exists, but limited research has been conducted to evaluate these claims. Furthermore, identifying commercial growing medium for certified organic transplant production is needed. The objective of this study was to compare growth parameters and root development of cucumber (Cucumis sativus) and pepper (Capsicum annum) transplants grown in soil blocks and plastic flats, in combination with four commercially available certified organic media (Beautiful Land Products “Soil Blocking Mix,” Purple Cow Organics “Seed Starter Mix,” Cowsmo “Green Potting Soil,” and Vermont Compost Company “Fort Vee”). A volume-based 50% peat, 25% compost, 12.5% perlite, and 12.5% vermiculite growing medium was also evaluated. A split-plot randomized complete block design with four replications was used with growing method as the whole plot factor and medium as the subplot factor. ‘Marketmore 76’ cucumbers and ‘Yankee Bell’ peppers were seeded in 50-cell flats and soil blocks made with Johnny’s Selected Seeds Stand-up 12 Soil Blocker. Data were collected on growth parameters by destructively sampling cucumbers 3 weeks after seeding, and peppers 5, 6, and 7 weeks after seeding. Root development was evaluated using WinRHIZOTM at the last sampling. Cucumber and pepper transplants performed differently in soil blocks and flats. Cucumbers grown in flats had a significantly greater dry weight than those grown in soil blocks, by 20% in 2022 and by 38% in 2023. In contrast, pepper transplants grown with the soil block method had between 50% and 130% greater dry weight in the final sampling in 2022. Cucumber and pepper transplants grown with Cowsmo “Green Potting Soil” performed poorly, with an up to 144% lower dry weight and up to 167% lower root surface area than transplants grown with the other media. Root development correlated with shoot development, without a specific advantage in soil blocks, although differences in root system architecture should be investigated. The evaluated Beautiful Land Products, Purple Cow Organics, and Vermont Compost Company media can all be considered suitable for growing certified organic vegetable transplants in both soil blocks and flats. Further research is warranted to better optimize the soil block technique, investigate optimum soil block bulk density, and inform growers of appropriate commercially available certified organic growing media for organic vegetable transplant production.

Open Access

Hand weeding is a common but expensive weed management practice in organic carrot (Daucus carota) production. To improve weed suppression and reduce hand weeding in these systems, we developed and tested different biobased polylactic acid (PLA) mulch and compost combinations for carrot production. Carrot was direct-seeded onto PLA mulches and top-dressed with a layer of compost to facilitate carrot germination and rooting through the semipermeable mulch surface. This PLA mulch reduced total weed emergence by 90% relative to bare soil. Yields were not significantly different among mulch types and bare soil controls, partly because weeds were removed weekly after counting. The PLA mulch reduced plant available soil nitrate by 47% relative to bare soil controls. The results suggest that PLA mulch paired with compost is an effective alternative to hand weeding in carrot production. Future research should seek to address the observed nitrogen immobilization.

Open Access

Paphiopedilum Clair de Lune ‘Edgard Van Belle’, an excellent Maudiae-type hybrid that has been propagated by artificial division for a long time. We studied its flower bud initiation, development of floral organs, and flowering habits with a view to providing information for flowering control and efficient commercial production. According to our research, the flower bud initiation phase of this cultivar begins in February every year, and 80% of the plants completed sepal primordium differentiation in March, The flower bud differentiation lasts for 6 to 7 months, until flowering in August. Within 1 to 3 months after flower bud differentiation, all tested plants differentiated lateral buds. After 5 to 6 months, the new, aboveground vegetative shoots reached their maximum growth, with an average plant height of 20 cm, five leaves, and a shoot dry weight of more than 3 g. From February to April of the following year, a new cycle of flower development and vegetative growth began. In addition, this cultivar was notably sensitivity to high ambient temperature during the late phase of flower development, with a flower bud drop rate as high as 33.3% under average day/night temperatures of 29.0/26.5 °C.

Open Access

Nonpoint-source phosphorus (P) from agricultural fields is a contaminant of surface waters, and high soil P fertility exacerbates this problem. Many vegetable growers and gardeners have a history of applying more P than is necessary for optimum plant growth. Avoiding unnecessary P applications is an important part of the long-term solution to reducing P loading in water. When soil P levels are very high, management practices that result in more intense P removal are recommended to reduce these levels and the potential for aquatic ecosystem contamination with P. Growers may apply soluble starter fertilizer containing P to encourage rapid transplant establishment; however, the effectiveness of this practice is unknown for soil P levels considered high or very high. Grafting tomatoes (Solanum lycopersicum L.) onto vigorous rootstocks may help the plant remove more P from the soil than nongrafted plants. This study investigated the effects of organic starter P fertilizers applied to three hybrids of nongrafted tomato and the same hybrids grafted onto ‘Estamino’ rootstock in field-grown conditions during three site-years with high preplant P fertility. The yield, fruit P concentration, and amount of P removed from the field were measured to elucidate starter P and grafting impacts on P removal. Starter P was not impactful on all responses. Grafting increased the total yield by 11.6%, fruit P concentration in a genotype-dependent manner (average of 12.6%), and net P removal from the field by 28.4% (6.0 kg P/ha). Net P removal was positively correlated with the total yield (r = 0.821) and fruit P concentration (r = 0.502), suggesting that practices to increase the yield or P concentration independently increase net P removal.

Open Access

Outbreaks of bitter rot disease occurred in Illinois apple (Malus ×domestica) orchards during 2010–20. This study was conducted to assess the incidence of bitter rot in commercial apple orchards in Illinois, identify pathogen species that cause bitter rot, and evaluate the efficacy of fungicides for managing the disease. Orchard surveys conducted during 2019–21 showed that fruits with bitter rot were present in most of the orchards in southern and central Illinois, whereas only a few orchards in the northern part of the state had symptomatic fruits. A total of 270 isolates of the pathogens were collected from symptomatic fruits of 14 cultivars, and pathogen species were identified based on the morphological and molecular characteristics of the isolates. GAPDH gene sequence analyses identified species of the pathogens as Colletotrichum fioriniae, C. siamense, and C. chrysophilum. Laboratory and orchards studies were conducted to evaluate the effectiveness of fungicides for managing bitter rot disease. Laboratory studies showed averages of 10.3, 9.6, and 0.24 mg⋅L−1 for the 50% effective concentrations (EC50) of benzovindiflupyr, captan, and fluxapyroxad + pyraclostrobin fungicides, respectively. Orchard experiments involving ‘Honeycrisp apples’ were conducted in 2019, 2020, and 2021. Benzovindiflupyr, captan, and fluxapyroxad + pyraclostrobin prevented bitter rot development in the treated plots.

Open Access

Bottlebrush (Callistemon vinimalis) is a widely propagated and cultivated ornamental large shrub with large red bottlebrush-like flowers. Traditional clonal propagation using stem cuttings may be replaced with tissue cultured liners. In this study, we established a container-grown field experiment of bottlebrush ‘Little John’ using liners propagated from both rooted stem cuttings and tissue culture. Growth index was recorded by propagation method periodically through the 34-week period, and both fresh and dry weights of roots and shoots recorded at experiment’s end. Final growth index of plants grown from tissue cultured liners were significantly greater than growth index of plants started from rooted stem cuttings. Both fresh and dry root weight means were significantly greater in plants propagated by tissue culture. Further testing of containerized bottlebrush production, through the flowering stage, will better determine whether tissue-cultured liners accelerate production time vs. liners from stem cuttings.

Open Access

In northern temperate zones, peach trees are vulnerable to cold temperature injury in the fall, particularly as climate change prolongs warm weather in the fall and potentially delays the onset of cold acclimation. Four experiments evaluated how cold acclimation of flower buds and shoot phloem, cambium, and xylem is affected by exposure to varying temperatures in the fall. One-year-old peach shoots from trees grown in Maine, USA, were collected from October through November, exposed to 1, 3, or 6 days of low, high, and freezing temperatures, and subjected to stepwise controlled freezing to about −30 °C. Injury was visually quantified as oxidative browning of flower buds and shoot tissues. High temperature exposure, even of a single day, decreased cold tolerance of flower buds and shoot tissues until late November, when high temperatures only minimally decreased cold hardiness. In mid-November, increasing the duration of high temperature exposure from 1 to 3 days decreased cambium and phloem hardiness, but hardiness in flower buds was not further decreased by the longer duration of 3 days. By late November, hardiness in flower buds, cambium, and phloem was less responsive to high temperature, and was increased by prior exposure to 6 days of freezing. After high temperature, xylem lost hardiness to a small degree in mid-October and late November, but in mid-November this occurred in only one experiment. In this study, deacclimation during high temperature in the fall was greater in cambium and phloem than in flower buds and at times greater than in xylem.

Open Access

This research study evaluated the suitability of controlled-release urea (CRU) as an alternate nitrogen (N) fertilizer source to conventional soluble urea (U) for tomato production under a humid, warm climate in coastal plain soils. Tomatoes are typically produced on raised plastic-mulched beds, where U is fertigated through multiple applications. On the other hand, CRU is applied once at planting, incorporated into soil before the raised beds are covered with plastic mulch. N source and management will likely impact tomato yield, N use efficiency (NUE), and apparent recovery of N fertilizer (APR). A 2-year field study was conducted on fall and spring tomato crops in north Florida to determine the crop N requirement and NUE in tomatoes (var. HM 1823) grown in sandy soils under a plastic-mulched bed system. In addition to a no N fertilizer treatment, three urea N sources [one soluble source and two polymer-coated CRU sources with different N release durations of 60 (CRU-60) and 75 (CRU-75) days] were applied at three N rates (140, 168, and 224 kg⋅ha−1). Across all N sources and N rates, fall yields were at least 20% higher than spring seasons. At the 140 kg⋅ha−1 N rate, APR and NUE were improved, especially when U was applied in fall tomato, whereas preplant CRUs improved N efficiency in spring tomato. Based on the lower APR values found in spring production seasons (0% to 16%) when compared with fall (57.1% to 72.6%), it can be concluded that residual soil N was an important source for tomatoes. In addition, the mean whole-plant N accumulation of tomato was 102.5 kg⋅ha−1, further indicating that reducing the N rate closer to crop N demand would greatly improve conventional vegetable production systems on sandy soils in north Florida. In conclusion, polymer-coated CRU and fertigation U applications were able to supply the N requirement of spring and fall tomato at a 38% reduction of the recommended N rate for tomato in Florida (224 kg⋅ha−1). Preliminary results show that adoption of CRU fertilizers can be considered a low-risk alternative N source for tomato production and the ease of applying CRU once during the bed preparation period for tomato may be an additional incentive.

Open Access

Reusing irrigation water has technical, environmental, and financial benefits. However, risks are also associated with the accumulation of agrochemicals, in addition to ions, plant and food safety pathogens, and biofilm organisms. In this project, we measured the concentration of paclobutrazol (a persistent and widely used plant growth regulator) in recirculated water in greenhouses producing ornamental plants in containers. Solutions were collected from catchment tanks at nine commercial greenhouses across seven states in the United States in Spring and Fall 2014. Paclobutrazol was detected in all samples, with differences observed by season, greenhouse operation, paclobutrazol application method, and irrigation method. Across operations, the residual concentration of paclobutrazol was higher in spring for most greenhouses (ranging from 0 to 1100 µg·L−1) compared with the fall (ranging from 0 to 8 µg·L−1). The spray-drench application method resulted in the highest residual concentrations (up to 35 µg·L−1), followed by substrate drench (up to 26 µg·L−1) and foliage spray (concentrations under 3 µg·L−1). Residual concentrations were higher with overhead irrigation (up to 35 µg·L−1) compared with subirrigation systems (up to 15 µg·L−1). Our results indicate that paclobutrazol is likely to be a growth retardant risk in greenhouse operations recirculating water. A clear understanding of the risks associated with recirculated water intends to support the development and implementation of risk management strategies to ensure and promote safe use of recirculated water in greenhouses. Overall, the most effective preventative strategy is to ensure the use of the minimum amount of the a.i. necessary per unit of space and time.

Open Access