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Dawn M. Alleman and Thomas C. Weiler

Four experiments were conducted over 2 years focusing on water and fertilizer delivery methods with emphasis on minimal resource use. Poinsettia `Freedom', `Celebrate 2'. `Peppermint Pink', `Angelika White', `Lilo' and `Angelika Marble' and geranium `Kim', `Aurora', Ritz', and `Melody' cuttings were grown in 6 inch pots with peat-lite mix and were harvested at marketable size. Nitrogen efficiency was compared by replicating each irrigation treatment with soluble fertilizer (SF) and controlled release fertilizer (CRF). Crops grown with SF were started at 225ppm N for several weeks, then finished at 125ppm N after monitored EC had dropped below 1000μS. CRF treatments were potted up with 1.6 total grams of N available to the plant and irrigated throughout production with tap water. Irrigation treatments included: drip tube leaching, drip tube, ebb & flow, trough. trough lined with capillary mat, trough lined with plastic-covered capillary mat, flats of capillary mat, flats with plastic-covered capillary mat. Daily irrigation volumes were recorded. Weekly data collection included EC, pH, nitrate nitrogen. and ammonium nitrogen. Harvest data included plant dry weight, and total nutrient analyses of plants and substrate. Water efficiency was significantly improved in recirculating systems and with capillary mat systems. No significance was noticed in dry weight or final nutrient analyses across treatments. Significance existed in water quality throughout crop production.

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Theodore J.K. Radovich, Archana Pant, Ian Gurr, Ngyuen V. Hue, Jari Sugano, Brent Sipes, Norman Arancon, Clyde Tamaru, Bradley K. Fox, Kent D. Kobayashi, and Robert Paull

Reducing grower reliance on off-island inputs to promote plant nutrition was identified by industry as a high priority in efforts to improve agricultural sustainability in Hawai’i. A variety of knowledge gaps exist that prevent producers from using locally produced amendments in the fertility program. This study will focus on recent transdisciplinary efforts at the University of Hawai’i to improve understanding of factors that affect variability in the quality, application, efficacy, and cost-effectiveness of locally produced composts, vermicomposts, rendered animal products, and algae in Hawai’i. A series of greenhouse, experiment station, and on-farm trials have supported several conclusions, including 1) aqueous extracts of vermicomposts and high-quality, farmer-produced thermophilic composts can effectively improve crop growth and reduce costs associated with the use of these inputs; 2) replacement of peat and other imports with local materials in vegetable seedling production have the potential to improve seedling vigor and reduce costs in the long term; 3) commercially produced rendered meat products, alone and in combination with commercial composts, are a valuable local source of nitrogen (N); and 4) invasive algae from coral reef remediation may provide a significant source of potassium (K) in the near term, but K content of algae is highly dependent on species and location of growth.

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Mary Jane Clark and Youbin Zheng

The objectives of the current study were to 1) determine the best topdressed controlled-release fertilizer (CRF) application rates for quality and growth of two nursery crops under temperate climate outdoor nursery production conditions in the Niagara region, Ontario, Canada, and 2) evaluate the nutrient status of the growing substrate following topdressing of two CRF types during the growing season. Fall-transplanted Goldmound spirea (Spiraea ×bumalda ‘Goldmound’) and Wine & Roses® weigela [Weigela florida (Bunge) A. DC. ‘Alexandra’] were grown in 2-gal (7.56 L) containers and topdressed on 7 May 2015 with Osmocote Plus 15N–3.9P–9.9K, 5–6 month CRF or Plantacote 14N–3.9P–12.5K, 6 month Homogeneous NPK with Micros. CRF was applied at rates of 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 g nitrogen (N)/pot for both species. The best plants at the end of the growing season (i.e., 23 Sept. 2015) were spirea at 3.0–4.5 and 3.0–6.0 g N/pot, and weigela at 3.0–4.5 and 6.0 g N/pot, with Osmocote and Plantacote, respectively. At CRF rates above these rates, the majority of plants showed no increase in growth or quality attributes. All weigela plants, despite CRF application rate, showed K deficiency symptoms during the study. Using marketable-size criteria and plant growth data over time, estimates of production timing are presented for fall-transplanted, spring-topdressed weigela and spirea. These estimates may assist growers in choosing CRF application rates to meet time-sensitive production goals. Early in the growing season, NO3-N and P concentrations in the growing substrate were highest at CRF rates ≥4.5 and ≥6.0 g N/pot, respectively, and P continued to be high in August and September at 9.0 g N/pot. NH3-N and K concentrations at all CRF application rates were greater early in the growing season and decreased over time. At high CRF rates toward the end of the growing season, concentrations of NO3-N, NH3-N, and P once again increased. Considering crop-specific CRF application rates and understanding changes in growing substrate nutrient status during the growing season may help nursery growers prevent negative environmental impacts from over-fertilizing.

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Sylvia Letícia Oliveira Silva, Renato de Mello Prado, Gilmara Pereira da Silva, Gabriel Barbosa da Silva Júnior, Monica Lanzoni Rossi, and Leónides Castellanos González

This study aimed to evaluate the effects of boron (B) omission on cowpea nutrition and to compare the impact of foliar B fertilization with and without sorbitol on cowpea growth, nutritional status, and B uptake. Two trials using a completely randomized experimental design were conducted. During the first experiment, nutrient solution was provided without B (−B) and with B (+B) in 10 replicates. During the second experiment, a 5 × 2 factorial treatment scheme was used. Five B concentrations (0, 1.25, 2.5, 3.75, and 5.0 g·L−1) were administered foliarly in the form of boric acid with or without sorbitol (500 mmol·L−1) in four replicates. B omission symptoms, root growth, plant organ dry mass and B content, and grain yield were evaluated. B omission induced greater losses in reproductive organ and root growth than in leaf and stem production. It also caused deformation of the middle lamella and accumulation of starch in the chloroplasts. Foliar applications of 2.6 to 2.9 g·L−1 B improved cowpea production. The addition of sorbitol did not enhance plant growth. However, it increased B absorption in the vegetative parts of the plant but did not enhance seed production.

Open access

Abigail Attavar, Lydia Tymon, Penelope Perkins-Veazie, and Carol A. Miles

Grafting is used in watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] production as a means to combat soilborne diseases. To support the development of new rootstock cultivars in the United States, we screened cucurbit germplasm accessions for resistance to verticillium wilt (caused by Verticillium dahliae Kleb.) and for compatibility as watermelon rootstocks. Screening was done using a field naturally infested with V. dahliae [5 and 7.5 colony-forming units (cfu)·g−1 soil in 2017 and 2018, respectively], and plants were inoculated at transplanting (1.5 and 104 cfu of V. dahliae per plant in 2017 and 2018, respectively). In 2017, 56 germplasm accessions from three genera commonly used as rootstocks, Cucurbita, Lagenaria, and Benincasa, were sourced from the U.S. Department of Agriculture (USDA) National Plant Germplasm System and area under the verticillium wilt (disease) progress curve (AUDPC) values ranged from 16 to 397. The 14 accessions with the lowest AUDPC values and good germination (>40%) were used as rootstocks along with the commercial rootstock cv. Tetsukabuto (control), and all were grafted with watermelon cv. Secretariat as the scion in 2018. Grafted plant survival rate was greatest for ‘Tetsukabuto’ (90%) and the accession PI 381840 (L. siceraria) (89%), and ranged from 22% to 85% for all other accessions. All grafted treatments that produced mature fruit in 2018 tended to flower at the same time as nongrafted ‘Secretariat’, with first male and female flowers occurring in 45 to 50 days and 44 to 51 days after transplanting, respectively. There were no significant differences in AUDPC values due to grafting or when accessions were compared with ‘Tetsukabuto’. Only six accessions produced mature fruit when grafted with ‘Secretariat’, indicating they were compatible for watermelon grafting. Fruit weight and number as well as total soluble solids, pH, lycopene content, rind firmness and thickness, and dry matter content were similar for all accessions and ‘Tetsukabuto’ grafted on ‘Secretariat’. Only fruit flesh firmness differed and was highest for ‘Secretariat’ grafted on ‘PI 491316’ and lowest for ‘Secretariat’ grafted on ‘PI 49174’. The six verticillium wilt-tolerant accessions that were compatible with watermelon could potentially be used as rootstocks or as sources of genetic resistance in rootstock breeding programs.

Free access

Shuresh Ghimire, Annette L. Wszelaki, Jenny C. Moore, Debra Ann Inglis, and Carol Miles

The use of plastic biodegradable mulch (BDM) in many vegetable crops such as tomato (Solanum lycopersicum L.), broccoli (Brassica oleracea L. var. italica), and pepper (Capsicum annuum L.) has been proven to be of equal benefit as polyethylene (PE) mulch. However, there are limited research findings on the performance of BDM with a large fruited crop such as pumpkin (Cucurbita pepo L.) where the fruit can rest directly on the mulch for an extended period. To investigate whether heavy fruit might cause the mulch to degrade more quickly than expected, thereby, influencing weed control, fruit yield, and fruit quality including mulch adhesion on fruit, we carried out a field experiment in 2015 and 2016 at two locations in the United States with distinctive climates, Mount Vernon, WA and Knoxville, TN. Three plastic mulches marketed as biodegradable (BioAgri, Organix, and Naturecycle), one fully biodegradable paper mulch (WeedGuardPlus), and one experimental plastic BDM consisting of polylactic acid and polyhydroxyalkanoates (Exp. PLA/PHA) were evaluated against PE mulch and bare ground where ‘Cinnamon Girl’ pie pumpkin was the test crop. There was significant weed pressure in the bare ground plots at both locations over both years, indicating viable weed seed banks at the field sites. Even so, weed pressure was minimal across mulch treatments at both locations over both years because the mulches remained sufficiently intact during the growing season. The exceptions were Naturecycle in 2015 at both locations because of the splitting of the mulch and consequently higher percent soil exposure (PSE), and the penetration of all the plastic mulches at Knoxville by nutsedge (Cyperus sp. L.); nutsedge did not penetrate WeedGuardPlus. At Mount Vernon, overall pumpkin yield across both years averaged 18.1 t·ha−1, and pumpkin yield was the greatest with PE, Exp. PLA/PHA, BioAgri, and Naturecycle (19.9–22.8 t·ha−1), intermediate with Organix and WeedGuardPlus (15.3–18.4 t·ha−1), and the lowest for bare ground (8.7 t·ha−1). At Knoxville, overall pumpkin yield across both years averaged 17.7 t·ha−1, and pumpkin yield did not differ because of treatment (15.3–20.4 t·ha−1). The differences in yield between treatments at Mount Vernon were likely because of differences in the soil temperature. At 10 cm depth, the average soil temperature was 1 °C lower for bare ground and WeedGuardPlus as compared with PE mulch and plastic BDMs (20.8 °C). In contrast, soil temperatures were generally higher (25.2 to 28.3 °C) for all treatments at Knoxville and more favorable to crop yield compared with Mount Vernon. Forty-two percent to 59% of pumpkin fruit had mulch adhesion at harvest at Mount Vernon, whereas only 3% to 12% of fruit had mulch adhesion at Knoxville. This difference was because of the location of fruit set—at Mount Vernon, most of the fruit set was on the mulch whereas at Knoxville, vine growth was more extensive and fruit set was mostly in row alleys. Fruit quality differences among treatments were minimal during storage across both locations and years except for total soluble solids (TSS) in 2016, which was lower for bare ground and WeedGuardPlus compared with all the plastic mulches. Taken overall, these results indicate that pie pumpkin grown with BDM has fruit yield and quality comparable to PE mulch; however, adhesion of some BDMs on fruit could affect marketable yield. Furthermore, paper mulch appears to prevent nutsedge penetration.

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Matthew D. Kleinhenz

A total of 21 and 28 standard and experimental varieties of yellow and white se- and sh2-type sweet corn (Zea mays) were planted in 1999 and 2000 in Fremont and Wooster, Ohio, which are separated by 193.1 km (120 miles) and contain different soil types. Data are reported here for a subset of these varieties (eight yellow, two white) showing a consistently high level of use in Ohio and planted in both years. Endosperm types were planted in distinct, parallel experiments separated by a minimum of 79.9 m (262 ft) at each site. A randomized complete block design with four replications per variety (V) per location (L) was used, with measures of 13 production- and market-based variables taken from emergence to 48 hours after harvest. Soluble solids 48 hours after harvest were greater at Wooster than Fremont in the sh2 study. Variety had a significant, independent effect on mean plant and ear height in the se and sh2 study, respectively, although further analysis of year × variety (Y × V) and location × variety (L × V) interactions suggested that V affected additional traits. On average, `Tuxedo' (se) and `HMX6383S' (sh2) had superior com-binations of grower- and consumer-oriented traits. However, varieties with the highest levels of percent emergence and marketable yield tended to have lower levels of soluble solids, regardless of endosperm type. Y × V interactions were primarily due to changes in the magnitude of values for individual varieties in each year, not from changes in their relative ranking. The Y × L × V interaction was significant (P ≤ 0.05) for marketable yield, plant and ear height, and the ratio of ear length to diameter in the se study, but zero variables in the sh2 study. Coefficients of determination (R 2) for selected plant and ear traits were unaffected by location. Overall, R2 values ranged from 0.04 (number of rows of kernels × ear diameter, sh2 study) to 0.83 (shank length × total ear length, sh2 study). These data reinforce that genetics strongly affect key traits in sweet corn and identify two potential top performers. The data also suggest that independent L or L × V effects may be minor relative to V effects, even when locations are separated by moderate distances and contain different soil types. Therefore, including more varieties but fewer sites may be warranted in future variety trials. The data also suggest that 1) ratings of variety performance should be based on objective measures of grower- and market-oriented traits and 2) shank length × total ear length and ear height × plant height relationships may be used to improve the efficiency of future evaluations.

Free access

Marvin Pritts

primocane-fruiting types because fruiting does not happen within a typical growing season ( Jennings, 1988 ). When fruited both in summer and fall, crop quality can be reduced relative to a fall-only crop ( Pritts, 1989 ). Although double-fruiting is

Open access

Kristin E. Gibson, Alexa J. Lamm, Fallys Masambuka-Kanchewa, Paul R. Fisher, and Celina Gómez

guidelines for technology use; disease management; economic costs and benefits/return on investment; effects on crop quality, production time, uniformity, and shrinkage; fertilizer management; irrigation management; labor management; light management; pest

Open access

Kellie J. Walters, Bridget K. Behe, Christopher J. Currey, and Roberto G. Lopez

nutrient solution could improve crop quality, reduce excessive nutrient accumulation, reduce nutrient deficiencies, and conserve water and labor. Fig. 5. The frequency of nutrient solution replacement as reported by respondents of a 2017 U.S. hydroponic