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Puffy Soundy, Daniel J. Cantliffe, George J. Hochmuth and Peter J. Stoffella

Although floatation irrigation has numerous advantages for vegetable transplant production, including improved seedling health, lettuce (Lactuca sativa L.) transplants grown with floatation (ebb and flow) irrigation can have poor root systems. Floatation fertigation of `South Bay' transplants with K at 15, 30, 45, or 60 mg·L-1 K applied every 2 to 4 days, increased fresh and dry root weight at 28 days. Higher K (24 mg·kg-1) in the medium did not affect root weight. Fresh and dry shoot weight, leaf area, relative shoot ratio (RSR), relative growth rate (RGR), leaf weight ratio (LMR), and root weight ratio (RMR) were unaffected by applied K, regardless of the initial K concentration in the medium. Available K in a vermiculite-containing medium may have supplied all the K required. When 60 was compared with 100 mg·L-1 N at various levels of K, the applied K again did not influence dry root weight; however, at 100 mg·L-1 N, root weight was reduced as compared with 60 mg·L-1 N, regardless of the level of applied K. In a field experiment, pretransplant K had no effect on growth. Transplants grown with no added K in a peat + vermiculite mix with at least 24 mg·L-1 water-extractable K produced yields equivalent to transplants supplied with 15, 30, 45, or 60 mg·L-1 K via floatation irrigation.

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Elio Jovicich, Daniel J. Cantliffe, Peter J. Stoffella and Dorota Z. Haman

Frequent fertigation of soilless-grown bell pepper (Capsicum annuum L.) can increase fruit production, but development of fruit disorders may offset the increase in yield of first-quality (blemish-free) fruit in greenhouses with minimal environmental control. Fruit yield and quality were studied as affected by water volumes and nutrient concentration levels, delivered with irrigation events initiated after determined cumulative solar radiation levels, in ‘HA3378’ bell pepper from October to May in north–central Florida. Irrigation events occurred after solar radiation integral levels (SRI; ±SD) 1.7 ± 0.42, 3.7 ± 0.42, 5.7 ± 0.42, 7.7 ± 0.42, and 9.7 ± 0.42 kW·min−1·m−2, which led to mean number of daily irrigation events of 61 ± 31, 26 ± 12, 17 ± 8, 12 ± 5, and 10 ± 4 respectively. In peat mix, perlite, and pine bark media, volume per irrigation event and concentration levels of the nutrient solution were, in the first experiment, 74 mL standard (74-s), and in a second concurrent experiment, 74 mL half-standard (74-½s) or 3) 37 mL standard (37-s). In both studies, combined marketable fruit yields of first quality and second quality (minor cracking patterns and yellow spots) increased linearly with decreasing SRI (increased events per day). First-quality fruit weight with 74-s was unaffected by media and, in a quadratic response to SRI, reached 5.4 kg·m−2 at 5.7 kW·min−1·m−2. First-quality weight with 74-½s and 37-s did not differ. Weight was unaffected by SRI in peat mix and perlite, and a quadratic response was recorded in pine bark, with yields of ≤3.6 kg·m−2. Fruit cracking incidence decreased with increased SRI, and was generally greater in pine bark. Incidence of yellow spots doubled with 74-½s compared with 37-s, and decreased linearly with increased SRI; the disorder was minor with 74-s. Compared with 37-s, 74-½s decreased fruit with blossom-end rot by 14%, increased marketable fruit weight by 10% in media with the lowest water-holding capacity (perlite, pine bark), and increased nutrient use efficiency. With any media used, the SRI set point of 5.7 kW·min−1·m−2 (daily mean of 17 irrigation events) and 74 mL, at standard nutrient concentration levels, appeared to produce greater blemish-free fruit yield than delivering 37 mL/event or half-concentrated 74 mL/event within the range of SRI means of 1.7 to 9.7 kW·min−1·m−2 (61–10 irrigation events/day). Disorder-tolerant pepper cultivars, better temperature control, and August plantings are additional suggestions for irrigation management to increase first-quality fruit yield.

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Gerald B. Odell, Daniel J. Cantliffe, Herbert H. Bryan and Peter J. Stoffella

Primed, pregerminated, or nontreated `FloraDade' tomato (Lycopersicon esculentum Mill.) seeds in combination with several soil amendments were evaluated in three experiments for stand establishment characteristics and fresh-market fruit yields. Total percent emergence, seedling shoot weight, and marketable fruit yield were not consistently improved by GrowSorb, gel-mix, plug-mix covers, or mixtures with seeds as compared with a control (soil cover). However, rate of emergence was generally faster for plots containing primed or pregerminated seeds with soil amendments than for plots with a soil cover. Primed or pregerminated seeds emerged faster, and had higher total percent emergence and heavier seedling shoot weights than nontreated seeds, but there was little difference in response between primed and pregerminated seeds. Plants from the primed or pregerminated plots produced earlier (first harvest) marketable fruit than did plants from nontreated seed plots in one of three experiments. Priming or pregermination of tomato seeds resulted in a more consistently improved stand establishment than soil amendments.

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Iwanka Kozarewa, Daniel J. Cantliffe, Russell T. Nagata and Peter J. Stoffella

Ethylene synthesis and sensitivity, and their relation to germination at supraoptimal temperatures, were investigated in lettuce (Lactuca sativa L.) seeds matured at 30/20 °C [12-h day/night, high temperature matured (HTM)] or 20/10 °C [12-h day/night, low temperature matured (LTM)]. HTM seeds of both thermosensitive `Dark Green Boston' (DGB) and thermotolerant `Everglades' (EVE) had greater germination at a supraoptimal temperature (36 °C), in both light or dark, than LTM seeds of DGB and EVE. HTM seeds of DGB and EVE produced more ethylene during germination than LTM seeds, regardless of imbibition conditions. The ethylene action inhibitor, silver thiosulfate, led to reduced germination in both cultivars. The ethylene precursor, 1-aminocyclopropane-1-carboxylic acid at 10 mm increased germination of both cultivars at supraoptimal temperatures, whereas germination of HTM seeds was greater than that of LTM seeds. No differences in ethylene perception were detected between HTM and LTM germinating seeds using a triple response bioassay. This study demonstrated that at least one method through which seed maturation temperature influences lettuce germination is by affecting ethylene production.

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Carlos A. Parera, Daniel J. Cantliffe, Peter J. Stoffella and Brian T. Scully

Poor emergence and seedling vigor are common characteristics of many sweet corn (Zea mays L.) cultivars with the shrunken-2 (sh2) mutant endosperm. A rapid and reliable predictor of sweet corn seed field emergence would improve the potential for high quality crops. Field emergence of seven sh2 sweet corn cultivars grown at seven environments in Florida were correlated with laboratory vigor tests. Factor analysis was used to separate noncollinear vigor tests for subsequent multiple regression models. The best single predictor test (R 2 = 0.93***) was an index based on leachate conductivity and germination percentage after a complex stress vigor test involving incubation at 15C. Leachate conductivity after 3 h soaking at 25 or 30C (R 2 = 0.9W***), soil cold test (R 2 = 0.9***), alternate temperature stress conductivity test (R 2 = 0.88***), standard germination test at 30C (R 2 = 0.88***), and an index involving incubation at 25C (R 2 = 0.88***) were also good predictors of field emergence. Noncollinear tests including the towel germination test at 25 C and an alternate temperature stress conductivity test resulted in the best two factor predictor (r 2 = 0.89***), and with glutamic acid decarboxylase activity (GADA) was the best three factor predictor (r 2 = 0.93***). The index of conductivity and complex vigor test (ICS) evaluated seed membrane integrity and potential for pathogen infection, respectively, and can be considered as major factors affecting emergence in sh2 sweet corn.

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Gerald B. Odell, Daniel J. Cantliffe, Herbert H. Bryan and Peter J. Stoffella

Primed, pregerminated, or nontreated tomato (Lycopersicon esculentum Mill.) seeds were field-sown with several soil amendments to assess stand establishment at high temperatures. Soil amendments did not consistently improve tomato stand establishment. However, covering seeds with a fine-textured calcined montmorillonite clay (Growsorb) resulted in similar or improved total percent emergence, emergence rate, and seedling shoot dry weight as compared to the soil cover (control) for nontreated, primed, or pregerminated seeds. Plug-mix (a peat-vermiculite medium) or gel-mix [a 1:1 mixture (v/v) of plug-mix and gel, starch-acrylate copolymer, or polyacrylate polymer], covered over or mixed with nontreated, primed, or pregerminated seeds, did not consistently improve total percent emergence over the soil cover. However, soil amendments generally resulted in faster emergence than the soil cover. Pregerminated seeds imbibed for 60 or 72 hours at 25C generally resulted in reduced stands compared to primed or nontreated seeds. Moisturized seeds imbibed for 48 hours at 25C had faster emergence and heavier seedling shoots than nontreated seeds, regardless of soil amendment. However, primed seeds generally resulted in faster emergence and more plants with heavier seedling shoot weights than nontreated or pregerminated seeds sown at high temperatures.

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Elio Jovicich, Daniel J. Cantliffe, Lance S. Osborne and Peter J. Stoffella

Pepper seedlings can be infested with broad mites prior to transplanting. Transplanted seedlings may not present visible mite damage symptoms and few microscopic mites will be undetected by growers. A rapid increase of the mite population can subsequently result in yield losses in greenhouse-grown crops. Control of broad mites based on biological (N. californicus) and conventional (sulfur) methods were evaluated after infested transplants were introduced into a production greenhouse. Seedlings were artificially infested with two broad mites, 3 days before they were transplanted in mid-September in a passively ventilated greenhouse in Florida. Plants had either two predatory mites released once [4 days after transplanting (DAT)], or twice (4 and 22 DAT), or were sprayed with sulfur (four weekly applications starting 13 DAT when first damage symptoms were noticed). Damage on plants was assessed by an injury scale transformed into percentage values, with 100% being total damage on untreated infested plants. Broad mites were absent in all plants 38 DAT but the damage caused to the plants at this time was negatively correlated (r= –0.95) with marketable yield at 90 DAT. Plants produced no marketable yield where broad mites were not controlled. One or two releases of predators led to respective damages of 56% and 45%, and fruit yields of 2.0 and 3.0 kg·m-2. Plants sprayed with sulfur had a damage of 7% after reaching a maximum of 74% at 18 DAT; however, yields were 4.3 kg·m-2, which was similar to the yield obtained in the uninfested control treatment (4.6 kg·m-2). Releases of predators prior to transplanting and/or higher predator release densities may be needed under similar conditions and will be evaluated in a subsequent experiment.

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Mark A. Ritenour, Peter J. Stoffella, Zhenli He, Jan A. Narciso and James J. Salvatore

Previous research showed that mature green tomato fruit dipped 1 to 4 min in a 1% CaCl2 solutions before storage had significantly increased peel calcium content and reduced postharvest decay. The present experiments, conducted over 3-day periods (reps), evaluate treatment effectiveness under commercial packinghouse conditions. Three cartons of 5 × 6 sized mature green `FL 47' tomatoes were collected from the line (control). CaCl2 was then added to the packinghouse 15,142-L dump tank to a concentration of 1% before more fruit were run through the line and three additional cartons collected. The cycle was repeated after bringing the concentration in the dump tank up to 2% CaCl2. After storage for ≤24 days at 20 °C, postharvest decay was significantly reduced in fruit receiving the 2% CaCl2 treatment. Calcium content in the tomato peel tended to increase with each successively higher CaCl2 treatment, but differences were nonsignificant. Laboratory tests showed Rhizopus more affected by 3% CaCl2, while Alternaria was affected by 2% and 3% CaCl2 solutions. Results were recorded as colony diameter, but colony morphology and sporulation were also affected. Inoculation studies of tomatoes dipped in 1% CaCl2 after wounding with Rhizopus or Alternaria showed better decay control when compared to treating before wounding.

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Monica Ozores-Hampton, Thomas A. Bewick, Peter Stoffella, Daniel J. Cantliffe and Thomas A. Obreza

The influence of compost (derived from MSW and biosolids) maturity on seed germination of several weed species was evaluated. A bioassay was developed by extracting 20 g of compost of different maturities with various volumes of water, then measuring germination percentage of ivyleaf morningglory (Ipomoea hederacea) seeds placed on extract-saturated filter paper in a petri dish. A 20 g (dry weight) compost: 50 mL of water generated an extract that produced the widest percentage seed germination variation in response to composts of different maturity. Ivyleaf morningglory, barnyardgrass (Echinochloa crus-galli L.), purslane (Potulaca oleracea L.), and corn (Zea mays L) were selected as plant indicators to determine the compost maturity stage with maximum germination inhibition. Compost 8-week-old decreased percent germination, root growth, and germination index (combines germination rate and root growth), and increased mean days to germination (MDG) of each plant indicator. Immature 8 week-old compost extract effect on MDG and germination percent of 15 weed species was evaluated. Extract from 8-week-old compost inhibited germination in most weed species, except yellow nutsedge (Cyperus esculentus). Compost extracts derided from immature (3-day, 4-, and 8-week-old) compost resulted in delayed and reduced germination percent of important economic weed species.

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Mark A. Ritenour*, Peter J. Stoffella, Zhenli He and Michael S. Burton

Previous research suggests that treatment of sliced or vacuum-infiltrated tomato fruit with calcium chloride (CaCl2) solutions may reduce decay, but no work on dipping whole tomatoes has been reported. In the present experiments, `FL 47' tomato fruit were collected at the mature green or pink stage from a local packinghouse, held at 12.5 or 25.0 °C overnight, and then dipped in solutions with 0.5% to 5% CaCl2 with or without 150 ppm sodium hypochlorite. Fruit were dipped for 1 to 4 minutes at temperatures ranging from 0 to 35 °C. Mature green fruit dipped in solutions with 0.5% and 1.0% CaCl2 at 35 °C had significantly lower rates of decay following storage at 12.5 °C (90% RH) than the control (27% vs. 36% decay, respectively). These fruit were also significantly softer after 2 weeks of storage than control fruit (0.85 mm vs. 0.74 mm deformation, respectively) and appeared to be slightly more ripe. Decay in fruit dipped in 2% CaCl2 was not significantly different from the control, while fruit dipped in 3% to 5% CaCl2 developed significantly more decay than control fruit. The CaCl2 treatments had no significant effect on decay of fruit treated at the pink stage and none of the treatments at 0 °C significantly affected postharvest decay. Dips in 2% to 5% CaCl2 significantly increased tomato peel calcium content after storage. Dipping time had no significant effect on peel calcium content.