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J. Pablo Morales-Payan* and William M. Stall

A field experiment was conducted in Live Oak, Fla., to determine the effect of yellow nutsedge (Cyperus esculentus L.) (YN) density and time of emergence on the yield of direct-seeded squash (Cucurbita pepo L.). YN densities (0, 20, 40, 60, and 100 plants/m2) were established from tubers planted at different times onto polyethylene-mulched beds, so that YN would emerge the same day as the crop or 5, 15, or 25 days later than the crop (DLTC). YN was not controlled after its emergence. The extent of squash yield loss was affected by YN density and time of emergence. When YN emerged the same day as the crop, the yield of squash was reduced by ≈7% (20 YN/m2) to 20% (100 YN/m2). When YN emerged 15 DLTC, crop yield loss was ≈13% at the density of 100 YN/m2>. Regardless of density, YN emerging 25 DLTC did not significantly reduce crop yield as compared to weed-free squash. Thus, in soils with high YN densities (≈100 viable tubers/m2) herbicides and/or other means of YN suppression in squash should be effective for at least 25 days after crop emergence to prevent significant yield loss. If squash yield losses <5% were acceptable, YN control may not be necessary when densities <20 YN/m2 emerge at any time during the squash season or when <100 YN/m2 emerge >25 DLTC. However, YN emerging during the first 15 days of the squash season may produce tubers, which could increase the YN population at the beginning of the following crop season.

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J. Pablo Morales-Payan* and William M. Stall

Field experiments were conducted in Citra, Fla., to determine the effect of acetylthioproline (AP, 250 mg·L-1), gibberellic acid (GA3, 50 mg·L-1), triterpenic acid (TTA, 300 mg·L-1), a commercial glycine-rich complex of free amino acids and short-chain peptides (ACP, 1500 mg·L-1), and two commercial cytokinin-rich seaweed extracts (CST and CTR, both at 30 mg·L-1) on the yield of cilantro (Coriandrum sativum). Aqueous solutions of the AP, ACP, GA3, CST, CTR, and TTA were sprayed on the leaves of cilantro at 15 and 30 days after crop emergence (DAE). Fresh and dry cilantro shoot yields were determined after harvest (60 DAE). No toxicity was apparent from the treatments. For any given treatment, fresh and dry shoot yields were positively correlated. TTA did not significantly affect cilantro yield. GA3, AP, and ACP increased fresh cilantro yield by 23%, 19%, and 16%, respectively, as compared to control plants. When CST or CTR were applied, fresh cilantro yield was 12% higher than in control plants.

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J. Pablo Morales-Payan* and William M. Stall

A glycine-rich mixture of amino acids and short-chain peptides (Siapton) (3 g a.i. per L), two citokinin-rich seaweed (Ascophyllum nodosum) extracts (Stimplex and Triggrr) [50 mg·L-1, active ingredient (a.i.)], a mixture of cysteine and folic acid (Ergostim) (300 mg·L-1 a.i.), and a terpenic acid-rich Siberian fir (Abies sibirica) extract (Silk) (50 mg·L-1 a.i.) were sprayed on St. Augustinegrass residential turf at the beginning of the post-winter regrowth in Gainesville, North-Central Florida, to determine their effect on the growth and aesthetics of the lawn. Above- and belowground biomass, leaf color, and density in St. Augustinegrass were enhanced by all the biostimulants, as compared to untreated St. Augustinegrass plots. The best results were obtained, in descending order, with the cytokinin-rich seaweed extracts, the glycine-rich mixture of amino acids and short-chain peptides, the mixture of cysteine and folic acid, and the terpenic acid-rich Siberian fir extract.

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J. Pablo Morales-Payan and William M. Stall

A field study was conducted in the Constanza Valley [1234 m (4048.6 ft) above sea level, loam soil, average temperature 14.7 to 25.0 °C (58.46 to 77.00 °F), photoperiod 11.2 to 12.6 hours] in the Dominican Republic, to compare the head characteristics, damage caused by diamondback moth larvae (Plutella xylostella), yield, and earliness of cabbage (Brassica oleracea Group Capitata) hybrids `Bravo', `Blue Vantage', `Express', `Genesis', `Green Cup', `Head Start', SW 2007, `Hildur' (SW 2008), `Gretania' (SW 2010), `Hampus' (SW 2011), and XPH 847, to the industry standard `Izalco'. `Genesis' had the highest yield among all the hybrids tested, including `Izalco'. The yield of `Izalco' did not significantly differ from the yield of `Blue Vantage', `Green Cup', `Express', XPH 847, SW 2007, and `Bravo'. However, `Bravo' and `Express' were more damaged by diamondback moth larvae. `Head Start', XPH 847, SW 2007, `Gretania', `Hildur', and `Hampus' were either significantly less productive or more susceptible to damage by the diamondback moth larvae than `Izalco'. In terms of yield, earliness, head shape, and losses due to the diamondback moth larvae, `Green Cup', `Blue Vantage' and `Genesis' were comparable or superior to `Izalco'.

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William M. Stall and Thomas A. Bewick

Twelve sweet corn (Zea mays L. var. rugosa Bonaf.) cultivars were tested for response to nicosulfuron at rates of 0, 18, 36, and 72 g a.i./ha. Weight of marketable ears indicated that five cultivars were intolerant to the herbicide. Three of the cultivars that were intolerant contained the shrunken-2 endosperm mutant (sh) and two contained the sugary enhancer endosperm mutant (se). Cultivars that were most tolerant of nicosulfuron contained the sh, gene. Incorporation of terbufos insecticide before planting led to decreased marketable yield when nicosulfuron was applied at 36 g·ha in all cultivars tested. Chlorpyrifos insecticide incorporated before planting did not affect tolerance to nicosulfuron. Neither soil-applied insecticide affected yield when nicosulfuron was not applied. Chemical names used: 2-[[[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfony]-N,N-dimethyl-3-pyridinecarboxamide (nicosulfuron); S-[[(1,1-dimethylethyl)thio]methyl] O,O-diethylphosphorodithioate (terbufos); O,O-diethyl O-(3,5,6-trichloro-2-pyridyl)phosphorothioate (chlorpyrifos).

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J. Pablo Morales-Payan and William M. Stall

Experiments were conducted to assess the effects of rate combinations of nitrogen (N) and a soil-applied biostimulant based on seaweed (Ascophyllum nodosum) extract (SSE) on the growth of papaya seedlings for transplant production. Seedlings were grown in 180-mL Styrofoam containers filled with a sphagnum/vermiculite/perlite growing medium. N (0 to 2 g per plant) and SSE (drench, 0 to 1 mL per plant) were applied at sowing and 15 days after emergence. N and SSE rates affected overall growth as well as time to attain adequate size for transplanting. In general, increasing N rates resulted in increased growth, and adding SSE enhanced N effects. In terms of increasing overall transplant growth and decreasing the time required from emergence to adequate transplanting size, the best results were found at the highest N and SSE rates.

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J. Pablo Morales-Payan and William M. Stall

The effect of density and time of emergence of the weed tropical spiderwort (Commelinabenghalensis) (TS) on cilantro (Coriandrumsativum) yield were determined in a field experiment in Citra, Fla. TS (0, 1, 2, and 4 plants per m2) emerged at 0, 1, 2, 3, or 4 weeks after cilantro emergence (WACE) and allowed to grow with the crop for the remainder of the season. No significant yield loss was detected when TS emerged 4 WACE. Season-long competition with 1, 2, and 4 TS plants per m2 resulted in yield loss of 27%, 44%, and 65%, respectively. Cilantro yield was reduced by <10% when TS emerged 3 WACE or later, regardless of TS density.

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J. Pablo Morales-Payan and William M. Stall

Competition partitioning experiments were conducted to determine the extent of shoot and root interference between sweet basil (Ocimum basilicum) and the weeds smooth amaranth (Amaranthushybridus) and livid amaranth (A.lividus). Sweet basil and amaranths were grown for 45 days in plastic 19-L containers filled with fertilized sandy soil. The plants were grown: 1) individually (one plant per container = no interference); 2) one basil plant and one amaranth plant together in the same container (= full interference); 3) one basil plant and one amaranth plant together in the same container, training the shoots apart to avoid canopy contact (= below ground interference); or 4) basil and amaranth grown in different containers set side by side (= above ground interference). Each basil/amaranth treatment was replicated five times and the experiment was conducted twice. The effects of smooth and livid amaranths on basil yield were the same for a given type of interference (full, above ground, below ground). Full interference from amaranth reduced basil shoot yield by about 35%, as compared to the yield of basil with no interference from amaranth. The effects of above-ground and below-ground interference on basil yield were additive, but interference above ground had a greater impact (about 21% basil yield loss) than below ground interference (about 14% basil yield loss). These results show that smooth and livid amaranths may drastically reduce sweet basil shoot yield, and that amaranth interference with sweet basil occurred to a greater extent above ground than below ground.

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Salvadore J. Locascio and William M. Stall

Studies were conducted to evaluate the effects of plant spacing, row arrangement, and N rate on bell pepper (Capsicum annuum L.) fruit production. Peppers were grown on a recently cleared sandy soil on raised polyethylene mulch beds during 2 years with one and two plant rows on 1.22-m beds and two and three plant rows on 1.83-m beds with two in-row plant spacings and two N rates. Marketable fruit production was similar during the 2 years. Yields per plant were 30% greater with a 0.31- than a 0.23-m in-row plant spacing. Even with the 33.3% larger number of plants per ha with the latter in-row spacing, yields per ha were similar with both in-row spacings. Yields per plant also varied with bed arrangement and were 50% greater with one row/1.22-m bed than with two rows/1.22-m bed or three rows/1.83-m bed. Plant populations were double with the two latter arrangements (53,818 plants/ha) than the former (25,909 plant/ha) arrangement with a 0.31-m in-row spacing. Thus, total yields were significantly greater with row arrangements with higher than lower plant populations. With three rows/1.83-m bed, the marketable fruit yields per plant were 19% lower for plants grown on the inside plant row than from plants grown on the outside plant rows. Leaf tissue N concentrations were higher during the season with 224 than with 135 kg N/ha, but yield was not influenced by N rate.

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J. Pablo Morales-Payan and William M. Stall

Experiments were conducted to determine the effect of the biostimulant amino levulinic acid (5-ALA) on canopy and root competition of transplanted sweet and purple basils with the weed slender amaranth (Amaranthusviridus). Before transplanting, basil plants were sprayed with an aqueous solution of 5-ALA (0 and 15 mg·L-1 a.i.). Basil and amaranth were grown in plastic 19-L containers either: 1) individually (one plant per container = no interference); 2) one basil plant and one amaranth plant together in the same container (= full interference); 3) one basil plant and one amaranth plant together in the same container, training the shoots apart to avoid canopy interference (= below ground interference); or 4) basil and amaranth grown in different containers set side by side (= above ground interference). When 5-ALA was not applied, full-interference from slender amaranth reduced sweet basil shoot yield by 33%, and purple basil shoot yield by 48%. Above ground interference from slender amaranth was about 65% of the total interference effect. Basil plants treated with 5-ALA were less affected by amaranth interference than untreated basil plants, but the magnitude of the 5-ALA effect was greater in sweet basil than in purple basil. 5-ALA increased the yields of weed-free sweet basil and purple basil by about 15% and 10%, respectively.