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- Author or Editor: Bielinski M. Santos x
Field studies were conducted in Florida to determine the effect of early shoot pruning on the severity of bacterial spot, and on the growth and yield of different tomato (Solanum lycopersicum) cultivars. Two tomato cultivars, two inoculation regimes of bacterial spot pathogen (Xanthomonas perforans), and three shoot pruning programs were arranged in a split-split plot design. The tomato cultivars were Tygress and Security-28; shoot pruning included none, light, and heavy; and X. perforans treatments consisted of non-inoculated plots and plots inoculated with a suspension of the pathogen. Tomato plant height was not influenced by any of the three factors or their interactions, whereas the disease severity was higher in inoculated plots versus non-inoculated plants. Early extra-large fruit weight was affected by tomato cultivars and the inoculation with the bacterial spot pathogen, but not by pruning programs or the interaction among factors. Tomato plants inoculated with X. perforans reduced their extra-large fruit weight by 31% in comparison with non-inoculated plants. There were no differences on early marketable fruit weight among the combinations of each cultivar and the three pruning programs. All three factors individually influenced the seasonal marketable fruit weight of tomato, with no difference between light-pruned plants and the non-pruned control for seasonal marketable fruit weight, regardless of tomato cultivars. However, heavy pruning did reduce seasonal yields by 10% in comparison with the non-pruned control. These results indicated that light shoot pruning, which is the standard grower practice in Florida, did not improve bacterial spot control or tomato yields of total and extra-large marketable fruit, which might save up to $50/acre in reduced labor costs for Florida tomato growers.
Two field trials were conducted in the Dominican Republic to determine the influence of in-row distances on ‘Granola’ potato (Solanum tuberosum) minituber yield and economic returns. Seedlings generated from in vitro microtubers were transplanted in open-field raised beds at in-row distances of 0.20, 0.25, 0.30, 0.35, and 0.40 m to compare their minituber yield. In-row distances affected potato minituber weight and number per hectare and per plant. Increasing in-row distances from 0.20 to 0.40 m produced a significant decline on minituber weight per hectare (from 12.6 to 8.7 t·ha−1, respectively). Minituber weight per plant increased linearly with in-row distances, improving from 195 g/plant at 0.20 m to 269 g/plant at 0.40 m. Minituber number per hectare declined linearly as in-row distances increased from 0.20 to 0.40 m, with values ranging between 425,000 and 119,000 minitubers/ha. Maximum values for the number of minitubers per plant were found with 0.20 and 0.25 m, with an average of 6.5 minitubers/plant. However, as distances between plants increased to 0.30 m or farther, the average values decreased to 5 minitubers/plant or less. The results demonstrated that the in-row distances of 0.20 and 0.25 m between plants were the most appropriate from the horticultural standpoint. However, the partial budget analysis reflected that the 0.25 m spacing had the highest marginal return rate among the treatments.
Over the years, efficacy of metam potassium (MK) on purple nutsedge (Cyperus rotundus) control has been inconsistent, in many cases because of a lack of knowledge about application techniques. Therefore, field studies were conducted to determine the effect of water delivery volumes and flow rates on purple nutsedge control with MK, and the influence of MK rates and concentrations on purple nutsedge control. Three separate studies were established for 1) water application volumes and flow rates, 2) MK application rates and concentrations, and 3) MK concentration levels. For the water application volumes and flow rate trials, a single MK rate of 60 gal/acre was injected with either 1 or 2 acre-inch/acre (27,154 or 54,308 gal/acre) of water. The water flow rates were 0.30, 0.45, and 0.60 gal/100 ft of row per minute within each water volume. An nontreated control was included. In the application rate and concentrations studies, treatments were a nontreated control, 30 gal/acre applied with 0.5 acre-inch/acre of water (≈3000 ppm), 60 gal/acre applied with either 0.5 or 1 acre-inch/acre of water (≈6000 and 3000 ppm), 120 gal/acre applied with either 1 or 2 acre-inch/acre of water (≈6000 and 3000 ppm), and 240 gal/acre applied with 2 acre-inch/acre of water (≈6000 ppm). In the MK concentration trials, 0, 2000, 3000, 4000, 5000, and 6000 ppm were tested. Results indicated that neither water volumes nor flow rates used for MK application had a significant impact on purple nutsedge control at 10 weeks after treatment (WAT). However, there was a significant effect of the combinations of MK rates and water delivery volumes on purple nutsedge densities at 4 and 15 WAT. Similarly, MK concentrations obtained from a single application rate resulted in improved purple nutsedge control up to 10 WAT, reducing densities to less than 5 plants/ft2 with 6000 ppm of MK.
A 2-year field study was conducted in two locations in the Dominican Republic to determine the influence of various support systems and nitrogen fertilization programs on passion fruit (Passiflora edulis var. flavicarpa) yield and economic returns. Three trellis systems were used: 1) single line, where a single wire was placed along the planting rows at 2 m high; 2) double lines, where two wires were established along the planting rows at 2 and 1 m high, respectively; and 3) crossed lines, with wires at 2 m high, allowing the vines to grow both along and across the planting rows. Nitrogen (N) fertilization rates were 13, 26, and 52 g/plant of N every 20 days. Plants trained with the single- and double-line support systems combined with 52 g/plant of N had higher marketable yield and had the lowest proportion of non-marketable fruit/plant per year. Partial budget analysis indicated that the single-line support system had a marginal return rate of 36% compared to the double-line support system.
Studies were conducted in the Dominican Republic to determine the short-term response of young `Cartagena Ombligua' papaya (Carica papaya) plants to nitrogen (N), phosphorus (P), and potassium (K) fertilization. N, P2O5, K2O were individually applied 20 days after transplanting at rates 0, 6, 12, 18, and 24 g per plant. Plant height, stem diameter, leaf area, and root and shoot dry weight responded to N and K in a quadratic fashion (N:Y= 30.79+ 1.35X-0.07X2; K20:Y = 30.02 +1.6X - 0.06X2). Maximum growth was obtained with 6 and 18 g of N and K2O, respectively. P fertilization did not significantly affect shoot growth, but it stimulated root growth (Y = 2.02 + 0.41X - 0.013X2).
The effect of varying calcium (Ca), magnesium (Mg), boron (B), and molybdenum (Mo) rates on the growth of young `Cartagena Ombligua' papaya (Carica papaya) plants was studied in experiments conducted in the Dominican Republic. Rates of 0, 3, 6, 9, and 12 g Ca; 0, 0.85, 1.7, 2.55, and 3.4 g Mg; 0, 20, 40, 60, and 80 mg B; and 0, 0.05 0.1,0.15 and 0.2 mg Mo per plant were applied to the soil 20 days after transplanting. Ca did not stimulate plant growth, but instead was toxic at rates of 9-12 g per plant. Mg fertilization significantly stimulated root growth (Y = 2.35 + 0.48X, r 2 = 0.95), but not shoot growth. Mo applications decreased plant growth, whereas B enhanced overall plant growth (Y = 10.64 + 70.5X, r 2 = 0.96).
Experiments were conducted in the Dominican Republic to determine the effect of physical and chemical treatments on the germination of the ornamental palms Roystonea hispaniolana Bailey (Royal palm), Acrocomia quisqueyana Bailey (Corozo palm), Sabal umbraculifera Mart (Cana palm), Phoenix canariensis (Canary Islands date palm), Veitchia merrillii (Becc) Bailey (Manila palm), Chrysalidocarpus lutescens Wendl (Areca palm), and Caryota urens (Fishtail palm). Treatments were seed immersion in water or gibberellic acid 3 (GA3) solution for 72 hours, immersion in concentrated nitric acid for 5 minutes, or cracking of the seed coat. Rate and percentage of emergence 90 days after treatment were measured. The best results for Roystonea, Phoenix, Veitchia, Caryota, and Chrysalidocarpus were obtained soaking the seeds in water or a 200-ppm gibberellic acid solution. Nitric acid and seed coat cracking significantly reduced the germination percentage in all the species, except Acrocomia guisqueyana and Sabal umbraculifera. Seeds of Acrocomia did not germinate as a response to any of the treatments tested. Sabal seeds germinated only after coat cracking or nitric acid treatment.
Trials were conducted under controlled conditions to determine the tolerance of young papaya plants (15 cm tall) to postemergence herbicides. Herbicides used were paraquat (1.68 Kg ai/Ha), MSMA (2.24 Kg ai/Ha), 2,4-D (4.26 Kg ai/Ha), bromoxynil (0.28 Kg ai/Ha), cyanazine (1.12 Kg ai/Ha), dimethenamid (1.12 Kg ai/Ha), endothal (0.56 Kg ai/Ha), imazameth (0.067 Kg ai/Ha), imazethapyr (0.028 Kg ai/Ha) lactofen (0.12 Kg ai/Ha), oxyfluorfen (0.03 Kg ai/Ha), acifluorfen (0.28 Kg ai/Ha), atrazine (2.24 Kg ai/Ha), and bentazon (1.12 Kg ai/Ha) as well as the untreated control. Atrazine, bentazon, cyanazine, imazemeth, imazethapyr, and dimethenamid did not cause phytotoxicity at the rates used and were equal to the untreated control. Other herbicides caused severe injuries followed by total death at 10 days after treatment.
Container experiments were conducted in the Dominican Republic to determine the effects of gibberellic acid (GA3) and nitrogen (N) treatments on the seedling growth of Spanish lime (Melicoccus bijugatus), golden apple (Spondias dulcis), and acerola (Malpighia punicifolia). The three species responded with linearly increased height and dry weight to increasing GA3 levels. Each species responded differently to N rates. Spanish lime did not respond to N supply, whereas golden apple was highly responsive and the growth of acerola was reduced at high N rates.
Nursery experiments were conducted in the Dominican Republic to determine the tolerance of tamarind (Tamarindus indica), acerola or Barbados cherry (Malpighia punicifolia), and zapote (Calocarpum sapota) irrigation with saline water (0, 2, 4, 6, and 8 dS/m) at different frequencies (every 24, 48, and 72 hours) during 60 days. Results indicate that tamarind was the less salt-sensitive and zapote the less salt-tolerant of the three species. Linear relationships were found between salt concentration and growth, with biomass accumulation decreasing as salinity and irrigation frequency increased.