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- Author or Editor: Bielinski M. Santos x
- HortScience x
Among the current methyl bromide alternatives under study, propylene oxide (Propozone) has shown potential to control soilborne diseases, nematodes, and weeds in polyethylene-mulched tomato. However, further research is needed to determine the appropriate application rates to control nutsedge in the crop. Also, the effect of this fumigant on tomato nutrient absorption has not been determined yet. Therefore, field trials were conducted for this purpose in Bradenton, Fla. Tested rates of Propozone were 0, 190, 380, 570, 760, and 950 L·ha–1 and were shank-applied in raised planting beds three weeks before `Florida 47' tomato transplanting. Examined data indicated that there was a rapid decrease in nutsedge density with 570 L·ha–1. For phosphorus (P) and potassium (K) foliar content, there was a linear increase of P concentrations as rate increase, whereas K content increased rapidly after 190 L·ha–1. The highest tomato yields were obtained with 760 and 950 L·ha–1 of Propozone.
Purple nutsedge can easily penetrate polyethylene mulch films. However, there are no reports on possible differences among mulch films. Because of this situation, field trials were conducted in Ruskin and Bradenton, Fla., during 2002 and 2003. In Spring 2002, the treatments were a) no mulch, b) black Pliant High Barrier mulch, and c) green Klerk's Virtually Impermeable Film (VIF). In Spring 2002, the films were a) black Pliant High Barrier, b) black IPM Bromostop, c) metallized Pliant, and d) green Klerk's VIF. The number of nutsedge emerged through the films was determined. No fumigants or herbicides were applied. Results indicated that the Klerk's VIF had the lowest nutsedge densities. No nutsedge control differences were found between the IPM Bromostop and the metallized Pliant films. These differences might be due to the physical properties of the films, including stretching and thickness.
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.
The response of young `Cartagena Ombligua' papaya (Carica papaya) plants to soil-applied copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) was determined. Nursery experiments were conducted in the Dominican Republic, where Cu (0, 0.023, 0.046, 0.069, and 0.092 g), Mn (0, 0.27, 0.54, 0.81, and 1.08 g), Fe (0, 0.49, 0.98, 1.47, and 1.96 g) and Zn (0, 0.2, 0.4, 0.6, and 0.8 g per plant) were individually applied 20 days after transplanting. There were significant responses to the four elements. Maximum growth was obtained with 0.092 g Cu, 0.4 g Zn, 0.54 g Mn, or 0.98 g Fe per plant.
Greenhouse experiments were carried out to determine the tolerance of two radish cultivars to soil-applied B, Mo, and Zn. Sources used were boric acid (0, 54, 108, 216, 324, and 432 ppm), molybdic acid (0, 1.4, 2.8, 5.6, 8.5, and 11.3 ppm), and zinc sulfate (0, 40, 80, 160, 240, and 360 ppm) applied at planting in addition to the control. Plants were grown in plastic containers of 1.5 L, filled with a potting medium composed of 50% vermiculite, 30% sphagnum peat, and 20% perlite. Treatments were arranged within a randomized complete block design with six replications. Fresh weight of commercial roots was not affected by Mo or Zn applications in either cultivar. However, B applications decreased root fresh weight as rate increased. These results suggest that these radish cultivars perform well in a relatively wide range of Mo and Zn application rates, whereas tolerance to B appears to be low.