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- Author or Editor: J.P. Morales-Payan x
Greenhouse experiments were conducted in the Dominican Republic to determine the effect of methanol and nitrogen (N) on the yield of `Black Seeded Simpson' lettuce. Plants were individually grown in plastic containers filled with loamy soil and treated with combinations of methanol, folcysteine. N rates (70, 105, 140, and 175 kg/ha) were applied at planting, and aqueous solutions of either ethanol or methanol (0%, 5%, 10%, 15%, and 20%) were applied as a foliar spray when the plants had five true leaves. Plants were harvested 50 days after planting. There were no significant effects of ethanol or methanol on lettuce yield. Lettuce yield was significantly influenced by N rates, with yield increasing as N rates were higher.
Field experiments were conducted in Santo Domingo, Dominican Republic, to determine the effect of increasing population densities of purple nutsedge (Cyperus rotundus) on the yield of eggplant (Solanum melongena). Purple nutsedge populations were established by transplanting viable tubers on 1-m-wide soil beds previously fumigated to suppress volunteer weeds. Nutsedge densities were 0, 50, 100, 150, and 200 plants (tubers) per m2. `Jira' eggplants and purple nutsedge were transplanted the same day and were allowed to interfere season-long. Purple nutsedge initial population densities of up to 100 plants per m2 did not significantly affect the fruit yield of `Jira' eggplants. However, nutsedge densities between 100 and 200 plants per m2 had a significant impact on eggplant yield, causing a linear decline in fruit yield as purple nutsedge density increased. Eggplant fruit yield loss was 22.3% at the density of 200 nutsedge plants per m2.
Nursery experiments were conducted in Santo Domingo, Dominican Republic, to determine the effect of increasing population densities of purple nutsedge (Cyperus rotundus) on the growth of papaya (Carica papaya) transplants. Seeds of `Sunrise Solo', `Red Lady', and `Cartagena Ombligua' were separately sown in plastic 12 × 15-cm containers filled with a 1:1 mixture of sand and loamy soil. Viable purple nutsedge tubers were planted 5 cm apart from the papaya seeds. The purple nutsedge initial population densities were 0, 1, 2, 4, and 6 tubers per container. The crop and the weed were sown the same day and allowed to interfere during 6 weeks. Purple nutsedge density had a significant effect on the height, leaf area, and shoot dry weight of the three papaya cultivars. There was no significant difference in the response of the three papaya cultivars to purple nutsedge densities. In general, as purple nutsedge density increased, papaya growth decreased. Nutsedge interference caused papaya shoot dry weight losses of 15% at the density of one plant per container and 73% at six plants per container.
Container experiments were conducted in the Dominican Republic to determine the effects of nitrogen, gibberellic acid, triadimefon, and kinetin on the seedling growth of sapodilla (Achras sapota) and tamarind (Tamarindus indica). Plants were started from seeds on cylindrical plastic containers (20 × 20 cm) filled with an artificial a 1:1 mixture of sand and loamy soil, allowing the growth of only one plant per container. Nitrogen rates (0.5, 0.75, and 1.0 g N per plant, applied as ammonium sulfate) were factorially combined with the rates (0, 25, 50, 75, and 100 ppm each) of the regulators. When the plants had three true leaves, nitrogen was applied to the growing mixture, whereas the growth regulators were applied foliarly. Plants were allowed to grow during 60 days after treatment. There were no nitrogen and regulator interactions. Kinetin treatments did not significantly influence shoot dry weight and height in either species. Both species responded with linearly increased height, internode length, and dry weight to increasing GA3 concentrations. Increasing rates of the growth retardant triadimefon significantly reduced the internode length and total height of sapodilla and tamarind seedlings. These results suggest that gibberellin and triadimefon could be effectively used as a means to stimulate or retard, respectively, the growth of sapodilla and tamarind.
Greenhouse experiments were conducted in the Dominican Republic to determine the effect nitrogen (N) and the biostimulant folcysteine on the yield of `Black Seeded Simpson' lettuce. Plants were individually grown in plastic containers filled with loamy soil and treated with combinations of N and folcysteine. N rates (35, 70, 105, 140, 175, and 210 kg/ha) were applied at planting, while folcysteine (0, 100, 200, 300, and 400 ppm) was applied as a foliar spray when the plants had five true leaves. Plants were harvested 50 days after planting. The results show that there was an interaction of the effects of N and folcysteine on lettuce yield. The highest yields were obtained with combinations of 300–400 ppm of folcysteine and 140–210 kg N.
Field trials were conducted in Gainesville, Fla., to determine the influence of nitrogen fertilization on the interference effect of purple or yellow nutsedge on the yield of fresh tomato. Nitrogen (N) rates of 50, 100, 150, 200, 250, 300, and 350 kg·ha–1 were applied broadcast to the soil. Before transplanting, 1-m-wide soil beds were covered with plastic and fumigated with methyl bromide to suppress the growth on undesired weeds. Nutsedge-free and purple or yellow nutsedge-infested tomato plots were separately established. `Solar Set' tomatoes were transplanted in the middle of the soil beds, 50 cm apart in a single row. In nutsedge-infested plots, weed densities known to cause significant yield reduction in tomato (100 purple nutsedge plants/m2 and 50 yellow nutsedge plants/m2) were uniformly established perforating the plastic and transplanting viable tubers in the perforations. Purple and yellow nutsedge tubers were transplanted the same day as tomatoes and were allowed to interfere during the whole crop season. Results indicate that N rates had a significant effect on tomato fruit yield in both nutsedge-free and nutsedge-infested treatments. The presence of either purple or yellow nutsedge significantly reduced the fruit yield of tomato at all N rates. As N rates increased, tomato fruit yield reduction caused by the interference of either nutsedge species also increased. When yellow nutsedge was allowed to interfere with tomato, fruit yield loss was as low as 18% at 50 kg N/ha and as high as 42% at 350 kg N/ha. In purple nutsedge-infested tomato, fruit yield reductions ranged from 10% at 50 kg N/ha to 27% at 350 kg N/ha. N effects on nutsedge-free and nutsedge-infested tomato yields were described by quadratic equations, with maximum tomato fruit yield values being reached between 200 and 250 kg N/ha in both nutsedge-free and nutsedge-infested treatments.