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Abstract
Six fertilizers providing N in different forms were incorporated preplant at rates of 400, 800, and 1200 mg N/liter of pot volume for production of Ficus benjamina (L.) plants. Inorganic N status of the media was determined biweekly, and total plant dry weight and N content were determined at the conclusion of the study. Length of time until inorganic N levels in the media dropped below a selected 0.12% level ranged from 94 days for the nitrate-N source to greater than 182 days for the resin coated-N fertilizer. Increases in the rate of N applied of 100%, from 400 to 800 mg N/liter, and of 50%, from 800 to 1200 mg N liter, resulted in increases of 47% and 25%, respectively, in the length of time media N levels remained above the critical level. All N sources produced plants of similar dry weight, whereas only the nitrate-N material gave a lower plant N content than the other fertilizers. Increasing N rate increased plant N content but decreased plant dry weight.
Abstract
Slow-release methylene urea, sulfur-coated urea, and ammonium sulfate fertilizers were applied at different rates and times on muskmelon (Cucumis melo var. reticulatus Naud.) and peppers (Capsicum annuum L.). Increasing N application rate did not affect muskmelon yields, but, in some instances increasing rates up to 134 kg N·ha−1 improved pepper fruit yield and weight. With an increasing N rate, pepper petiole N increased. Timing of fertilizer application did not affect yield of either crop, but application at thinning increased muskmelon fruit weight over preplant application in one instance, whereas the opposite effect occurred in peppers. Split applications and application at thinning increased pepper petiole N content over preplant application in most instances. Early N availability seemed necessary to benefit fruit size and yield, whereas delayed split applications increased only plant N content. Fertilizer source had no effect on either crop in this study. Chemical names used: S-(O-O-diisopropyl phosphorodithionate ester of N-(a-mercaptoethyl)benzene-sulfonamide (bensulide) and N-N-diethyl-2-(1-naphthalenyloxy)propionamide (napropamide).
Abstract
Cabbage (Brassica oleracea L. Group capitata) and onions (Allium cepa L.) were grown using methylene urea, sulfur-coated urea, and soluble N fertilizers applied at different rates and timings. Yield of cabbage increased with increasing N application up to 252 kg N·ha−1, and onion yields increased with N applied up to 134 kg N·ha−1. Nitrogen application also increased fruit weight and leaf N content in some instances. Slow-release fertilizers increased yield, fruit weight, and leaf N of both crops in some instances over soluble N materials. Preplant fertilizer application seemed advantageous on cabbage, whereas split fertilizer application was better with onions. Bended application increased onion yield compared to yields obtained with broadcast application in one experiment. Weather conditions seemed to influence responses to fertilizer type and timing of application, since preplant applications were superior in cool, dry years while the advantages of slow-release materials were evident in wet years. Chemical names used: S-(O-O-diisopropyl phosphorodithionate ester of N-(a-mereaptoethyl) benzene-sulfonamide (bensulide).
Melon growers in the Lower Rio Grande Valley of Texas have observed in the past that particular sizes of melons and the earliness of melons had a direct effect upon economic returns. A replicated study was carried out during two seasons to determine what specific effects plant density, row arrangement, and cultivar would have on fruit size and yield. The study combined six spacing treatments with three cultivars in a randomized design utilizing five replications on top of raised beds on 80-inch centers. Work was initiated by direct seeding and then thinning to the desired spacing interval in plots located in a commercial field. Plots were harvested by commercial harvesting crews. Results indicate that different plant spacings and honeydew cultivars can result in differences in fruit size, earliness, and returns/acre over different seasons and environments although spacing and cultivar acted independent of one another. Lower plant populations resulted in the production of larger fruit and higher plant populations resulted in the production of smaller fruit. Cultivar did affect the size of fruit produced, with some cultivars resulting in larger melons and others producing more small melons. In both seasons, the double-row 24-inch spacing resulted in an earlier harvest and exhibited a higher percent harvest for the first harvest in both years. Cultivar Sure 7050 was significantly later than either `Honeybrew' or `Morning Ice'. Returns/acre were significantly different between spacing treatments for a majority of harvests. The double-row 24-inch spacing resulted in the highest returns/acre. Both `Morning Ice' and `Sure7050' had significantly higher returns when compared to `Honeybrew'.
Bare soil, 13 different polyethylene mulching films, and K-Mulch kenaf paper film were compared to one another for use in early spring production of cantaloupe melons. The mulching treatments were applied to the top of raised beds spaced 200 cm apart in late January and seed of the cantaloupe variety Cruiser were planted in early February. Treatments were replicated five times in a complete randomized block design. Plots were irrigated throughout the season utilizing a drip irrigation system. Crop responses to mulches throughout the growing season were determined by measuring vine growth, fruit yield, Fruit quality and earliness. Mulch tensile strength was determined throughout the season, and ease of cleanup and disposal were evaluated after the growing season. Differences were recorded for treatments particularly regarding ease of cleanup.
The squash leaf curl virus (SLCV), transmitted by the sweet potato whitefly (Bemesia tabaci biotype B), is widespread on fall-planted watermelon in the Rio Grande Valley and Coastal Bend areas of south Texas. The objective of the study was to evaluate colored mulches for their effects on whitefly populations, virus incidence, and watermelon yield. Eleven polyethylene films were included as treatments in both a spring and fall study and were replicated five times in a randomized block design. Plastic mulches caused substantial improvement in melon yields (40%) in the spring crop, similar to responses obtained in other studies on cantaloupes. Fall yield increases due to the use of mulches did not occur. Whitefly populations were much lower in 1996 than they have been in previous years, therefore this was not an adequate test of its effects on whitefly behavior. Even so, there were indications in the fall crop that the use of plastic mulch tended to result in lower whitefly numbers. No evidence was found of any difference between the various mulch materials regarding whitefly counts.
Fertilization programs used commercially for bell peppers (Capsicum annuum) in the subtropical Lower Rio Grande Valley of Texas may vary substantially from recommendations based on research. Therefore, a commercial fertilization program used on a significant fraction of the pepper production in this area was evaluated at two locations. Preplant soil tests showed NO3-N levels were low at one location and very high at the other. Nitrogen application where preplant soil NO3-N was low resulted in a six-fold yield increase (from 197 to 1203 kg·ha–1), and improvements in fruit weight, fruit volume, fruit density, wall thickness, wall strength, and carotenoid and chlorophyll a and b contents. No other nutrient application at either location or N application at the site where preplant soil NO3-N levels were high significantly affected yield by size class, fruit quality characteristics, storage properties, or mineral and organic components. Nitrogen application had the greatest effect on dry-weight accumulation and N uptake during fruit set and maturation when N demand was high. Where N responses were observed, N application increased total dry weight in plant and fruit by 150% and total N uptake by 186%, yet this increase amounted to a N fertilizer uptake efficiency of only 12%. Thus, N should be used judiciously to prevent pollution of drainage and ground waters.