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- Author or Editor: S. J. Locascio x
One of the proposed alternative chemicals for methyl bromide is 1,3-D. The most common forms of 1,3-D products are cis- or trans-isomers of 1,3-D with the fungicidal agent, chloropicrin, containing such mixtures as 65% 1,3-D and 35% chloropicrin (C-35). Soil fumigants are commonly applied under a polyethylene film in Florida raised bed vegetable production. Much of the research regarding cropping system effects of alternative fumigants to methyl bromide has focused primarily on plant growth parameters, with little regard to the atmospheric fate of these chemicals. The objective of this research was to determine both the atmospheric emission of 1,3-D under different plastic film treatments and to evaluate effects of application rates of 1,3-D and C-35 on plant pests, growth, and yield of Sunex 9602 summer squash (Cucurbita pepo L.). Results showed that use of a high barrier polyethylene film (or virtually impermeable film - VIF) greatly reduced fumigant emission compared to ground cover with conventional polyethylene films or uncovered soil. Summer squash seedling survival was a severe problem in several of the 1,3-D alone treatments where no fungicidal agent was added, whereas C-35 resulted in excellent disease control at both full and one-half of the recommended application rates for this chemical. Both 1,3-D and C-35 provided good plant stands and higher yields when applied at their recommended application rates. However, all squash yields were lower than typical squash production levels due to late planting and early winter frost kill. Chemical names used: 1,3-dichloropropene (1,3-D); trichloronitropropene (chloropicrin).
Tomato (Lycopersicon esculentum Mill.) was grown to evaluate various chemicals as possible alternatives to methyl bromide as a soil fumigant. Due to pest pressures from weeds, nematodes, and soil fungi, the use of a broad-spectrum fumigant is essential for economical tomato production. Methyl bromide (MBr) is the fumigant of choice for most growers using polyethylene mulch culture. In 1991, MBr was identified to be in a group of chemicals allegedly responsible for depletion of the stratospheric ozone layer. The U.S. Environmental Protection Agency (EPA) has since called for a phaseout of MBr by the year 2001. At several locations in Florida, alternative soil fumigants were evaluated including 98% MBr-2% chloropicrin (Pic) at 450 kg·ha–1, 67% MBr 33% –Pic (392 kg·ha–1), Pic (390 kg·ha–1), 1,3-dichloropropene + 17% Pic (1,3-D+C17) at 327 L·ha–1, and metham sodium (935 L·ha–1). Metham sodium was also applied by drip irrigation as well as enzone (1870 L·ha–1). Dazomet (448 kg·ha–1) was surface applied and incorporated. Pebulate (4.5 kg·ha–1) was incorporated with some treatments. Pic and 1,3-D+C17 treatments provided control of nematodes and soil fungi. With the addition of pebulate, some nutsedge control also was obtained. Tomato fruit yields with 1,3-D+C17 + pebulate and with Pic + pebulate ranged from 86% to 100% of that obtained with MBr treatments. Pest control and crop production were lower with the other treatments than with the above combinations and with MBr. These studies indicate that no one pesticide can provide the broad spectrum control provided by MBr.
Four cultivars of cassava (Manihot esculenta Crantz), grown at 4 locations, were analyzed for root starch distribution. Starch and glucose variation among cultivars and locations indicated that both genetic and environmental factors were involved. Glucose content of all tissues sampled was less than 2%. The correlation between glucose and starch was negative in the parenchymatous and pith tissues for all cultivars except ‘HMC-2’. Location seemed to have little effect on starch concentration, which ranged from 23-33% in the central pith, 19-26% in the peel, and 34-44% in the parenchymatous tissue between the peel and the pith. The portion of the root closest (proximal) to the plant had a higher starch concentration than did the distal portion.
Methyl bromide (MeBr) is an important and effective soil fumigant commonly used to control weeds and soilborne pests. Because MeBr has been implicated as a contributor to the depletion of stratospheric ozone, it is scheduled for phaseout by 2005. This study examined nonchemical and chemical practices as alternatives to MeBr. Off-season flooding followed by a series of soil preplant chemical treatments [MeBr with 33% Pic; 1,3-D mixed with 17% (C-17) and 35% (C-35) Pic combined with Peb; and metam-Na combined with 1,3-D and Peb were evaluated on spring tomato (Lycopersicon esculentum Mill.) and eggplant (Solanum melongena) production in northern Florida. Pest control and tomato and eggplant yields were not significantly different between the flooded and non-flooded control plots. The most effective alternatives to MeBr were 1,3-D and Pic mixtures (C-17 and C-35) combined with Peb. Tomato and eggplant yields for these chemicals were statistically equivalent to that of MeBr. Tomato, but not eggplant, yield and nematode control were poor with metam-Na combined with 1,3-D and Peb in comparison to the other fumigant combinations. Chemical names used: 1,3-dichloropropene (1,3-D); trichloronitromethane [chloropicrin (Pic)]; S-propyl butyl(ethyl)thiocarbamate [pebulate (Peb)]; sodium N-methyldithiocarbamate (metam-sodium (metam-Na)].
Tomato (Lycopersicon esculentum Mill.) was grown with polyethylene mulch at five locations during a total of nine seasons to evaluate the effects of K source and K rate on fruit yield and leaf K concentration with drip and subsurface irrigation. K sources evaluated were KCl, K2SO4, and KNO3, and K rates varied from 0 to 400 kg·ha-1. Preplant soil K concentrations by Mehlich-1 extraction on the sandy soils and loamy sands used in the study varied from 12 mg·kg-1 (very low) to 60 mg·kg-1 (medium). In seven of the eight studies, K source did not significantly influence fruit yield or leaf K concentration. In the other study with subsurface irrigation at Bradenton in Spring 1992, marketable yields were significantly higher with KNO3 than with KCl as the K source. Tomato fruit yield responded to the application of K in all studies. At Gainesville, Quincy, and Live Oak, with drip irrigation on soils testing low to medium in K, maximum yields were produced with 75 to 150 kg·ha-1 K where the K was broadcast preplant. These rates were 25% to 30% higher than those predicted by soil test. At Bradenton and West Palm Beach on soils testing low to very low in K, where all or part of the K was applied in double bands on the bed shoulder with subsurface irrigation, yield responses were obtained to 225 to 300 kg·ha-1 K. These rates exceeded the maximum recommended K rate of 150 kg·ha-1. Tomato leaf tissue K concentrations increased linearly with increased rates of K application, but were not influenced by K source. These data suggest that the recommendation for K on soils testing low in K be increased from 150 to 210 kg·ha-1 and that this increase should suffice for tomatoes grown with either drip or subsurface irrigation.
Bell pepper (Capsicum annuum L.) cultivars were grown in nine Florida environments to evaluate phenotypic stability of marketable fruit yield (t-ha-') and mean fruit size (g/fruit). A stable cultivar excelled for a particular trait when grown in either favorable or unfavorable environments. A stable cultivar for a given trait was defined as one with an individual mean greater than the grand mean (mean of all cultivars) (x > X), a regression coefficient (b1) ≤ 1 (individual genotypic mean regressed against environmental means), nonsignificant deviation mean squares from regression (S2d), coefficient of linear determination (R2) > 0.50, and coefficient of variation (cv) < the pooled cv. `Ssupersweet 860', `Whopper Improved', and `Ranger' were stable for mean marketable fruit weights and fruit size, and `Ssupersweet 860' and `Whopper Improved' were stable for mean fruit size. Bell pepper cultivars were differentiated for phenotypic stability of yield and fruit size or adaptability to diverse environments. Therefore, through stability analyses, bell pepper plant breeders can identify cultivars or select advanced breeding lines that express adaptability for fruit yields or size to diverse environmental conditions or cultural practices.
The Florida horticulture industry (vegetables, ornamentals, citrus, and deciduous fruit), valued at $4.5 billion, has widely adopted microirrigation techniques to use water and fertilizer more efficiently. A broad array of microirrigation systems is available, and benefits of microirrigation go beyond water conservation. The potential for more-efficient agricultural chemical (pesticides and fertilizer) application is especially important in today's environmentally conscious society. Microirrigation is a tool providing growers with the power to better manage costly inputs, minimize environmental impact, and still produce high-quality products at a profit.
Factorial combinations of trickle or overhead irrigation, polyethylene mulch or no mulch, and 100% NH4NO3 or 50% sulfur-coated urea (SCU) and 50% NH4NO3 were evaluated for their effects on yield and N recovery by tomatoes (Lycopersicon esculentum Mill). In treatments using 100% NH4NO3, 15N-depleted NH4NO3 was applied. Neither tomato yield nor N uptake were affected by irrigation method but both were increased by the use of polyethylene mulch. Higher yields were obtained with NH4NO3 than with 50% NH4NO3 and 50% SCU. An average of 65% of the N in the plant and fruit originated from fertilizer N. Nitrogen recovery from plants and soil at the end of the season in treatments using 15N-depleted fertilizer ranged from 52% to 95%. Highest recovery was obtained with mulch plus overhead irrigation. With this system, 53% of the added N was recovered by the plant and 42% remained in the soil. Only 5% of the added N was lost from the system. All of the other treatments resulted in loss of an average of 46% of the added N.