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Salvadore J. Locascio

Vegetables are grown throughout the U.S. on various soil types and in various climates. Irrigation is essential to supplement rainfall in all areas to minimize plant water stress. In the U.S., irrigated vegetable production accounts for about 1.9 million ha or 7.5% of the irrigated area. California, Florida, Idaho, Washington, Texas, Nebraska, Oregon, Wisconsin, and Arizona account for 80% of the U.S. production of irrigated vegetables. In the U.S., surface and subsurface (seepage) irrigation systems were used initially and are currently used on 45% of all irrigated crops with a water use efficiency of 33%. Sprinkler or overhead irrigation systems were developed in the 1940s and are currently used extensively throughout the vegetable industry. Sprinkler systems are used on 50% of the irrigated crop land and have a water use efficiency of 75%. In the late 1960s, microirrigation (drip or trickle) systems were developed and have slowly replaced many of the sprinkler and some of the seepage systems. Microirrigation is currently used on 5% of irrigated crops. This highly efficient water system (90% to 95%) is widely used on high value vegetables, particularly polyethylene-mulched tomato (Lycopersicon esculentum), pepper (Capsicum annuum), eggplant (Solanum melongena), strawberry (Fragaria ×ananassa), and cucurbits. Some advantages of drip irrigation over sprinkler include reduced water use, ability to apply fertilizer with the irrigation, precise water distribution, reduced foliar diseases, and the ability to electronically schedule irrigation on large areas with relatively smaller pumps. Drip systems also can be used as subsurface drip systems placed at a depth of 60 to 90 cm. These systems are managed to control the water table, similar to that accomplished with subsurface irrigation systems, but with much greater water use efficiency. Future irrigation concerns include continued availability of water for agriculture, management of nutrients to minimize leaching, and continued development of cultural practices that maximize crop production and water use efficiency.

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James M. Dangler and Salvadore J. Locascio

Tomatoes (Lycopersicon esculentum Mill.) were grown on polyethylene-mulched beds of an Arrendondo fine sand during two seasons to evaluate the effects of trickle irrigation-applied N and/or K, percentages of trickle-applied nutrient(s) (50%, 75%, and 100%), and schedules of nutrient application (variable, 2% to 12.5% of total amount weekly, or constant, 8.3% of the total amount weekly) on the occurrence of fruit external and internal blotchy ripening and fruit mineral nutrient concentration. Trickle-applied fertilizer was injected into the irrigation water weekly during the first 12 weeks of each season. External and internal blotchy ripening were less severe with trickle-applied N supplied as N + K or N than with preplant-applied N. Trickle-applied N + K or N resulted in higher fruit concentrations of N, P, K, Ca, and Mg than with all preplant-applied N. Internal fruit quality improved slightly as the trickle-applied percentage of N and/or K increased from 50% to 100%, but significant differences in exterior quality were not obtained. Internal fruit quality was higher early in the season than late in the season during both years, but this response was not associated with fruit elemental concentration. The weekly schedule of nutrient injection had no significant effect on fruit quality or fruit elemental concentration. Highest yields of high-quality fruit were obtained with 50% trickle-applied N + K.

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James M. Dangler and Salvadore J. Locascio

Tomatoes (Lycopersicon esculentum Mill.) were grown on polyethylene-mulched beds of an Arredondo fine sand during two seasons to evaluate the effects of trickle-applied N and/or K, percentages of trickle-applied N and K (50%, 75%, and 100%), and schedules of N and K application on fruit yield, and leaf and shoot N and K concentrations. The daily irrigation requirement, calculated at 47% of the water evaporated from a U.S. Weather Service Class A pan (Epan), was met by the application of 4.6 mm to 7.2 mm water/day. Fertilizer was injected weekly in a variable (2% to 12.5% of the total amount weekly) or constant (8.3% of the total amount weekly) schedule during the first 12 weeks of each season. Trickle-applied nutrients and trickle-applied percentage of nutrients interacted in their effects on early, midseason, and total marketable fruit yields. When N + K and N were trickle-applied, the mean early total marketable fruit yield decreased linearly from 25.3 t·ha-1 to 16.3 t·ha-1 as the trickle-applied percentage of nutrients increased from 50% to 100%; but when K was trickle-applied (100% preplant-applied N), yields were not affected by the trickle-applied percentage (mean 26.3 t·ha-1). The weekly schedule of N and K injection had no effect on fruit yield or other characteristics. Higher leaf N and K concentrations early in the season were obtained when the respective nutrient was 50% to 100% preplant-applied than when the respective nutrient was 75% to 100% trickle-applied; but late in the season, higher concentrations were obtained when the respective nutrient was trickle-applied. Higher yields, however, were associated with higher early season leaf N concentrations rather than with higher late-season leaf N or K concentrations.

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Salvadore J. Locascio and William M. Stall

Studies were conducted to evaluate the effects of plant spacing, row arrangement, and N rate on bell pepper (Capsicum annuum L.) fruit production. Peppers were grown on a recently cleared sandy soil on raised polyethylene mulch beds during 2 years with one and two plant rows on 1.22-m beds and two and three plant rows on 1.83-m beds with two in-row plant spacings and two N rates. Marketable fruit production was similar during the 2 years. Yields per plant were 30% greater with a 0.31- than a 0.23-m in-row plant spacing. Even with the 33.3% larger number of plants per ha with the latter in-row spacing, yields per ha were similar with both in-row spacings. Yields per plant also varied with bed arrangement and were 50% greater with one row/1.22-m bed than with two rows/1.22-m bed or three rows/1.83-m bed. Plant populations were double with the two latter arrangements (53,818 plants/ha) than the former (25,909 plant/ha) arrangement with a 0.31-m in-row spacing. Thus, total yields were significantly greater with row arrangements with higher than lower plant populations. With three rows/1.83-m bed, the marketable fruit yields per plant were 19% lower for plants grown on the inside plant row than from plants grown on the outside plant rows. Leaf tissue N concentrations were higher during the season with 224 than with 135 kg N/ha, but yield was not influenced by N rate.

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Salvadore J. Locascio and Allen G. Smajstrla

Tomatoes (Lycopersicon esculentum Mill.) were grown on an Arredondo fine sandy soil to evaluate the effects of water quantity applied by drip irrigation scheduled by pan evaporation in a 3-year study. Water was applied to polyethylene-mulched tomatoes at 0, 0.25, 0.50, 0.75, and 1.0 times pan evaporation in one application per day. Irrigation was also scheduled with tensiometers to apply water to maintain soil water tension above 10 cb. The response to irrigation varied with rainfall during the three seasons. In an extremely dry season, fruit yields were doubled by irrigation. Total fruit yields were highest with irrigation quantities of 0.75 and 1.0 times pan and significantly lower with 0.25 and 0.50 times pan. In an extremely wet season, fruit yields were not influenced by water quantities from O to 1.0 times pan. In a third season that was wet from the middle to the end of the season, irrigation more than doubled the marketable fruit yield. However, with an increase in water quantity from 0.25 to 0.75 times pan, yield increased only from 65.9 to 74.1 t·ha-1. Water uses during the three seasons with 0.75 pan were 31.8, 31.1, and 29.6 cm, respectively. Fruit yields were similar with the 0.75-pan and 10-cb tensiometer treatments, but water uses with the latter treatment were 15.8, 17.0, and 18.4 cm during the three seasons, respectively. Tomato leaf N concentrations were reduced slightly with each increase in water quantity applied, even though N was applied with drip irrigation. Leaf N concentrations with the 10-cb treatment were generally equal to or higher than the concentrations with 0.75 pan.

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S. M. Olson and Salvadore J. Locascio

Four experiments were conducted to evaluate the influence of transplant age and container size on `Green Duke' broccoli production. Transplant ages (weeks from seeding) were 3, 4, and 5 weeks in Exp. A, 4, 5, and 6 weeks in Exps. B and D and 3, 4, 5, and 6 weeks in Exp. C. Cell sizes were 2.0 cm (width) × 3.2 cm deep (2.0 cm), 2.5 cm × 7.2 cm deep (2.5 cm), and 3.8 cm × 6.4 cm deep (3.8 cm) with each transplant age. With the smallest container size (2.0 cm), yields were significantly lower in 3 of 4 experiments as compared to the 3.8 cm container size. In 2 of 4 experiments, yields were lower with the 2 cm size as compared to the 2.8 cm container size. In Exps. A and B transplant age did not influence yield, but use of the oldest transplants in Exp. C resulted in reduced yields while use of the oldest transplants in Exp. D resulted in the highest yields Generally, head weights followed similar patterns to the yields.

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James P. Gilreath, Carlene A. Chase and Salvadore J. Locascio

Glyphosate at sublethal rates was applied prebloom, at-bloom, or postbloom relative to the first flower cluster to tomato (Lycopersicon esculentum Mill.) to determine the effect on foliar concentrations of N, P, K, Ca, and Mg. Glyphosate rates of 0, 1, 6, 10, 60, and 100 g·ha-1 were used to simulate the effects of spray drift. In three studies, plant vigor declined with increased glyphosate rates and younger plants were more sensitive than older plants. Plant height decreased as glyphosate rate increased, but the response differed with time of evaluation and with stage of development. In Expt. 1, N content decreased with increasing rate of glyphosate, regardless of stage of development, but response varied with time of evaluation with prebloom and at-bloom applications. In Expt. 2, prebloom glyphosate applications reduced N content, but applications at-bloom did not. P declined with prebloom and at-bloom glyphosate applications in Expt. 1, but only with prebloom applications in Expt. 2. In Expt. 3, P concentrations generally declined with glyphosate rates ≤10 g·ha-1, but were unchanged or increased with rates of 60 and 100 g·ha-1. Tissue K, Ca, and Mg concentrations were not consistently affected by glyphosate rate and sample times. Although significant changes in foliar concentrations of N, P, K, Ca, and Mg occurred, leaf mineral analysis was not considered to be a reliable method of quantifying sublethal effects of glyphosate in tomato. Mineral deficiency did not occur in response to glyphosate application. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).

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James P. Gilreath, Carlene A. Chase and Salvadore J. Locascio

Drift from pesticides can kill or damage nontarget organisms. In these studies, the effects of sublethal rates of the herbicide glyphosate applied prebloom, at bloom, and postbloom of the first flower cluster were evaluated in tomato (Lycopersicon esculentum Mill.). As rates increased from 1 to 100 g·ha-1, foliar injury and flower and fruit number per plant varied with the stage of development at the time of exposure and the time of evaluation after treatment. Plants treated with 60 and 100 g·ha-1 glyphosate prebloom and at bloom had developed moderate to severe foliar injury by 14 days after treatment, but phytotoxicity to plants treated postbloom was only mild to moderate. Blooms abscised from plants treated with 60 and 100 g·ha-1 glyphosate for several weeks after application and fruit set was reduced. Greatest yield losses occurred following treatment prebloom (just prior to bloom) and at bloom. Plants treated before emergence of flower buds, and more mature plants exposed when first cluster fruit were sizing, yielded better than did those treated just prior to bloom and at bloom. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).

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James P. Gilreath, Carlene A. Chase and Salvadore J. Locascio

Cucumber (Cucumis sativus L.) growth and yield in response to application of sublethal rates of 2,4-D at several developmental stages were evaluated in field studies during two seasons. In Expt. 1, prebloom applications of 2,4-D amine reduced plant vigor and increased foliar epinasty as rates increased from 0 to 112 g·ha-1. Early and total fruit yields also declined linearly as 2,4-D rates increased; 112 g·ha-1 2,4-D reduced early yield by 25% and total yield by 20%. In Expt. 2, plant vigor declined with increasing rates of 2,4-D applied at all four stages of development from first true leaf to early fruit enlargement; however, response at stage 1 differed with time after application. Epinasty increased with 2,4-D rate when applied at all developmental stages; however the severity of the response varied with time after application for stages 1, 2, and 3, but not for stage 4. Averaged over all developmental stages, vine length, fresh weight, and yield decreased linearly as rates increased. Early and total yields with 112 g·ha-1 were 22% and 19% lower than those of nontreated plants, respectively. Growth inhibition and yield decline, pooled across 2,4-D rates, were greater when exposure occurred at the earlier stages of development. Chemical name used: (2,4-dichlorophenoxy)acetic acid (2,4-D).

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James P. Gilreath, Carlene A. Chase and Salvadore J. Locascio

Sublethal rates of 2,4-D and dicamba were applied to pepper to evaluate the possible effects of single or multiple exposures to drift from these herbicides. Dicamba induced more foliar injury than did 2,4-D and reduced vigor more as herbicide rates increased. Postbloom applications reduced vigor less than did earlier applications. Epinastic response was affected by stage of development at application and time after treatment. Postbloom applications did not affect yield, but dicamba and 2,4-D applied at earlier stages of development resulted in linear reduction of marketable and total yields as rates increased to 112 g·ha-1. Reductions in plant vigor with increased rates were greater and foliar epinasty was more pronounced with two sequential applications of 2,4-D or dicamba than with single applications. Marketable yields were unaffected by single prebloom applications but declined linearly with two applications. Cull and total yields were not affected by the number of applications. With prebloom and bloom applications of 2,4-D, flower abscission increased and fruit set decreased as rate increased. Chemical names used: 3,6-dichloro-2-methoxybenzoic acid (dicamba); 2,4-dichlorophenoxy)acetic acid (2,4-D).