Early Marketable Yield Research Articles

Influence of Cultivar, Growing Media, and Cluster Pruning on Greenhouse Tomato Yield and Fruit Quality

Cultivars and growing media are important components of a successful greenhouse tomato (Solanum lycopersicum) operation. Two studies were conducted simultaneously and independently in two 30 × 96-ft greenhouses in Spring 2006 and 2007 (January–July) to assist producers in selecting appropriate cultivars and reducing production cost. The first study was conducted to evaluate yield, fruit weight, fruit quality, and shelf life of ‘Geronimo’, ‘Quest’, and ‘Trust’ tomatoes planted in perlite and pruned to three or four fruit per cluster. The second study was conducted to determine the initial cost of perlite, pine bark, and rockwool growing media and their effect on yield of ‘Quest’ pruned to three or four fruit per cluster. ‘Geronimo’ produced the highest total marketable yield and ‘Trust’ produced the lowest. ‘Trust’ produced more cull yield and lower fruit weight than ‘Geronimo’ or ‘Quest’. Pruning clusters to three fruit increased total marketable yield and fruit weight, and reduced cull yield of all cultivars. Only ‘Geronimo’ produced higher early marketable yield at four fruit per cluster. All cultivars produced higher early marketable yield in 2007 than in 2006. Tested cultivars had similar fruit content of potassium and sodium and similar concentration of soluble solids. ‘Trust’ fruit had a higher pH than the other two cultivars. About 92% of ‘Quest’ tomatoes remained marketable after storage at 67 °F for 1 week. ‘Geronimo’ and ‘Trust’ had only 83% and 78% marketable fruit, respectively, under the same conditions. Initial costs to grow greenhouse tomatoes in perlite were higher than in rockwool, and were the lowest in pine bark. Plants grown in perlite produced higher total marketable yield than plants grown in either of the other media. They produced lower cull yield than plants grown in rockwool, but produced similar cull yield to plants grown in pine bark. Pruning clusters to three fruit increased total marketable yield and fruit weight in both studies. Pruning clusters to four fruit increased cull yield in both studies regardless of planting year.

Soil Solarization as an Alternative to Methyl Bromide Fumigation for Annual Strawberry Production in a Mediterranean Area

ABSTRACT This study compares the effects of soil solarization and methyl bromide fumigation on the growth and yield of strawberry plants (Fragaria xananassa Duch.) cultivated under plastic tunnel conditions. The study was conducted in a Mediterranean coastal area, in four consecutive annual production cycles in a field with no history of methyl bromide fumigation and 2-year history of strawberry production. In all 4 years, solarization was conducted for 7- to 9-week intervals from late June to early September. Cultivar Tudla frigo-plants were planted through mulch in the first week of September of each year. Average daily soil temperatures in solarized plots measured at 15 cm depth were 6.0, 8.1, 7.8, and 8.4 °C higher than the control, during Summer 2001, 2002, 2003 and 2004, respectively. Solarization produced 781, 610, 630, and 525 hours above 37 °C at 15 cm depth during the first, second, third, and fourth year, respectively. In the first year, solarization significantly increased both early and total marketable yields by 15% compared with the fumigated plots, whereas in the successive years, solarization and fumigation were equally effective in increasing yields when compared to untreated plots. No significant differences in average fruit weight were observed between solarized and fumigated plots in individual years. The study demonstrated that the Mediterranean coastal areas have appropriate environmental conditions to apply soil solarization in strawberry planting as a viable substitute to methyl bromide fumigation.

Reconciling pH for Ammonia Biofiltration and Cucumber Yield in a Recirculating Aquaponic System with Perlite Biofilters

Integrating hydroponic and aquaculture systems (aquaponics) requires balanced pH for plants, fish, and nitrifying bacteria. Nitrification prevents accumulation of fish waste ammonia by converting it to NO3 –-N. The difference in optimum pH for hydroponic cucumber (Cucumis sativa) (5.5 to 6.0) and nitrification (7.5 to 9.0) requires reconciliation to improve systems integration and sustainability. The purpose of this investigation was to: 1) determine the ammonia biofiltration rate of a perlite trickling biofilter/root growth medium in an aquaponic system, 2) predict the relative contribution of nitrifiers and plants to ammonia biofiltration, and 3) establish the reconciling pH for ammonia biofiltration and cucumber yield in recirculating aquaponics. The biofiltration rate of total ammonia nitrogen (TAN) removal was 19, 31, and 80 g·m−3·d−1 for aquaponic systems [cucumber, tilapia (Oreochromis niloticus), and nitrifying bacteria (Nitrosomonas sp. + Nitrobacter sp.)] with operating pH at 6.0, 7.0, and 8.0, respectively. With the existing aquaponic design (four plants/20 L perlite biofilter/100 L tank water), the aquaponic biofilter (with plants and nitrifiers) was three times more effective at removing TAN compared with plant uptake alone at pH 6.0. Most probable number of Nitrosomonas sp. bacteria cells sampled from biofilter cores indicated that the aquaculture control (pH 7.0) had a significantly higher (0.01% level) bacteria cell number compared with treatments containing plants in the biofilter (pH 6.0, 7.0, or 8.0). However, the highest TAN removal was with aquaponic production at pH 8.0. Thus, operating pH was more important than nitrifying bacteria population in determining the rate of ammonia biofiltration. Early marketable cucumber fruit yield decreased linearly from 1.5 to 0.7 kg/plant as pH increased from 6.0 to 8.0, but total marketable yield was not different. The reconciling pH for this system was pH 8.0, except during production for early-season cucumber market windows in which pH 7.0 would be recommended.

Differential Watermelon Fruit Size Distribution in Response to Plastic Mulch and Spunbonded Polyester Rowcover

Plasticulture has been successfully used to enhance growth and yield of horticultural crops, and also for season extension in cooler climates. The effect of three plastic mulches (silver on black, photoselective thermal green, and black) in combination with spunbonded polyester rowcover (0.9 oz/yard2) on spring-planted watermelon (Citrullus lanatus) production was investigated. Two red-fleshed cultivars [Sangria (seeded) and Crimson Jewel (triploid)] were used. Plastic mulches increased early and total marketable yield in comparison with bare ground for both cultivars, but net benefit increased in ‘Crimson Jewel’ only. In contrast, yield and net benefit were the same among plastic mulches. Rowcover increased soil and air temperature, with the effect being greatest at lower ambient temperatures. During a near-freeze event, air temperature under the rowcover was about 7.2 °F higher than without a rowcover. Rowcover increased early and total marketable yield, but fruit weight decreased in both cultivars. Yield distribution into three fruit size categories was inconsistent between the cultivars. In ‘Sangria’, the large fruit category had the highest yield proportion for all treatments. In contrast, the highest yield proportion of ‘Crimson Jewel’, with exception of mulch without rowcover, corresponded to small fruit. Rowcover increased gross income at wholesale prices, but net benefit was not different from without rowcover. Protection of high-value plants, such as triploid watermelon, against light freezes, however, may still justify the use of rowcover in early plantings.

Performance of Methyl Bromide Alternatives in Strawberry

Field studies were conducted to compare the performance of several methyl bromide (MBr) alternative programs on sting nematode (Belonolaimus spp.) control and marketable yield of ‘Camarosa’ strawberry (Fragaria ×ananassa). The tested fumigation programs were 1) MBr + chloropicrin (Pic; 67:33 v/v) at 350 lb/acre, 2) Pic + metam sodium (MNa) at 300 lb/acre and 37.5 gal/acre, 3) 1,3-dichloropropene (1,3-D) + Pic at 35 gal/acre, 4) 1,3-D + Pic and dazomet at 35 gal/acre and 200 lb/acre, 5) propylene oxide at 45 gal/acre, 6) furfural + allyl isothiocyanate (AITC) at 600 lb/acre, 7) furfural and MNa at 56 and 50 gal/acre, 8) furfural + AITC at 400 lb/acre followed by four furfural applications of 6 gal/acre/injection, 9) furfural and MNa at 37 and 33 gal/acre followed by four furfural applications of 6 gal/acre/injection, 10) fosthiazate and Pic at 4.5 and 150 lb/acre, and 11) a nontreated control. The fumigation programs consisting of 1,3-D + Pic and dazomet, 1,3-D + Pic, Pic and MNa, and fosthiazate and Pic proved to be as valuable as the grower-standard MBr + Pic on strawberry plant vigor, sting nematode control, and early and total marketable yields.

Evaluation of Slow-release Fertilizers on Bell Pepper

This study was conducted to compare different formulations of a slow-release fertilizer with a conventional fertilizer program to determine their impact on yield and growth of bell pepper (Capsicum annuum). Two formulations of a methylene-urea slow-release fertilizer (Nitamin®) were evaluated on drip-fertigated and plastic-mulched bell peppers during 2006 in the eastern coastal plain and western Appalachian mountains of North Carolina. Liquid slow-release formulations were applied the first 6 or 9 weeks of the growing season and a dry formulation was banded at planting. Treatments were compared with the extension-recommended rate of 200 lb/acre nitrogen (N) (NC-200) and a high-input fertilizer rate of 300 lb/acre N (HI-300) from calcium nitrate injected in 12 weekly applications of drip irrigation. Irrigation was applied twice per week. The slow-release granular formulation at 200 lb/acre N produced the highest marketable yield and better canopy quality in eastern soil. Early marketable yield for this treatment accounted for 46% of the total yield. All slow-release treatments had higher N use efficiency (NUE) values than NC-200 and HI-300 in the eastern study. In loam soil (western study), pepper yield was statistically similar among treatments. Lower rates (150 lb/acre N) of slow-release fertilizer performed as well as NC-200 and HI-300 for marketable yield. Low rates (150 lb/acre N) of one of the liquid formulations performed better in total and marketable NUE than NC-200 and HI-300 in Fletcher, North Carolina. Liquid and dry formulations of slow-release fertilizer showed a potential to be used on bell pepper production across the state at reduced N rates, with greater impact on yield in coarse-textured soils found predominantly in the eastern coastal plain region.

Relationship of plant density to fruit yield of ‘Sweet Charlie’ strawberry grown in a pine bark soilless medium in a high-roof passively ventilated greenhouse

Eight plant densities (8.8, 9.5, 10.4, 11.4, 17.6, 19.1, 20.8, and 22.9 plants m −2) in 2001–2002 and 12 plant densities (8.8, 9.5, 10.4, 11.4, 12.7, 14.3, 17.6, 19.1, 20.8, 22.9, 25.4, and 28.6 plants m −2) in 2002–2003 were evaluated on growth and fruit yield of ‘Sweet Charlie’ strawberry ( Fragaria × ananassa Duch.) grown in a passively ventilated greenhouse. Plant densities were derived by varying within-row plant spacings (PS) (17.5 and 35 cm) with between row spacings (RS) (40, 45, 50, 55, 60 and 65 cm). Plants were grown in Polygal ® ‘Hanging Bed-Pack’ troughs filled with pine bark and fertigated with a complete nutrient solution. In 2001–2002, total marketable yield (g plant −1) or (no. fruit plant −1) were not influenced by RS. In 2002–2003, total marketable yield (g plant −1) or (no. fruit plant −1) were reduced at 40 cm RS, the narrowest RS used in the experiment. Early (November through January) and total marketable yields (g plant −1), crown diameter, and leaf number of plants grown at 35 cm PS were significantly greater than those of plants grown at 17.5 cm RS in both experiments. Total and early marketable yield (kg m −2) increased linearly as plant density (plants m −2) increased in both experiments. Winter strawberry production in a greenhouse using high plant densities and soilless substrates may be a viable alternative to open-field with methyl bromide fumigation production system.

Cover Crop and Pre-Emergence Herbicide Combinations in No-Tillage Fresh Market Cucumber Production

ABSTRACT A field study was conducted to determine the effect of various pre-emergence (PRE) herbicide (clomazone, ethalfluralin, and halosulfuron) combinations with or without a winter rye (Secale cereale L.) cover crop on control of smooth crabgrass [Digitaria ischaemum (Schreb. ex Schweig.) Schreb. ex Muhl.] and redroot pigweed (Amaranthus retroflexus L.) in no-tillage ‘Daytona’ cucumber (Cucumis sativus L.) production. Winter rye provided a significant advantage for weed control compared with the no-cover-crop production system. In the absence of herbicides, winter rye reduced redroot pigweed and smooth crabgrass densities up to 69 and 89%, respectively, compared with no winter rye at approximately 60 days after transplanting (DAT). Furthermore, the use of a winter rye cover crop increased the level of weed control achieved by herbicides at 56 DAT in two of three years for each weed species. Winter rye enhanced early marketable cucumber yields (from 2,008 to 6,100 kg·ha−1) under drought conditions in 2002, while winter rye suppressed early marketable yields (from 14,883 to 9,367 kg·ha−1 and 16,117 to 13,600 kg·ha−1 in 2003 and 2004, respectively) when sufficient moisture and cooler spring temperatures were present. During drought conditions in 2002, no-tillage treatments with clomazone + ethalfluralin and clomazone + ethalfluralin + halosulfuron produced similar yields; however, under high moisture and cooler conditions in 2003 and 2004, no-tillage treatments with clomazone + ethalfluralin + halosulfuron produced greater early- (∼16%) and total-season (∼25%) marketable yields than treatments with clomazone + ethalfluralin. Weed control is essential to obtain optimal cucumber productivity, as simple correlations indicated that cucumber yields were highly correlated to smooth crabgrass and redroot pigweed control. Cover crops, such as winter rye, can be integrated in vegetable production systems along with labeled herbicides as a sustainable approach to improved weed management.

Yield, quality and revenue of pickling cucumbers with irrigation and supplemental N fertilizer under a humid climate

A 5-yr field experiment was conducted in southern Quebec to investigate yield, gross revenue and quality of pickling cucumbers (Cucumis sativus L. ‘Fancipak’) in response to sprinkler irrigation. In addition, supplemental nitrogen treatments (40 kg ha-1 foliar and granular) following application of 80 kg ha-1 N preplant, as well as non-fertilized and over-fertilized controls (80 kg ha-1 N preplant, 40 kg ha-1 N granular and 60 kg ha-1 N slow-release) were compared in a 2-yr trial under irrigated and non-irrigated conditions. During 1997 to 2000, rainfall was close to or above normal and irrigation did not increase marketable yields. In 1999 and 2000, irrigation reduced early marketable yields relative to non-irrigated treatments. In 2000, a relatively cool year with average rainfall, there was a positive yield response to supplemental N in the non-irrigated plots, but not in the irrigated plots. In 2001, a very hot and dry season, irrigation increased early yield by 66%, marketable yield by 160% and gross revenue by 164% compared with non-irrigated treatments. Non-irrigated treatments did not respond to supplemental N, but supplementing the irrigated treatments with 40 kg ha-1 of N increased marketable yields by 22%, generating 18% additional revenues. Applying N in either a foliar or granular form gave similar results. Overall, under a humid climate, irrigation only had a positive impact on gross crop revenue for pickling cucumbers in 1 out of 5 yr. Key words: Cucumis sativus, pickle, overhead irrigation, sprinkler, foliar nitrogen, granular nitrogen, slow release.

Performance of Containerized and Bare-root Transplants with Soil Fumigants for Florida Strawberry Production

Field studies were conducted in three Florida locations (Bradenton, Gainesville, and Quincy) during 1998-99 and 1999-2000 to: 1) compare the performance of two transplant systems under diverse MBr alternative programs in `Chandler' strawberry (Fragaria ×ananassa), and 2) determine the efficacy of these treatments on soilborne pest control in strawberry. Fumigant treatments were: 1) nonfumigated control, 2) methyl bromide plus chloropicrin (MBr + Pic) at a rate of 350 lb/acre, 3) Pic at 300 lb/acre and napropamide at 4 lb/acre, 4) 1,3-dichloropropene (1,3-D) plus Pic at 35 gal/acre and napropamide at 4 lb/acre, 5) metam sodium (MNa) at 60 gal/acre and napropamide at 4 lb/acre, and 6) MNa followed by 1,3-D at 60 and 12 gal/acre and napropamide at 4 lb/acre, respectively. Strawberry transplants were either bare-root or containerized plugs. There were no significant fumigant by transplant type interactions for strawberry plant vigor and root weight per plant, whereas ring nematode (Criconema spp.) and nutsedge (Cyperus rotundus and C. esculentus) populations, and total marketable fruit weight were only infl uenced by fumigant application. The nonfumigated plots had the lowest strawberry plant vigor and root weight per plant in all three locations. In most cases, plant vigor and root biomass per plant increased as a response to any fumigant application. With regard to the transplant type, bare-root transplants had similar plant vigor as plugs in two of the three locations. Fumigation improved nutsedge and ring nematode control. All fumigants had higher early and total marketable yield than the nonfumigated control, whereas transplant type had no effect on total fruit weight.

Initial Crown Diameter of Transplants Influences Marketable Yield Components of Two Strawberry Cultivars in Annual Hill Production System

Influence of initial transplant size on yield components was investigated using two strawberry cultivars over a three-year period. Plants were sorted into three groups according to crown size each fall before transplanting. Fruits were harvested once a week over a ten-week period each year. There were marked differences between ‘Chandler’ and ‘Camarosa’ cultivars. Transplants of the ‘Chandler’ cultivar with larger crown diameters produced significantly greater early and total marketable yield than transplants with smaller crown diameters. Regression analysis of yield components against initial crown diameter revealed a positive relationship between total fruit numbers produced per plant and initial crown size for both cultivars. Total weight of marketable fruit produced per plant was positively associated with initial crown diameter of transplants. Relationships between initial crown diameter and early yield components were not as consistent among the two cultivars tested. Early yield components of ‘Chandler’ were all correlated to initial crown diameter of transplants. The size of the transplant did not influence early yield components of ‘Camarosa’ except for fruit size. There was a significant relationship between the postharvest dry weight of plants and initial crown diameter of transplants.

(182) Delayed Planting and Plug Cell Volume Effects on Growth, Development, and Yield of Transplanted Sweet Corn

Transplanting sweet corn is commonly practiced in the northeast U.S. to improve stand establishment and promote early harvest. However, early spring storms and labor constraints can delay transplanting when establishment is most desirable. `Temptation' sugary enhanced (se) sweet corn transplants 0-, 2-, 4-, 6-, and 8-days-old beyond the “grower” 2-week growth period were field planted to explore the effects delayed planting combined with plug cell volume differences would have on transplant ear quality and early yields. The transplant treatments were evaluated in a two-way factorial (five delayed planting dates × three plug volumes) arranged in a split-plot design with five replications. Field sites were the whole plot treatment and the factorial treatments were the split-plots. All transplants were planted on 24 May 2004 at the two field sites. The final density was ≈22,000 plants/acre. Transplant cell volume (15, 19, and 29 mL) had no significant effect on ear quality and total marketable yield. Ear length was significantly affected by field site (P≤ 0.0001) and ear diameter was significantly affected by planting delay (P= 0.0145). Field site (P≤ 0.0001) and planting delay (P= 0.0090) both significantly affected the number of early marketable ears/acre. The results indicate that transplants can remain in the plug cells up to 20 days (2 weeks + 6 day delay) before the delay negatively impacts ear diameter, tip fill, and early marketable yield.

(370) In-row Plant Spacing Affects Early Season Fruit Yield of Strawberry Grown in a Winter, Annual Hill Production System

On standard two-row black polyethylene covered beds, `Camarosa', `Rosa Linda', and `Sweet Charlie' strawberry plants were grown at 23, 31, 38, or 46 cm within-row spacing during the 1997–98 and 1998–99 seasons at Dover, Fla. Ripe fruit were harvested twice weekly from December through March. The first 8 weeks of harvest was considered the early period; the late period consisted of all harvests after the first 8 weeks. The effect of spacing on early marketable yield was consistent across seasons and cultivars. The 23-cm spacing resulted in the highest marketable yield per unit area, followed by the 31-, 38-, and 46-cm spacing. The percentage of fruit that were small (unmarketable) was higher at the 23-cm spacing than at the wider spacings (40% vs. 35% or 36%), but spacing did not affect the percentage of fruit that were misshapen. For the late harvest period, a spacing effect on marketable yield occurred in 1998–99, but not in 1997–98. The 23-, 31-, and 38-cm spacings in 1998–99 resulted in similar late period yields, which were 15% to 21% higher than the yield resulting from the 46-cm spacing. These results indicate that marketable yields per plant during the late period were higher at the wider spacings.

Red and Black Mulch Color Affects Production of Florida Strawberries

Strawberries (Fragaria ×ananassa, Duch) were grown in the annual hill system at four locations in Florida to compare the effects of standard black low density polyethylene (LDPE) mulch and red reflective mulch (SMR-red) on fruit size and production. Marketable fruit size was not affected by mulch color. Early and total marketable fruit yields were not affected by mulch color at Bradenton, but yields were significantly higher at Gainesville with red than black mulch, and were significantly higher with black than red mulch at Quincy and Hastings. Soil temperatures under the black mulch were significantly higher than red mulch at Hastings but significantly higher under red than black mulch at Gainesville. Mean soil temperatures at soil depths of 5 to 25 cm ranged from 0.2 to 0.4 °C Reflected photosynthetically active radiation values at 25 and 50 cm above the mulch were higher earlier in the season and decreased as the season progressed. Within a month after transplanting when foliage covered about 10% of the mulch, reflections were lower and similar at both heights with black mulch than red and were higher at 25 than 50 cm with red mulch. Data indicate that there was not a consistent advantage of the use of this red mulch over black mulch at four locations in Florida.

Yield and Quality of Triploid Watermelon Cultivars and Experimental Hybrids Grown in Mississippi

Evaluations of 21 entries (commercial cultivars and breeders' experimental hybrids) of triploid watermelon (Citrullus lanatus) were conducted in northern and central Mississippi during 2000 and 2001. The purpose of this research was to identify high-yielding, medium-sized triploid cultivars with good horticultural characteristics and consumer qualities for commercial production in Mississippi. Most entries were similar to `Tri-X 313' and had red flesh, oval shape, and a mottle stripe rind pattern. SXW 5052, `Triple Crown,' `Crimson Trio,' `SeedWay 4502,' and `Millionaire' produced the highest total marketable yields; however, SXW 5052 is no longer available. `Crimson Trio' produced slightly smaller-sized melons compared to other entries and `SeedWay 4502' produced melons with relatively low soluble solids concentration. Based on total marketable yield, average size of melons, soluble solids concentration, and lack of undesirable characteristics such as hollowheart, black and colored seed, and rind necrosis, `Triple Crown,' `Millionaire,' `Cooperstown,' `Summer Sweet 5244,' and `Crimson Trio' can be recommended as mid- to late-maturing cultivars for commercial production in Mississippi. Based on early marketable yield, and using the same criteria listed above, `Tri-X 313' and `Tri-X Carousel' can be recommended as early-maturing cultivars for commercial production in Mississippi. `Tri-X 313' exhibited only one undesirable trait, producing a relatively high number of black and colored seeds. `Diamond' had high early and total yields, as well as high soluble solids concentration, but it should be recommended only on a trial basis to determine its potential susceptibility to hollowheart.

Suppression of Watermelon Mosaic Virus in Summer Squash with Plastic Mulches and Rowcovers

Plastic mulches and rowcovers were evaluated in southern Illinois to determine their influence on watermelon mosaic virus (WMV) disease incidence and symptom severity in susceptible and tolerant summer squash (Cucurbita pepo). The use of either black or white mulch produced greater early and total marketable yields than no mulch (bare soil) on `Dividend' and `Multipik'. More fruit had WMV symptoms with no mulch than with mulch, regardless of cultivar. However, more severe WMV symptoms developed on the fruit of susceptible `Multipik' compared to tolerant `Dividend'. The use of plastic mulches provided greater and longer protection to `Dividend' compared to `Multipik'. However, `Dividend' fruit did eventually develop virus symptoms as disease incidence in production fields increased. Rowcovers reduced the number of alate aphids landing on plants which resulted in fewer plants with WMV symptoms and suppression of symptoms on squash plants regardless of mulch type. Rowcovers had a greater influence on reducing the incidence of WMV and the severity of symptoms on `Dividend' compared to `Elite'. Rowcovers did not reduce WMV on `Elite' by the end of the season and were more effective when used with white mulch compared to black mulch. Rowcovers suppressed the incidence and severity of WMV symptoms that developed on a virus tolerant squash cultivar for a greater length of time compared to a susceptible cultivar, which related to increased yields and fewer culls with virus symptoms on the tolerant cultivar.

Bloom and Postbloom Applications of NAD/NAA Mixture Have Minimal Effects on Yield and Fruit Size of Field-grown Tomatoes and Peppers

A commercial mixture of 1-naphthaleneacetamide and 1-naphthaleneacetic acid (Amcotone) was applied to tomato (Lycopersicon esculentum Mill.) and pepper (Capsicum annuum L.) at various timings from early bloom through early fruit development to evaluate effects on fruit size and both early and total marketable yield. Amcotone was applied at rates from 10 to 40 mg·L-1, at three sites for each of the species studied. Measured yield response variables in tomato did not differ between the control and Amcotone treatments, regardless of location. Amcotone treatments did not affect yields or fruit size for pepper at the New Jersey or Texas sites. However, at Ft. Pierce, Fla., early marketable yield of pepper was increased in plots receiving three Amcotone applications at 10 mg·L-1, but total marketable yield was significantly reduced in all plots receiving more than two Amcotone sprays, and mean fruit weight was reduced by all Amcotone treatments. Early and total marketable yield of pepper at Ft. Pierce were markedly reduced in plots receiving four applications of 40 mg·L-1, which was a high rate used to assess potential phytotoxicity. While minimal benefit from auxin application was observed in this study, earlier studies suggest that these results may have been influenced by favorable environmental conditions for fruit development or negative effects on unopened flowers during all Amcotone spray applications.

Effects of supplemental lighting and cover materials on growth, photosynthesis, biomass partitioning, early yield and quality of greenhouse cucumber

Seedless cucumber ( Cucumis sativus L.) cv. Flamingo was grown in winter time in glass, double-inflated polyethylene (D-poly) and twin-wall acrylic (acrylic) greenhouses with or without 16 h (3:00–19:00 hours) of supplemental lighting to investigate the effects of the cover materials and supplemental lighting on plant growth, photosynthesis, biomass partitioning, early fruit yield and quality. Supplemental lighting promoted plant development and increased leaf chlorophyll, leaf photosynthesis, plant biomass and early marketable yield production. Supplemental lighting also increased biomass allocation to fruit, fruit dry matter content and skin chlorophyll content. There was little difference in leaf photosynthesis rates of plants under the three cover materials although solar irradiance on sunny days was much higher in glass than in D-poly houses. Dry matter production of plants grown in glass houses was higher than in D-poly and acrylic houses, but dry matter partitioning was not different under the three greenhouse covers. The high dry matter production in glass houses was translated into high fruit dry matter content, but not high early marketable yield. Cucumber early marketable yield in glass houses was similar to that in D-poly but lower than in acrylic houses. The supplemental lighting sufficiently compensated for the loss of solar radiation in D-poly and acrylic houses.

Fertilizer Substitutions in Hydroponically Grown Greenhouse Tomatoes

Experiments were carried out to evaluate two salts, K2SO4 and NaCl, as materials to supplement the electrical conductivity (EC) of the basic nutrient solution in nutrient film technique (NFT). The effects of these materials on the growth, yield and fruit quality of greenhouse tomato (Lycopersicon esculentum Mill.) grown by NFT were quantified. These effects were tested by increasing the recirculating solution EC from a base value of 1500 μS·cm-1 to that suitable for the crop growth stage with normal feed (macronutrients), 0.38 m (0.53 lb/gal) K2SO4 or 1.14 m (0.55 lb/gal) NaCl, at a common pH of 6.2. In 1995 and 1996, there were no significant effects of the treatments on crop growth. In 1995, the early marketable yield was significantly lower when K2SO4 was used but the yield at the end of the season did not differ among the treatments. Furthermore, with K2SO4, the proportion of grade #1 fruit in early total yield was lower than in the control, while, fruit biomass content was higher than in the NaCl treatment. In 1996, the cumulative marketable fruit weight was unaffected by the treatments. A trend toward high number of large grade fruit occurred with the NaCl treatment. The pH and EC of the fruit homogenate were favorably affected by the NaCl treatment. Adding K2SO4 or NaCl in partial substitution of macronutrients in the recirculating solution may have a role in NFT systems in not only reducing environmental pollution (from nitrates and phosphates) and fertilizer costs, but also in improving fruit quality and, therefore, profit margins.

Mulch Type Influences Yield of Fall Tomato

Because of environmental concerns relating to the potential for surface runoff from plastic culture, the potential of six cover crops [pearl millet (Pennisetum glaucum), sorgham (Sorghum bicolor), cowpea (Vigna sinensis), buckwheat (Fagopyrum esculentum), soybean (Glycine max), and millet/cowpea combination was compared to a plastic mulch for fall tomato production in 1996. All cover crops were chemically desiccated prior to tomato transplanting. The use of plastic mulch significantly increased early marketable yield; soybean or millet/cowpea mulch significantly reduced the production of large fruit. Total marketable yield of cover crop mulches except millet/cowpea was similar to that of plastic mulch. In 1997, full (0.9-m) and narrow (0.45-m) plastic mulched beds were compared to desiccated millet or sorghum mulches or straw mulch applied at planting. Early marketable yield was greatest for straw mulch. Total marketable yield of straw and both plastic mulch treatments was significantly higher than that for desiccated mulches. Width of the plastic mulched bed did not significantly affect total marketable yield.