Row Cover Research Articles

冬期におけるＰＶＡフラットヤーンを使用したべたがけ資材下の微気象特性

We compared the effects of heat retention of the row cover material ‘PVA flat yarn fabric’ with that of PVA non-woven fabric (trade name Tuffbell) from December to January. A tunnel-shaped floating row cover (1 m wide and 30 cm high in the middle) was installed in an open field, and the internal microclimate was measured. PVA flat yarn fabric is made from flat plate-like fibers (6 or 7 mm wide) propped up straight with polyethylene line. Four vacant space rates (22%, 33%, 56%, and 67%) were set up by changing the intervals of the flat yarns, whereupon the following finding became clear.1) On sunny days, the smaller the vacant space rate of the material, the higher the air and soil temperature under the row cover rose in the daytime, although conversely, both dropped at night.2) The difference in air temperature between the inside and outside (row cover-no cover) decreased as the wind velocity increased from 0 m/s to 0.7-0.8 m/s, although the air temperature under the row cover at night rose, when the wind velocity exceeded a certain figure.3) Materials most closely akin to Tuffbell 3800N with respect to the beneficial effects on temperature under the row cover were the PVA flat yarn fabric, the vacant space rates of which were 56% and 67%. The PVA flat yarn fabric was considered to be usable as a substitute for PVA non-woven fabric.4) When the vacant space rate of PVA flat yarn fabric exceeded that of PVA non-woven fabric, an equivalent effect on heat retention was obtained. This may encourage the development of novel materials with good ventilation and the use of PVA flat yarn for the purpose of heat retention.

Occurrence of Damping-off on Okra in Gunma Prefecture, and Control Effect on Disease by Change of Sowing Time and Row Cover with Nowoven Fabric

Occurrence of Damping-off on Okra in Gunma Prefecture, and Control Effect on Disease by Change of Sowing Time and Row Cover with Nowoven Fabric

Plastic Mulches and Row Covers on Growth and Production of Summer Squash

ABSTRACT Row covers and colored plastic mulch are used routinely throughout the United States to grow vegetables but are rarely used in conjunction to produce a crop. Summer squash (Cucurbita pepo L.), cv. Prelude II, was grown on an Orangeburg sandy loam soil in Shorter, AL. The summer squash was direct seeded in single rows. The experiment consisted of 12 treatments including: (1) black plastic mulch (BPM)+spunbonded row cover (RC), (2) BPM alone, (3) white plastic mulch (WPM)+RC, (4) WPM alone, (5) red plastic mulch (RPM)+RC, (6) RPM alone, (7) bare soil (BS)+RC, (8) BS alone, (9) silver plastic mulch (SPM)+RC, (10) SPM alone, (11) blue plastic mulch (BLUPM)+RC, and (12) BLUPM alone. Year and mulch color affected all variables, row cover affected plant height and stem diameter, and the mulch color × row cover interaction affected yield variables. Mulch color and year significantly affected air and soil temperatures and row cover significantly affected air temperature. Soil temperatures were more than 5°C lower than air temperatures in all treatments and air temperatures were 2–5°C higher with row covers than without. Increased soil and air temperatures did not always result in yield increases. Colored plastic mulch with or without row covers did not increase early fruit yield in squash. Lack of a mulch/row cover induced temperature effect on yield was attributed to the relatively high mean air temperatures that may have masked treatment temperature effects.

The Effect of Variable Seed Rate Proportions on Agronomic Attributes, Dry Matter Production, Biological Potential and Economic Viability of Some Grass-Legume Mixed Pastures

An experiment was conducted to assess the agronomic attributes, dry matter (DM) yield, biological potential and economic viability of grass-legume mixtures at Haramaya University in Ethiopia during 2004 and 2005. Chloris gayana, Panicum coloratum, Melilotus alba and Medicago sativa were planted as pure stand and in mixtures using 50:50, 33: 67, 67: 33, 25: 75 and 75: 25 seed rate proportion to give 24 treatments in a randomised complete block design with 3 replications. There were significant (P < 0.05) differences in the number of seedlings per m2 (SLM), row cover, number of tillers per m2, days to 50% flowering (DF 50%) of the grass components among the grass/legume combinations due to seed rate proportions. Moreover, SLM, the number of branches per m2, the height of the plant at harvest, DF 50% of the legume components were significantly (P < 0.05) affected among the mixtures due to seed rate proportions. There was a significant (P < 0.05) difference in the DM yield of pure stand grasses and legumes, and their mixtures due to seed rate proportion. Significant (P < 0.05) effects were also observed on the relative yield (RY), the relative total yield (RTY), the relative crowding coefficient (RCC) and the aggressivity index of both the grass and legume components and their mixtures due to different seed rate proportions throughout the study. The two years\' mean RTY of all grass-legume mixtures were greater than one (range: 1.23-2.11) and Chloris mixed with Melilotus and Medicago with 67: 33 seed rate proportion had higher RTY than other mixtures. Both the grass and legume components in the mixture produced mean RCCs values in excess of unity and almost equal values in both components, indicating that all yielded better in the mixture than expected in pure stands at different seed rates. Chloris gayana mixed with Melilotus alba at 50:50 and 33:67 seed rate proportion gave higher DM yield, average net return/ha and average net return/ha/yr compared to pure stand grasses and legumes and their different mixtures during the study. Therefore, to alleviate the feed scarcity in the area; these grass-legume mixtures could be introduced to smallholder farms. In addition, further studies on animal performances should be conducted using feeding trials and under grazing conditions. Keywords: Agronomic Attributes; Biological Potential; Dry Matter Yield; Economic Viability; Grass/Legume Mixture; Seed Rate Proportion East African Journal of Sciences Vol. 2 (2) 2008: pp. 95-104

Rowcovers Improve Winter Survival and Production of Western Trailing ‘Siskiyou’ Blackberry in the Eastern United States

Winter injury has limited the expansion of commercial blackberry (Genus Rubus, subgenus Rubus) production into more northern latitudes in central and eastern United States. Rowcover (RC) was applied over trailing ‘Boysenberry’ and ‘Siskiyou’ and erect, thornless ‘Triple Crown’ and ‘Apache’ blackberries at Kearneysville, WV (lat. 39.5°N, USDA Plant Hardiness Zone 6b) from 2004 to 2007. The daily minimum temperatures under RC were as much as 5 °F to 10 °F higher at nights after sunny days, but were similar during nights after overcast days. On sunny days, daily maximum temperatures under RC were as much as 28 °F higher than in the open. Under RC, humidity rose more quickly and remained higher during the day than in the open, but was slightly lower at night. Mean vapor pressure deficit in late December, January, February, and early March was 100 to 250 kPa higher under RC than in the open. RC treatment significantly reduced winter injury and increased yield in ‘Siskiyou’ blackberry plants. The winter protection techniques described here would provide substantial benefits for growing blackberries in more northern areas where winter injury frequently causes crop failure.

Sweetcorn production from transplants

In our trial we tried to find out how the time of propagation and transplanting influenced the growing season of sweet corn along with some major properties relevant to quality. The following technological variations were compared with the help of the variety Spirit (normal sweet, very early ripening): transplanted plants with floating row cover (with 2 planting dates); transplanted plants with no row cover: direct seeded plants with no row cover. The 21 day transplant growing period reduced the growing period by 16 to 20 days, compared to the technology used in the existing practice of production. Earliness had a negative influence on ear size, nonetheless it is worth while to attempt since the market is not so exacting with new products in the early period. Covering the seedlings in the early season was clearly beneficial, as the floating row cover provided protection for plants against lower night temperatures which are common in this period.

EFFECT OF PROPAGATION TIME AND METHOD ON SWEET CORN MORPHOLOGY

In our experiments, we tried to find out how the method and time of propagation, out of the technological elements applied by us for enhancing earliness, influenced some of the morphological characteristics of sweet corn. The test variety was Spirit, a normal sweet variety. The following treatments were applied during the experiment: P1 = uncovered direct seeded plants (Apr 6th) P2 = covered direct seeded plants (Apr 6th) P3 = covered transplanted plants (Apr 6th) P4 = uncovered direct seeded plants (Apr 20th) P5 = covered direct seeded plants (Apr 20th) P6 = uncovered transplanted plants (Apr 20th) P7 = covered transplanted plants (Apr 20th) At the first top dressing 20 ears were selected from each treatment in a random fashion and the following measurements were carried out after harvest: plant height (to flag leaf, after harvest), stem diameter (under the ear in ripening phase), number of tillers and ear node height. Direct seeding resulted in a significantly larger stem diameter, in a greater ear node height, in an increased number of tillers and, in combination with early propagation, in a greater plant height. Early propagation resulted in a lower ear node height and, in the case of direct seeding, in a greater stem height, in a lower number of tillers and, in the stand with row cover, in a smaller stem diameter as compared to the common (Apr 20th) propagation date. The transplanted treatments with cover showed practically no evidence of tillering. From the point of the effect of the propagation method we compared the results of the treatments P2-P3 at the earlier date, while those of P5-P7 and P4-P6 at the later date. In the investigation of the effect of propagation date we compared the treatments P1-P4, P2-P5 and P3-P7.

Organic Garlic Research in Colorado; Winter Mulching, Irrigation Systems, Spacing, Scape Removal, and Flame Cultivation

The Specialty Crops Program at Colorado State University conducted research of hardneck garlic (Allium sativum ophioscorodon) production on certified organic land at the Horticulture Field Research Center northeast of Fort Collins, Colo., during the garlic growing seasons of 2002–03 and 2003–04. Winter mulches and irrigation treatments were studied during the first season. It was found that garlic that was covered by any type of winter mulch (grass hay, single or double layers of floating row cover) resulted in better yields (higher average bulb weight) than garlic which was not covered at all (ANOVA, F = 2.93, P = 0.034). Yields from sprinkler and furrow irrigation were essentially the same; however, furrow irrigation used nearly 30% more water. Too little water was applied to the drip-irrigated treatment and yield suffered. Our findings suggest that yields are negatively impacted when less than 12 inches of combined precipitation and irrigation are received. During the second season, clove planting spacings of 3, 4.5, and 6 inches, and flame weeding and scape removal effects on yields were studied. The bulbs that grew at a 6-inch spacing were significantly larger than those grown at 3 and 4.5 inches (ANOVA, F = 46.5, P &lt; 0.001). Flame weeding had no significant effects on yields (t-test, P = 0.6) and may be more economical compared to hand weeding depending on fuel costs. Removing the scapes did result in slightly higher bulb weights (t-test, P = 0.06). Removing scapes takes extra labor and may not be worth the time for only slightly higher bulb weights; however, selling the edible scapes may offset the cost and generate extra income.

Alternative Management Tactics for Control of &lt;I&gt;Phyllotreta cruciferae&lt;/I&gt; and &lt;I&gt;Phyllotreta striolata&lt;/I&gt; (Coleoptera: Chrysomelidae) on &lt;I&gt;Brassica rapa&lt;/I&gt; in Massachusetts

The flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae: Alticinae) are significant pests of crops in the Brassicaceae family. From 2001 to 2003, the efficacy of both new and commonly used treatments for the control of flea beetles in brassicas, Brassica rapa L., were evaluated in three small plot, randomized complete block design trials. Row cover and carbaryl (applied as a weekly foliar spray) were found to be the most consistent at reducing damage in comparison with untreated controls in all trials. Two new products that may provide adequate flea beetle control are spinosad (in either conventional or organic formulations) and thiamethoxam. The plant-derived compounds azidiractin and pyrethrin did not protect treated plants from flea beetle feeding. Treatment of plants with kaolin, or removal of the beetles with a vacuum, also did not reduce the level of crop damage. The level of damage at harvest was found to be correlated with population size of flea beetles in each plot, as measured by captures on yellow sticky traps and direct visual counts. Removal of the outer two leaves of individual B. rapa plants reduced the total number of holes per plant by 40%, while only removing 15% of the leaf area.

In vitro culture response of apical and axillary shoot-tips excised from crisphead lettuce cores depends on head maturity, not storage time

Successful lettuce (Lactuca sativa L.) breeding requires assessment, selection, and reseue of germplasm from field-grown plants during a limited period of time. Tissue culture methods have proved successful in rescuing selected lettuce genotypes and producing seeds in a disease-free environment. The present study was conducted to determine the response of the apical and axillary shoot-tips of lettuce to storage duration prior to in vitro culture. The study focused on core length as a source of variation between maternal explants. Advanced maturity was obtained by applying an agrotextile row cover over lettuce plants. Apical and axillary buds were derived from covered lettuce with long cores (46±0.8 mm) and from non-covered lettuce with short cores (30±0.7 mm). The cores were stored at 2°C for 0,2, or 13d. Apical and axillary shoot-tips were removed from the cores and placed onto MS medium. After 3 mo. of growth culture, twice as many leaf primordia (6.6 leaves) developed from the apical shoot-tip as compared to those from the axillary shoot-tip (3.0 leaves). More shoot-tips survived when excised from short cores (83%) than when excised from long cores (71%). Root formation was affected by the source of shoot-tip and the size of donor explant. Three times more explants from apical shoot-tips and short cores rooted (71%) than did explants from apical shoot-tips and long cores (27%) or explants from axillary shoot-tips (long cores, 14%; short cores, 19%). Storage of cores for up to 13 d had no effect on the survival rate of shoot-tips, nor on shoot or root formation, suggesting that cores of lettuce plants can be stored prior to in vitro micropropagation without significant loss of regeneration efficiency.

Efficacy of Selected Insecticides for Management of the Multicolored Asian Lady Beetle on Wine Grapes Near Harvest

As one component of an Integrated Pest Management program for Midwestern wine grapes, we examined the efficacy of several insecticides on adults of the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). For field trials, percentages of clusters with at least one H. axyridis were recorded for each plot before treatment and on the day of harvest. We also examined the efficacy of insecticides under laboratory conditions via two routes of exposure, topical application and insecticide residues. In the 2004 field trials, the percentage of clusters infested with H. axyridis adults at harvest was statistically lower in plots treated with bifenthrin applied 7 days before harvest (DBH), carbaryl 10 DBH, and in plots covered with floating row cover compared to the untreated plots. In 2005, the percentage of clusters infested with H. axyridis adults at harvest in plots treated with zeta-cypermethrin 7 DBH, bifenthrin 22 and 7 DBH, and imidacloprid 1 DBH was statistically lower than beetle infestation in the untreated plots. In the laboratory, bifenthrin, carbaryl, and thiamethoxam were lethal to H. axyridis adults 7 days after treatment. Based on the efficacy results, labeled insecticides, pre-harvest intervals, and the late-season influx of H. axyridis infestations, chemical control is currently limited to carbaryl, malathion, and/or imidacloprid.Accepted for publication 13 June 2006. Published 3 October 2006.

Polypropylene Row Covers Greatly Enhance Growth and Production of Fourth-leaf Sweet Cherry Trees

Black, woven polypropylene row covers were compared to chemical sprays as methods to manage ground vegetation in a `Regina'/Gisela 6 orchard planted in 2001. Row covers were installed within 1 month of planting. Exposed row cover width was 2.4 m, with edges (30 cm on each side) buried in the ground. Only a 30-cm band along the edge of row covers was sprayed with herbicide to facilitate mowing. Weed management of control trees consisted of chemical herbicide sprays. Trees were not fertilized since planting in 2001. Irrigation of all trees was applied with low volume (20 L·h-1) microsprinklers and scheduled according to soil water content. Row covers significantly increased trunk cross-sectional area (TCSA) by about 30% annually. By Summer 2004, trees with ground covers had filled their allotted space within rows, while control canopies were ≈50 cm apart. Trees in row covers produced a 130% higher average yield than controls (7.4 kg/tree vs. 3.2 kg/tree). Row covers produced larger and firmer fruit, which matured 2–3 days later than controls. Groundcovers slightly increased soil temperature from April to September by ≈2 °C at 5- and 10-cm depths. Roots under ground covers were denser and more spread out than in controls and water use efficiency was higher for trees growing in ground covers. Amount and labor for herbicide application was reduced to less than half with row covers. Although ground covers are expensive at ≈$2000 per acre, their cost could be offset by earlier and higher production and by long-term savings in labor, water use, and herbicides. Durability of row covers is expected to exceed 15 years.

(204) The Effect of High Tunnels and Row Covers on Air Temperatures and Spring-planted Tomato Yield in Louisiana

Tomato is an important vegetable crop in Louisiana for small- to large-scale growers. Growers often use protected cultivation with structures, such as greenhouses, in order to take advantage of higher prices early in the season and increase profits through increased tomato yield and quality. A negative aspect of greenhouse use is the high investment and production costs associated with these structures. High tunnels, or simple greenhouse-like structures, have been used to protect crops from cold temperature in northern states, as they often provide benefits similar to greenhouses with considerably lower cost. Very little research has been conducted on the use of high tunnels for crops in the southern states. High tunnels in combination with row covers were evaluated for field cultivation of spring season fresh market tomato in Louisiana. The studies were set up in a randomized complete-block design with three replications. Tomatoes were transplanted into single rows on four-row raised beds covered with black plastic mulch on 1.2-m centers on 13 Mar. 2004. Row covers were installed immediately after transplanting and removed on 3 May. Plants were harvested for 6 weeks starting 12 May 2004. Both high tunnels and row covers significantly increased minimum and maximum air temperatures at a 15-cm height compared to the black plastic mulch control. Early yield was highest with the tunnel treatment without row cover compared to tunnel with row cover and similar to row cover alone or the control. There were no differences in total marketable yield between treatments. Research results from 2 years will be presented.

(206) Control Methods for Mexican Bean Beetle (EpilachnavarivestisMulsant) Infestations on Snap Bean (PhaseolusvulgarisL.) Crops

Three different control methods, row cover, staggered plantings, and the release of a parasitic wasp, Pediobiusfoveolatus, were used to test effectiveness at controlling Mexican bean beetle (MBB) infestations on snap beans. The study consisted of six plots, on five different farms in the Morgantown, W. Va. area, three with and three without the application of the control methods. Releases of 15 adults and 100 larvae during flowering of the bean crop occurred at each plot. Weekly counts of the three MBB life stages, parasitized MBB larvae, and bean yields were taken. The results showed that the release of the parasitic wasp maintained the MBB populations below economic thresholds throughout the growing season. The average yield from plots that received wasp treatments was 34.2 kg, compared to 15.2 kg harvested from untreated plots. Plots that received row cover treatments were shown to be slightly more effective than staggered plantings at controlling MBB populations. Row cover plots yielded an average of 15.3 kg, in comparison to the 11.8 kg yield from untreated plots, while staggered plantings in treated plots yielded 9.5 kg, compared to 6.0 kg from untreated plots. End of season MBB populations in treated plots consisted of 75 adults, 57 pupae, 275 larvae, and 94 parasitized larvae compared to untreated populations, 98 adults, 214 pupae, 420 larvae on average. In conclusion, increased yields can likely be correlated to decreased MBB populations, indicating the release of P. foveolatusas a viable option for control of MBB, especially in organic systems.

Row covers for quality improvement of Chinese cabbage (Brassica rapa subsp. Pekinensis)

Row covers of polypropylene sheeting have been studied in relation to the quality in Chinese cabbage (Brassica rapa subsp. Pekinensis ’Nagaoka 50') for 3 years (1999, 2000, and 2001) in the area of Granada, Spain, under a Mediterranean continental temperate climate, on 55‐day cycles with transplanting in mid March. The mean commercial yield for the 3 years was 11.9 kg m–2 under row covers, but only 2.1 kg m–2 in open air, owing primarily to the important number of non‐commercial cabbages. The cabbages grown in the open air were exposed to lower temperatures than under covers and showed a higher number of plants with bolting and plants lost in the field. The better thermal regime under the covers and the least vapour pressure deficit favoured heading, reducing the number of malformed cabbages. The foliar calcium (Ca) content in the outer leaves was significantly greater in the open air than under the row cover, whereas the reverse was true in the inner leaves. These lower Ca contents in the inner leaves of the open air plants, encouraged tipburn. The use of the row cover constitutes a low‐cost technique to improve open air spring cultivation of this leafy vegetable in this type of Mediterranean continental climate.

Effect of a Synthetic Fabric Row Cover on Soil Moisture Content, Growth and Fruiting of Young Sweet Cherry Trees (Prunus avium L. cv. `Regina'/Gisela 6)

A `Regina'/Gisela 6 sweet cherry orchard was planted in April 2001 to evaluate a row cover (RC) made of black, woven polypropylene fabric, in water conservation. Trees were trained to a central leader and planted at 3 m x 5.4 m. Soil water content and tree growth variables were compared for trees growing with or without a 2.4 m-wide RC. Irrigation of all trees replenished approximately 80% of weekly evaporation rate. Trees with RC maintained consistently higher (30% to 40%) soil moisture content at 30 cm depth than non-RC trees. In Spring 2003, trees in RC had significantly larger trunk cross sectional area (34%), height (7%), total wood length (65%), total number of branches (20%) and number of 1-year-old-shoots (45%) compared to trees with no row cover. Length of 1-year-old wood for trees in RC was two-fold that of non-covered trees. In Summer 2003, RC had no clear effect on bloom time, intensity or duration. Fruit yields were light and not affected by RC, but fruit size was slightly larger for trees in RC. Although trees were not fertilized, foliar nitrogen content was significantly higher and leaf green color was notably darker green for trees with RC. During Spring and Summer 2003, soil temperatures under RC at 5-cm and-10 cm depths were generally 1 °C to 2 °C warmer than in non-covered ground. The RC did not affect air temperature at 10 cm and 30 cm above ground. It is speculated that RC promoted tree growth by a combined increased available soil moisture and warmer root temperatures, which favor root development and nutrient uptake, particularly in the absence of competing weeds. Increased branching in trees with RC is unclear. It is possible that light quality above RC triggers developmental changes resulting in increased vegetative budbreak.

Interação genótipo x ambiente em cultivares de alface na região de Jaboticabal

Estudou-se a interação genótipo x ambiente de doze cultivares de alface, sendo quatro do grupo lisa (Babá de Verão, Karla, Nacional e Elisa), quatro do grupo crespa (Simpson, Hortência, Verônica e Grand Rapids) e quatro do grupo americana (Laidy, Tainá, Lucy Brown e Raider). Os tratamentos foram constituídos pelo cultivo da alface em dez ambientes (casa de vegetação, túnel baixo de cultivo, túnel baixo com sombrite, agrotêxtil e campo, na presença e ausência de mulching). Foram utilizados dois períodos de cultivo, agosto a novembro de 2001 e março a junho de 2002 em Jaboticabal. Cada experimento (ambiente de cultivo) foi conduzido utilizando-se o delineamento de blocos casualizados, com doze cultivares e três repetições. A análise de variância conjunta demonstrou valores de F significativos (p&lt;0,01) para a interação genótipo x ambiente. Para o cultivo de agosto a novembro/2001, as melhores respostas foram obtidas para as cultivares do Grupo Lisa, nos ambientes casa de vegetação com mulching, túnel baixo de cultivo sem mulching e campo sem mulching. Todas as cultivares apresentaram piores desempenhos nos ambientes túnel com sombrite sem mulching, agrotêxtil com e sem mulching. No cultivo de março a junho/2002, houve maior variabilidade quanto ao comportamento das cultivares avaliadas nos ambientes estudados. Na análise multivariada de agrupamento, a superioridade das cultivares do grupo lisa parece ter sido influenciada pelo número de folhas, tanto para a época 1, quanto para a época 2. Ressalta-se que, apesar das cultivares do grupo americana apresentarem pior desempenho, as mesmas tiveram os maiores valores de massa seca da parte aérea. Quando se tem como objetivo uma maior produção de alface visando massa seca da parte aérea ou massa fresca da parte aérea, deve-se optar por cultivares do grupo americana, que apresentaram as maiores médias para esta característica. As cultivares do grupo crespa apresentaram as maiores médias para volume de plantas.

The effect of plastic mulch and row covers on the growth and physiology of cucumber

To determine the effectiveness of black plastic mulch alone and in combination with row covers, on growth and physiological changes of cucumber plants, 6 treatments were established in a randomised complete block design with 4 replications: bare soil (control); black polyethylene mulch alone (B); B plus a clear cover of perforated polyethylene (BRCP); B plus a white cover of perforated polyethylene (BRWP); B plus an Agribon cover of polypropylene (BRA); and B plus a Kimberly farm row cover (BRK). For the plants grown with mulch or mulch combined with row covers, the dry weight of leaves 50 days after seeding (DAS), and the dry weight of whole plants (at 50 and 110 DAS) were significantly (P&lt;0.05) different from the control. Early yields of treatments B, BRCP, BRWP, BRA and BRK were 2.1, 1.9, 2.6, 1.9 and 2.4 times higher than the control, which yielded 10 t/ha. Total yields were increased by 9.7, 15.4, 19.8, 14.9 and 20 t/ha, over the control which yielded 104 t/ha. Increases in plant dry weight explained the changes in yield. Stomatal conductance may explain in part, the increase in photosynthetic rate, but may not explain yield increase.

Impact of various growing methods on tomato (Lycopersicon esculentum Mill.) yield and sensory quality

The effect of various growing methods of tomato (Lycopersicon esculentum Mill.) cv. Hector on fruit yield and sensory properties was examined. The growing methods used were: bare soil (BS), black plastic mulch (BPM), bare soil with polypropylene row cover (BS + RC) and black plastic mulch with polypropylene row cover (BPM + RC). The yields of all growing methods were reduced during growing season of extreme rainfall. The results show that the use of BPM + RC resulted in the highest total fruit yield (15.93 t ha-1). By using row cover (BS + RC or BPM + RC) it has been observed that marketable yield could be significantly higher than in the BS and the BPM treatments. Plants grown in the BPM and in the BPM + RC yielded larger number of fruits in comparison to plants in the BS or in the BS + RC. The fruit height and diameter were not affected by the treatments. This study also gives a sensory characterisation of various growing methods as an indicator of suitability for growing and marketing of tomatoes. Tomatoes grown in the BPM + RC resulted in the highest total taste intensity.

Earliness and Yield of Tropical Winter Squash Improved by Transplants, Plastic Mulch, and Row Cover

Field studies were conducted in 1998 and 1999 in Massachusetts to assess the effects of transplants, black polyethylene mulch, and polyester spun-bonded row cover on early fruit set and total yield of two squash (Cucurbita moschata Duchesne) cultivars: `C42 × La Segunda' calabaza and `Waltham' butternut. Treatment comparisons included direct-seeded or transplanted squash, with or without black polyethylene mulch, and with or without the addition of a row cover in all combinations. The use of transplants was more effective at stimulating early fruit set and highest total yield than the use of mulch and row cover. The initiation of fruit set using transplants was advanced 9 days relative to direct-seeding. Mulch and row cover treatments significantly advanced early fruit set by 7 and 5 days, respectively, but only in 1998. Yields for both winter squash were 45% higher using transplants compared to direct seeding, 19% higher using mulch compared to bare soil, and 16% higher using row cover compared to no row cover. Total yields were higher for both cultivars in 1999 (warm, dry season) than in 1998 (cool, wet season). Use of transplants with plastic and row cover compared to the use of direct seed with neither plastic nor row cover increased yield of calabaza by 100% in both 1998 and 1999. Only the direct seeded plus plastic plus row cover treatment had yields that were similar to any of the transplanted treatments. Transplant treatments also increased number of fruit per plant and fruit size for both calabaza and butternut.