Unheated Greenhouse Research Articles

EFFECTS OF COVER CROPS ON YIELD AND QUALITY OF ORGANICALLY GROWN GREENHOUSE TOMATOES

This research was conducted in order to determine the effects of cover crops on yield and fruit quality of organic greenhouse tomatoes during spring and autumn growing seasons of 2009 and 2010. The tested cover crops were lupine (Lupinus albus L.), cowpea (Vigna sinensis L.), crimson clover (Trifolium incarnatum L.), scarlet pimpernel (Dichondra repens L.), vetch (Vicia sativa L.) and alfalfa (Medicago sativa L.). They were used as no-till and/or living mulch. In autumn the treatments were (1) lupine (no-till mulch), (2) lupine (living mulch), (3) cowpea, (4) crimson clover, (5) scarlet pimpernel, (6) black PE mulch and (7) control; in the spring season they were (1) lupine, (2) vetch (no-till mulch), (3) vetch (living mulch), (4) alfalfa, (5) scarlet pimpernel (living mulch), (6) black PE mulch and (7) control. Total yield changed between 9.4 and 5.9 kg m-2 in autumn. The highest yield was obtained from lupine (no-till mulch) and followed by cowpea and scarlet pimpernel. In spring growing cycle, yield was between 13.26 and 8.50 kg m-2. Vetch and lupine applied as no-till mulch resulted in the highest yields. The changes in fruit quality parameters excluding total soluble solids were found significant in autumn whereas no significant difference was determined in spring growing season. According to overall results, it was concluded that among the tested cover crops lupine could be appropriate for organic tomato growing in unheated greenhouse conditions.

LOCAL OPTIMIZATION OF THERMAL STORAGE FOR GREENHOUSES: REDUCTION OF ENERGY INPUT AND IMPROVEMENT OF INNER CLIMATE

In temperate regions, such as the Mediterranean basin, there is a diurnal excess of energy nearly every day of the year, which is usually dissipated through natural ventilation. However, since suboptimal nighttime temperatures limit productivity of unheated greenhouses for several months a year, extracting the daytime excess energy and reusing it to heat the greenhouse during the night would increase productivity, or at least reduce energy consumption of greenhouses that are heated. This heat extraction would have the additional advantage of reducing ventilation requirement thereby increasing the scope for carbon dioxide fertilization. To achieve this, the performance of the greenhouse as a solar collector has to be maximized by an efficient heat exchanging and heat buffering system. The aim of this research was to define the optimum combination of heat exchange rate, maximum water flow rate of a heat storage buffer and buffer capacity in a commercial green¬house in the Mediterranean region (Sicily, Italy, 37 °N), the cost function being represented by the dose (duration × intensity) of low temperature events. The green¬house temperature was calculated through a previously validated greenhouse climate simulation model, applied to one-year of real local data. The effect of the buffer on the cost function was first calculated for a range of heat exchange values followed by a cost function evaluation for nodes of a pre-selected grid, each node representing a value-pair for the other two buffer defining parameters. In this paper we analyze the trend of the cost function with respect to each parameter of the buffer and how this is affected by the preset tolerance of low temperatures. Furthermore, we discuss a simple method to find an “optimal” configuration of the buffer. Finally, a combination of 3000 m3 ha-1 buffer capacity, 45 m3 h-1 ha-1 maximum water flow rate and an overall heat transfer coefficient of 5 W m-2 K-1 is selected (heat transfer coefficient is defined per m2 greenhouse floor area).

Usefulness of japanese bunching onion (Allium fistulosum L.) for forcing in greenhouse

The purpose of this work was the evaluation of yielding and the content of some chemical ingredients of Japanese bunching onion yield obtained from forcing in greenhouse conditions. Plants used for forcing were from field cultivation and had the pseudostem trimmed in the autumn of each year (2002, 2003 and 2004) at the height of 2-4 and 8-10 cm. In the spring of the following year (2003, 2004 and 2005) from the middle of March, the plants were forced in a heated greenhouse (temperature 16-20<sup>°</sup>C) and an unheated one (temperature 6-12 <sup>°</sup>C). The whole yield was evaluated when the plants reached the market size for bunching. The weight and height were determined in the plants, as well as the number of laterals and leaves in clusters. In green shoots and the pseudostem, the content of dry weight, total and reducing sugars, L-ascorbic acid, flavonoids and phenolic acids were determined. Very high yield of plants useful for bunching was obtained (average 13.7 kg·m<sup>-2</sup> of area). The plants with a longer pseudostem before forcing yielded better. The conditions of forcing did not have a significant influence on the size of the obtained yield, but the content of L-ascorbic acid and flavonoids was much higher (especially in green shoots) in the plants from forcing in the unheated greenhouse. Lower temperature at the time of forcing was favorable to higher reducing sugar content, especially in the pseudostem. Japanese bunching onion turned out to be useful for forcing for harvest in bunching form.

The effect of the method and time of seedling production on red cabbage (Brassica oleracea L. ssp. oleracea convar. capitata (L) Alef. var. capitata L. f. rubra DC.) yield

This study, conducted in the period 2006-2008, involved an evaluation of yield and commercially useful traits of red cabbage grown from seedlings produced from seeds sown at three different times (the second decade of April, the third decade of April, and the first decade of May). Seedlings were produced in multicell trays in an unheated greenhouse and in a nursery bed from seeds sown at the same time. The experiment included 6 red cabbage cultivars (‘Huzaro F<sub>1</sub>’, ‘Kalibos’, ‘Langedijker Polana’, ‘Rodeo F<sub>1</sub>’, ‘Roxy F<sub>1</sub>’, ‘Zelox F<sub>1</sub>’). After cabbage heads were harvested in the second decade of October (in each year), total and marketable yield as well as head weight and the head shape index were determined. Red cabbage yield was shown to be significantly dependent on the cultivar, time of sowing, and method of seedling production. Among the cultivars studied, the following proved to be the most productive, irrespective of the other experimental factors: ‘Zelox F<sub>1</sub>’ (marketable yield averaged 398.11 kg×100 m<sup>-2</sup>), ‘Roxy F<sub>1</sub>’ (marketable yield averaged 368.82 kg×100 m<sup>-2</sup>), and ‘Rodeo F<sub>1</sub>’ (marketable yield averaged 331.59 kg×100 m<sup>-2</sup>). The cultivar ‘Kalibos’ was characterized by the lowest marketable yield (on average 257.09 kg×100 m<sup>-2</sup>). Delayed sowing (to produce seedlings) by 10 and 20 days, compared to the earliest sowing time, had a significant effect on the reduction in total and marketable yield. Irrespective of the time of sowing, the production of seedlings in multicell trays did not have a significant effect on higher head weight. But the influence of the cultivar was significant - heads of the highest weight were found in the yield of the cultivar ‘Zelox F<sub>1</sub>’ (head weight was on average 1.71 kg). The head shape index was more than 1 and on average it did not exceed 1.35. The cultivar ‘Kalibos’ had the most elongated heads (with a conical shape), while cabbage heads in the cultivar ‘Langedijker Polana’ were closest to the spherical shape.

Growth, yield and fruit quality of three papaya cultivars grown under protected cultivation

Introduction . Papaya is grown mainly under tropical conditions due to its requirement of high temperatures year-round. With modern greenhouse technology and production systems, the Mediterranean countries are now able to produce many tropical crops such as banana and papaya. Such technology has also increased the yield and improved fruit quality in comparison with open field production systems. Materials and methods . Our study was conducted in an unheated greenhouse in the Mediterranean region of Turkey. Three papaya cultivars (‘SS-45’, ‘BH-65’ and ‘Sel-42’) were evaluated for their physical and physicochemical properties and yield. Results . There were no significant differences in chemical properties related to fruit cultivars. Conversely, certain features of the development cycle of these three cultivars varied: BH-65 flowered at only 65.4 cm compared with SS-45 (133.8 cm) and Sel-42 (135.1 cm). Fruit set was improved for Sel-42 (63.7 fruits) compared with SS-45 (49.3 fruits) and BH-65 (31.3 fruits). The corresponding yields for Sel-42, SS-45 and BH-65 were (28.3, 21.3 and 7.8) kg per plant, respectively. The Sel-42 cultivar presented the largest fruits (weight, 460.0 g; width, 11.7 cm; length, 16.7 cm), closely followed by those of SS-45 (433.3 g, 11.3 cm and 15.3 cm, respectively). In contrast, the cultivar BH-65 produced the smallest fruits (weight, 250.0 g; width, 9.7 cm; length, 13.3 cm). The physical and chemical characteristics did not vary among the cultivars. Conclusion . Our results allow us to recommend the cultivars Sel-42 and SS-45 for greenhouse cultivation under a Mediterranean climate in Turkey.

A CFD greenhouse night-time condensation model

A computational fluid dynamics (CFD) model for simulating greenhouse night-time climate and condensation is presented. The model was applied to a four-span plastic covered greenhouse. Film condensation was simulated by applying a user defined function (UDF) added to the commercial CFD package. The CFD model was verified by comparing CFD predictions with experimental measurements. The effect of cover temperature on greenhouse humidity was then determined by the CFD model and compared to experimental results. Root mean square values for the differences between the CFD and experimental values of internal temperature and humidity showed there was good agreement between. The results showed the importance of heat transfer losses by radiation, particularly for low values of soil heat flux (SHF). They also showed the roof was the coolest surface in the greenhouse, and therefore the sink for the water vapour produced by the crop. For each configuration (SHF 10, 25, 50 and 100 W m−2 and equivalent sky temperature 263 K, 273 K and 276 K), the condensation rate curves and relative humidity (RH) evolution are presented. It was observed that all the condensation rate curves had the same characteristic shape and could be represented by a single logistic function. The response of the CFD model to a step-change in the water vapour source (night-time transpiration from the crop) was then analysed. It was observed that the model predicted the same steady-state temperature, RH and condensation rate independent of the time when the water vapour source was enabled. The CFD condensation model is intended to be used for the design of strategies for humidity control, particularly in unheated greenhouses.

Effect of nocturnal ventilation on the occurrence of Botrytis cinerea in Mediterranean unheated tomato greenhouses

Botrytis cinerea is the causal agent of grey mould disease which is one of the most important diseases affecting tomato crops in unheated greenhouses. Nocturnal ventilation is a technique that can be used to reduce relative humidity inside unheated greenhouses. The main objectives of this research were to investigate the effect of ventilation management on the environmental conditions and on the Disease Severity, to develop and validate a model which could predict Disease Severity and to present a warning system. Experiments were conducted in two plastic greenhouses. Two natural ventilation treatments were randomly assigned to the greenhouses. One was nocturnal ventilation (NV), with the vents open during the day and night, while the other was classical ventilation (CV), in which the vents were open during the day and closed during the night. A tomato crop was grown directly in the soil between the end of February and the end of July during two crop seasons. Climatic data were measured with three meteorological stations, averaged and recorded on an hourly basis. The number of diseased leaflets were counted and removed from the greenhouse. In the NV greenhouse a significant reduction of air humidity and disease appearance was observed. A warning system was developed and can be a useful tool for helping to decide on appropriate actions and the correct timing to avoid conditions that favour disease development. For a more practical application, disease risk levels were defined as a function of the duration of periods with RH > 90%.

Effects of chlormequat chloride and different rates of prohexadione-calcium on seedling growth, flowering, fruit development and yield of tomato

The aim of the study was to determine the effects of chlormequat chloride and different rates of prohexadione-calcium on seedling growth, flowering and fruit development and yield characteristics of tomato under conventionally poor growing conditions in an unheated greenhouse in Tekirdag, Turkey (40°59' N, 27°29' E). The effects of medium drench and spray applications of chlormequat chloride (2000 mg l -1 ) and different rates of prohexadione-calcium [(Regalis ® )(50, 100, 200, 250, 300, 100 × 2, 125 × 2 and 150 × 2 mg l -1 )] were evaluated. Chlormequat chloride and prohexadione-calcium effected seedling height, seedling diameter, number of leaves, chlorophyll, total and early yields, fruit diameter, percentage of fruits falling into the weight classes and flowering, and fruit development of tomato. In exception of 4 of 16 treatments, prohexadione-calcium, as well as chlormequat chloride, reduced seedling height related to control. The highest total yield was observed with chlormequat chloride and medium drench and spray applications of 100 and 300 mg l -1 and spray application of 100 × 2 mg l -1 prohexadione-calcium (pro-Ca). The lowest average fruit weight was from 150 × 2 mg l -1 and control plots. Fruit diameters were larger with the most of the pro-Ca rates in comparison to the control plants. In some pro-Ca treatments, flowers in the first florescences remained either at anthesis or fruit set stage throughout the growing period. Nevertheless, flower and fruit developments were normal in the 2nd, 3rd and 4th trusses in these treatments. Key words: Prohexadione-calcium, chlormequat chloride, seedling height, flowering, yield, tomato.

Modelling Botrytis cinerea spore exchanges and production in unheated greenhouses

SUMMARY In order to devise optimal and sustainable strategies to protect greenhouse grown crops against Botrytis cinerea, production of spores inside the greenhouses and exchanges with the outside need to be monitored. Such knowledge could be used for adequate timing of measures aimed at limiting the entry of exogenous inoculum and others aimed at limiting the multiplication of the endogenous inoculum. In an earlier study, a model based on spore mass balance was developed to estimate the production of B. cinerea spores inside a greenhouse and the number of spores entering and leaving the greenhouse. This model was successfully used in a heated glasshouse. As much of the tomato production also occurs in more open and less controlled conditions, the present study aimed at testing the model in non heated plastic greenhouses (tunnels) where environmental parameters known to influence spore exchanges and production differ from a glasshouse setting. When diseased plants were present in the tunnel, the production of spores over 24 h estimated by the model was equivalent to 5 to 10% of the maximum potential amount present on the plants, which was coherent with the amount of spores likely to be released by the action of wind on sporulating lesions. Exchange of spores was toward the outside. When the tunnel was empty or contained disease-free plants, fewer spores were exchanged and the spore movement was globally from the outside toward the inside of the tunnel.

How plastic mulches affect the thermal and radiative microclimate in an unheated low-cost greenhouse

Suboptimal regimes of air and soil temperature usually occur under unheated greenhouses during winter crop cycles. This work analyses the effects of three soil surface treatments (no plastic mulch, NM; transparent mulch, TM, and black mulch, BM) on the air-soil heat exchanges and the resulting soil and aerial microclimate. Experiments were conducted in unheated greenhouse compartments located in an area of mild winter climate (South-East Spain) during autumn and winter periods. In all treatments, the soil consisted of an artificial layer of 0.10 m gravel-sand material placed above a 0.3 m layer of imported loamy soil. When vents were closed, soil heat flux, ground net radiation and both air and root-zone temperature were higher in BM than in TM, while NM presented intermediate performances between BM and TM. When vents were open, heat storage and soil warming were substantially reduced with respect to unventilated conditions. This reduction was greater in BM, and so the advantages of BM with respect to the other treatments were only marginal under ventilated conditions. The main conclusions were: (i) The combination of black mulch + greenhouse appears to be a simple and low-cost passive heating system that can be recommended for the early stages of crop cycles starting at the end of autumn or in winter, when canopy leaf area index is small and most of the soil surface is free of vegetation; and (ii) ventilation had a negative effect on the benefits of mulching, implying that greenhouse ventilation management should reflect a compromise between maximizing greenhouse heat storage and fulfilling ventilation requirements for suitable crop growth.

Cold‐Induced Biochemical and Molecular Changes in Alfalfa Populations Selectively Improved for Freezing Tolerance

Synthetic populations obtained after successive cycles of recurrent selection for superior tolerance to freezing were used to probe the molecular bases of superior adaptation to cold in alfalfa (Medicago sativa L.). The initial genetic backgrounds and populations derived from the cultivars Apica and Evolution were assessed for their freezing tolerance and cold‐induced molecular changes using plants acclimated to natural hardening conditions in an unheated greenhouse. Significant increase in freezing tolerance in response to recurrent selection was confirmed by the determination of the lethal temperature for 50% of the plants (LT50). Improvement of freezing tolerance was associated with differences in cold‐induced molecular changes. Starch reserves in crowns progressively declined during fall hardening with a more extensive mobilization observed in advanced cycles of selection. Concentrations of cryoprotective sugars and of the amino acids proline, asparagine, and arginine increased during fall hardening and were significantly higher in recurrently selected populations than in the initial backgrounds. Transcript levels of two cold‐regulated (COR) genes, cas15 and GaS, were strongly up‐regulated during fall hardening and significantly increased in response to selection mostly in the Apica background. Our results provide evidence that recurrent selection for superior freezing tolerance in alfalfa induces marked changes in traits associated with the cold acclimation process.

Effects of nutrition systems and irrigation programs on tomato in soilless culture

Abstract A research has been carried out to determine the effects of nutrition systems and irrigation programs on soilless grown tomato plants under polyethylene covered unheated greenhouse conditions. Two nutrition systems (open and closed) and three irrigation programs (high, medium and low) based on integrated indoor solar radiation triggering thresholds (1 MJ m −2 [0.4 mm], 2 MJ m −2 [0.8 mm] and 4 MJ m −2 [1.6 mm]) in both nutrition systems have been tested. Applied and discharged nutrient solution, evapotranspiration, total and marketable yield have been measured and water use efficiency has been calculated. The highest total yield has been obtained from the open system with respectively 11% and 7.2% increases in autumn and spring. Applied nutrient solution volume and seasonal ET have been modified between 47.8–180.4 l plant −1 and 41.7–145.5 l plant −1 respectively during both growing seasons. As average of two growing seasons, respectively 826.5 and 330.6 m 3 ha −1 nutrient solutions have been discharged from the greenhouse in the open and closed systems. WUE of treatments varied between 33–55 kg m −3 in autumn and 26–35 kg m −3 in spring. Highest WUE values have been determined in 4 MJ m −2 and in the closed system in both growing seasons. Results showed that the closed system and infrequent irrigations increased water use efficiency while decreasing yield and discharged nutrient solution.

The effects of different sowing time practices on Vitamin C and mineral material content for rocket (Eruca vesicaria subsp. sativa (Mill))

Salad rocket largely differs in composition and content for antioxidants such as Vitamin C together with a significant variability of bioactive compounds. Rocket encloses the highest Vitamin C content among the Brassicaceae vegetables used for salad. The content of Vitamin C and minerals in plants is affected by seasonal factors such as sowing time and the date of harvesting. The existence of Vitamin C and mineral materials in the content of green leaved vegetables are subject to different factors. The main factors are light and temperature. The aim of this study is to determine the values of antioxidant worthy Vitamin C and mineral material for rocket on different sowing times – fall and spring – that have different light and temperature conditions. Experiments were carried out in an unheated greenhouse in fall and spring growing period in Corlu, Turkey (41°11'N, 27°49'E). Results indicated that the rocket grown in fall sowing time has the maximum Vitamin C content as 57.41 mg 100 g – 1. Moreover, N, P and K values in fall sowing time are at the highest values as 3.69, 0.30 and 3.02% respectively. For rocket; Ca, Fe, Cu, and Zn contents reached at the highest values in fall sowing time; however, spring sowing time offered uppermost values for Mg and Mn contents in the research. In addition to its relatively short cultivating period, rocket has an easy growing vegetable. With its content of Vitamin C and mineral materials, it can be a good alternative crop for fall growing periods in an unheated greenhouse as well. Key words: Rocket (Eruca vesicaria subsp.sativa (Mill)), different sowing time, vitamin C, mineral content.

Frost Dehardening and Rehardening of Hydrangea macrophylla Stems and Buds

Hydrangea macrophylla is a popular and commercially important flowering shrub, but frost injury of buds and current-year shoots is a common problem in some of its cultivars. As a result of climate warming, temperate winters are becoming progressively milder, and temperature patterns are becoming increasingly irregular with an increased frequency of warm spells. Warm spells may induce premature dehardening, increasing the risk of subsequent freezing injuries. This study investigated cold-hardiness of stems and buds of Hydrangea macrophylla ssp. macrophylla (Thunb.) Ser. ‘Alma’ during dehardening in response to simulated warm spells and subsequent rehardening in January and early March. Plants were acclimated in the field and dehardened in the greenhouse at controlled warm temperatures for various durations. Dehardened plants were rehardened for up to 12 days in an unheated greenhouse (January) or in the field (March). Buds of H. macrophylla were slightly less cold-hardy than stems. In both stems and buds, the dehardening resistance and the rate of dehardening were influenced by temperature, but buds appeared to be less resistant to dehardening and dehardened faster than stems. In stems, dehardening proceeded faster in March than in January, and the capacity of the stems to reharden seemed reduced, indicating that both dehardening and rehardening were influenced by the progression of winter. Results of this study indicate that buds of H. macrophylla are more sensitive to frost injury than stems and the vulnerability of stems to frost injuries, caused by an unstable temperature regime, changes during the winter season.

Survival of cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae), through winter cleanups of commercial vegetable greenhouses: Implications for insecticide resistance management

Cabbage looper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), is a highly migratory and destructive pest of various crops in North America. Its infestations in vegetable greenhouses in western Canada are generally attributed to annual immigrations from southern overwintering areas, but whether it survives overwinter in western Canada is uncertain. Bioinsecticides based on Bacillus thuringiensis ( Bt) toxins are commonly used in southwestern British Columbia where some T. ni populations have developed strong resistance to Bt-insecticides. In this study, overwintering success of T. ni populations was monitored outside and inside three commercial greenhouses in British Columbia. In both years, T. ni pupae placed outside greenhouses did not survive although pupae placed inside the greenhouses survived the unheated cleanup period and exposure to organophosphate insecticides commonly used in the cleanup procedure in the greenhouses. During the cleanup period, no moths were caught inside the unheated greenhouses, but once the heating was restored for the new growing season, adults were captured in pheromone traps. No developmental stages of T. ni were detected on nursery seedlings and visual monitoring of transplants at the beginning of the season found no signs of previous feeding damage. This strongly suggests that T. ni were not introduced with the seedlings. Our findings are important for understanding the potential risks of inadequate winter cleanup and the potential carryover of resistance to Bt-insecticides in populations from one season to the next that could complicate pest management.

LEAF AND BUD TEMPERATURES OF SOUTHERN HIGHBUSH BLUEBERRIES (VACCINIUM CORYMBOSUM) INSIDE HIGH TUNNELS

A high tunnel is a passively heated and cooled plastic-covered greenhouse used for season extension and crop protection for a variety of horticultural crops, including southern highbush blueberry (Vaccinium corymbosum L.). Frost protection remains a major challenge for early-season blueberry production, due to poor heat retention by high tunnels. Understanding the energy balance of high tunnels is essential for predicting night-time minimum temperatures and implementing frost protection strategies. We determined the effects of high tunnels on air, leaf, and bud temperatures of southern highbush blueberry. Impacts of frost blankets (one frost protection strategy) on temperatures were also explored. High tunnels quickly warmed during the day but cooled to ambient or below ambient air temperature at night, particularly during clear days and nights. Leaf and bud temperatures in high tunnels were higher than those of outdoor plants during the day but lower during night. The presence of a frost blanket reduced night-time radiative cooling of leaves and buds and allowed their temperatures to stay closer to ambient conditions inside of high tunnels. Lack of night-time heat retention in high tunnels was likely due to the properties of the polyethylene greenhouse cover, lack of ventilation, and large surface area to volume ratio of the high tunnels. INTRODUCTION A high tunnel is an unheated plastic greenhouse that is passively ventilated and can be erected over large areas (Lamont, 2003). They lend themselves well to organic horticultural practices and are becoming indispensable components of many organic farms. Blueberries are an economically significant crop for Georgia and production of out-of-season organic blueberries in high tunnels could be a financially lucrative endeavor for Georgia’s growers. The research reported here was part of a larger project to examine the feasibility of production of early organic southern highbush blueberries inside of high tunnels in Georgia (USA). The main goal of the overall research project was to discover the ideal date of closing high tunnels to achieve both early and high blueberry yield. In the first year of this project, we found that increased daily maximum air temperatures inside high tunnels facilitated early flowering, fruiting, and onset of vegetative growth (Ogden et al., 2007). The major limitation of the high tunnels was their inability to retain heat during cold nights. Night-time minimum air temperatures inside the high tunnels were equal to or lower than outside air temperatures (Ogden and van Iersel, 2008). Likewise, Montero et al. (2005) reported that the air in unheated greenhouses was about 2.5°C cooler than the outside air. The lack of frost protection provided by the high tunnels necessitated the use of propane heaters on nights with minimum temperature below 0°C to protect the developing, freeze sensitive flowers and buds. The research reported here was conducted during the second year of this project. In an effort to reduce fuel costs, we also experimented with frost blankets on nights with predicted lows of 0 to -1°C during the

FARKLI EKİM ZAMANI VE UYGULAMALARIN CENSİYAN (Gentiana Lutea Subs. Symphyandra) TOHUMLARININ ÇIKIŞ GÜCÜ ÜZERİNE ETKİLERİNİN BELİRLENMESİ

This study was carried out at Yalova Ataturk Central Horticultural Research Institute between 2009-2010, in order to determine potential of seed germination of yellow gentian (Gentiana lutea subs.symphyandra), a rarely disseminated and endangered species in Turkey due to collection from the nature. In this study, the emergence rate of seeds treated different pretreatments were determined at unheated greenhouse conditions at different dates. Moreover the emergence rate of seeds treated with stratification at +1 oC in different periods and different sowing times were determined at outdoor. At the end of the study, seeds treated with stratification at +1 oC in different periods at unheated greenhouse and stratification at +1 oC from seed harvest until 1-15 January at outdoor showed the best emergence rate.

Opportunities for Growing Tribulus Terrestris L. as Semi-Culture

ABSTRACTSome opportunities for the use of Tribulus terrestris L. as a semi-culture were investigated in the field of the Maritsa Vegetable Crops Research Institute, Plovdiv, during the period 2009–2010. The trials were carried out in the open field. Tribulus terrestris L. seedlings were grown in an unheated greenhouse from the end of March until the end of April. The plants were transplanted in the open field at the beginning of May. Two schemes of growing were applied in the open field on a high bed in one and two rows, with 1 m distance between the plants. Two drip irrigation regimes were used: 77.5 m3/ha and 310 m3/ha for two rows, 38.7 m3/ha and 77.5 m3/ha for one row.It was established that growing on high bed in two rows, with 310 m3/ha irrigation rate was more suitable for growing Tribulus terrestris L. in the open field.

Hoophouse Contributions to Economic Viability: Nine Michigan Case Studies

Relatively low-cost season extension structures have the potential to contribute to farm economic viability in temperate climates by providing a means to continue sales beyond the limits of outdoor-only field production. These structures, commonly called hoophouses, high tunnels, passive solar greenhouses, or unheated greenhouses, allow for the extension of heat-tolerant (warm season) crops on both ends of the production time frame and at winter harvesting of cold-tolerant (cool season) crops. In this study, results are presented from a multiyear investigation into the economic impacts of year-round production and harvesting, with a focus on profitability of the structure and crop production as a whole. The results of case studies from nine Michigan farms reveal a very broad range of outcomes across farms in construction time, labor allocation and returns, and gross and net revenue. The economic implications of farmer use, including projected investment payback time, are discussed.

Experimental study of the energy balance of unheated greenhouse under hot and arid climates: Study for the night period of winter season

In regions with warm and hot climates as is the case of several countries of the Mediterranean basin, it is interesting to study the energy balance inside a greenhouse and to quantify the heat transfers along the building components (roof, walls and ground) in winter and during night time. The present experimental work was conducted in an unheated glasshouse without crop in the region of Batna, Algeria. Three types of measurements were done from January to March: the first one is at a cloudy night; the second one at a windy night and the third one at a cloudless night. The results indicate that the greenhouse ground is considered as a significant heat source which can compensate the energy losses through the walls especially during a night preceded by a significant diurnal insulation. In addition, the convection heat transfer coefficients inside and outside the greenhouse were estimated and analysed. A good agreement with the models reported in the literature was found.