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Gerben J. Messelink - One of the best experts on this subject based on the ideXlab platform.
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Provision of astigmatid mites as supplementary food increases the density of the predatory mite Amblyseius swirskii in Greenhouse Crops, but does not support the omnivorous pest, western flower thrips
BioControl, 2021Co-Authors: Fatemeh Pirayeshfar, Seyed Ali Safavi, Hamid Reza Sarraf Moayeri, Gerben J. MesselinkAbstract:Astigmatid mites can be used as prey for mass rearing of phytoseiid predators, but also as a supplemental food source to support predator populations in Crops. Here we evaluated the potential of six species of astigmatid mites (living or frozen) as alternative food for the predatory mite Amblyseius swirskii Athias-Henriot in Greenhouse Crops. All prey mites tested were suitable for predator oviposition. In general, oviposition was greater when prey mites were reared on dog food with yeast than when they were reared on wheat bran with yeast. Amongst prey items provided as frozen diet, larvae of Thyreophagus entomophagus (Laboulbene), Acarus siro L. and Lepidoglyphus destructor (Schrank) that had been reared on dog food with yeast, resulted in the highest oviposition rates of A. swirskii . T. entomophagus larvae as frozen diet resulted in the shortest preimaginal developmental time of A. swirskii . On chrysanthemum plants, we found that the greatest increase in predator density occurred when living mites of T. entomophagous were used as a food source. This increase was greater than when predators were fed cattail pollen, a commonly used supplemental food. Effects on predators of providing living A. siro and L. destructor , or frozen larvae of T. entomophagous as food, were comparable with provision of pollen. Use of supplemental food in Crops can be a risk if it is also consumed by omnivorous pests such as western flower thrips, Frankliniella occidentalis Pergande. However, we showed that both frozen and living mites of T. entomophagous were unsuitable for thrips oviposition. Hence, we believe that provision of prey mite species increases A. swirskii density, supporting biological control of thrips and other pests in Greenhouse Crops.
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New opportunities for the integration of microorganisms into biological pest control systems in Greenhouse Crops
Journal of Pest Science, 2016Co-Authors: Francisco González, Żaneta Fiedler, Einat Zchori-fein, Mihaelamonica Dinu, Cezary Tkaczuk, Stefan Vidal, Gerben J. MesselinkAbstract:Biological pest control with mass-produced arthropod natural enemies is well developed in Greenhouse Crops and has often resulted in the evolution of complex ecosystems with persistent populations of multiple arthropod natural enemy species. However, there are cases where arthropod natural enemies are either not effective enough, not available, or their use is rather costly. For these reasons, biological control based on microorganisms, also referred to as ‘microbials’, represents a complementary strategy for further development. Although commercially available microbials have been around for quite some time, research on and the applied use of combinations of arthropod natural enemies and microbials have remained relatively under explored. Here, we review current uses of entomopathogenic fungi, bacteria and viruses, and their possible direct and indirect effects on arthropod natural enemies in European Greenhouses. We discuss how microbials might be combined with arthropod natural enemies in the light of new methodologies and technologies such as conservation biological control, Greenhouse climate management, and formulation and delivery. Furthermore, we explore the possibilities of using other microorganisms for biological control, such as endophytes, and the need to understand the effect of insect-associated microorganisms, or symbionts, on the success of biological control. Finally, we suggest future research directions to optimize the combined use of microbials and arthropod natural enemies in Greenhouse production.
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Approaches to conserving natural enemy populations in Greenhouse Crops: current methods and future prospects
BioControl, 2014Co-Authors: Gerben J. Messelink, Oscar Alomar, Jude Bennison, Barbara L. Ingegno, Luciana Tavella, Les Shipp, Eric Palevsky, Felix L. WäckersAbstract:Biological pest control in Greenhouse Crops is usually based on periodical releases of mass-produced natural enemies, and this method has been successfully applied for decades. However, in some cases there are shortcomings in pest control efficacy, which often can be attributed to the poor establishment of natural enemies. Their establishment and population numbers can be enhanced by providing additional resources, such as alternative food, prey, hosts, oviposition sites or shelters. Furthermore, natural enemy efficacy can be enhanced by using volatiles, adapting the Greenhouse climate, avoiding pesticide side-effects and minimizing disrupting food web complexities. The special case of high value Crops in a protected Greenhouse environment offers tremendous opportunities to design and manage the system in ways that increase crop resilience to pest infestations. While we have outlined opportunities and tools to develop such systems, this review also identifies knowledge gaps, where additional research is needed to optimize these tools.
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generalist predators food web complexities and biological pest control in Greenhouse Crops
Integrated Pest Management and Pest Control - Current and Future Tactics, 2012Co-Authors: Gerben J. Messelink, Maurice W Sabelis, Arne JanssenAbstract:Biologische bestrijding van plagen in kassen was lange tijd voornamelijk gericht op specialistische natuurlijke vijanden die sterk zijn aangepast aan hun prooi. Gerben Messelink onderzocht de rol van generalistische predatoren bij de bestrijding van meerdere plagen in de teelt van vruchtgroenten in kassen. Uit zijn resultaten blijkt dat spintmijten en witte vliegen - twee wereldwijde plagen - op een komkommergewas veel beter worden bestreden met generalistische roofmijten wanneer er ook tripsen (een ander belangrijk plaaginsect) aanwezig waren. Dit komt vooral doordat de roofmijten zich op een dieet van verschillende prooien sneller ontwikkelen. Hierdoor worden er snel hoge predatordichtheden bereikt. Messelink vond een vergelijkbaar mechanisme bij de bestrijding van plagen in paprika: roofwantsen gaven een zeer goede bestrijding van bladluis in de aanwezigheid van tripsen. Messelink verwacht dat generalistische predatoren in toenemende mate gebruikt zullen worden voor biologische plaagbestrijding in kassen, omdat de predatoren profiteren van een gemengd dieet van verschillende plagen en de plaagbestrijding op die manier makkelijker maakt.
Santiago Bonachela - One of the best experts on this subject based on the ideXlab platform.
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Regulated deficit irrigation in green bean and watermelon Greenhouse Crops
Scientia Horticulturae, 2009Co-Authors: Alicia Maria Gonzalez, Santiago Bonachela, María Dolores FernándezAbstract:Abstract Mediterranean Greenhouse growers of watermelon and green bean Crops tend to reduce slightly the soil water availability during the flowering phase to enhance the fruit number and yield, but without measuring the soil or the plant water status. This deficit irrigation strategy (RDI) was studied on two representative growth cycles of green bean and one of watermelon. In each case, a well-watered crop acted as control. In the three well-watered vegetable Crops, soil water matric potential (SMP) values were between −20 and −30 kPa throughout most of the respective growth cycles. These values avoid water deficits in Mediterranean Greenhouse vegetable Crops. The watermelon under RDI presented similar SMP to the well-watered crop, except during the flowering period when it reached values of −50 to −60 kPa, which are similar to, or slightly lower than, those recommended to prevent water deficits for cucurbitaceae Crops. The autumn–winter and spring cycles of green bean under RDI presented progressively lower SMP values from the vegetative phase to the first fruit setting than the well-watered Crops, reaching minimum SMP values of around −55 kPa for the autumn–winter cycle and of −75 kPa for the spring one. These minimum SMP values are similar for the autumn–winter cycle and lower for the spring cycle than those recommended to avoid water deficits in green bean Crops grown in medium-fine textured soils. Overall, mild water deficits during flowering of watermelon and green bean Crops grown in Mediterranean Greenhouses did not improve the final fruit number or yield. In the two spring cycles (watermelon and green bean) the RDI strategy reduced the aboveground biomass and yield, whereas in the autumn–winter green bean cycle the RDI strategy reduced the vegetative biomass but did not affect yield. SMP threshold values can, however, be used by growers as a tool for controlling the equilibrium between the vegetative and reproductive growth of Greenhouse soil-grown Crops.
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analysis of on farm irrigation performance in mediterranean Greenhouses
Agricultural Water Management, 2007Co-Authors: M. D. Fernández, A M Gonzalez, J Carreno, C Perez, Santiago BonachelaAbstract:Abstract A comprehensive irrigation assessment was conducted using on-farm water use information and simulated crop water requirements in a Mediterranean Greenhouse area, mainly dedicated to horticultural Crops, located on the Almeria coast. The mean irrigation water supply (IWS) for the main Greenhouse crop cycles was 228 mm and ranged from 158 mm (autumn green bean) to 362 mm (autumn–spring sweet pepper). Besides, the mean AIWS value for the main crop rotations was 444 mm and ranged between 363 mm for autumn–spring sweet pepper and 502 mm for autumn–winter pepper and spring melon. Mean relative irrigation supply (RIS) values were close to 1 for most Greenhouse vegetable Crops, indicating that, on average, the irrigation supply matched the maximum water requirements of these Crops. By contrast, the mean RIS value of autumn–winter cucumber was 1.6, indicating that, on average, the irrigation supply clearly exceeded the calculated optima. However, for most Crops, the high CV values observed for RIS and the analysis of the RIS dynamics throughout the cycles indicate that there are Greenhouse Crops and crop cycle periods for which the IWS clearly does not match the crop water requirements. Greenhouse irrigation water use in the Almeria coastal region can, therefore, be improved. Mean irrigation water use efficiency (IWUE) values for Greenhouse horticultural Crops ranged from 15.3 kg m −3 (autumn–winter green bean) to 35.6 kg m −3 (spring watermelon). They were, in general, higher than those found when these Crops were grown outdoors in similar climatic regions. Water productivity (WP) varied from 7.8 to 15.9 € m −3 and were highest for green bean Crops. WP values of Greenhouse Crops were generally much higher than those found in other irrigation districts around the world, including Mediterranean areas, due to the low IWS and, especially, to the high value of the vegetable Crops grown off-season.
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irrigation scheduling of plastic Greenhouse vegetable Crops based on historical weather data
Irrigation Science, 2006Co-Authors: Santiago Bonachela, Alicia Maria Gonzalez, M. D. FernándezAbstract:Irrigation scheduling based on the daily historical crop evapotranspiration (ETh) data was theoretically and experimentally assessed for the major soil-grown Greenhouse horticultural Crops on the Almeria coast in order to improve irrigation efficiency. Overall, the simulated seasonal ETh values for different crop cycles from 41 Greenhouses were not significantly different from the corresponding values of real-time crop evapotranspiration (ETc). Additionally, for the main Greenhouse Crops on the Almeria coast, the simulated values of the maximum cumulative soil water deficit in each of the 15 consecutive growth cycles (1988–2002) were determined using simple soil-water balances comparing daily ETh and ETc values to schedule irrigation. In most cases, no soil-water deficits affecting Greenhouse crop productivity were detected, but the few cases found led us to also assess experimentally the use of ETh for irrigation scheduling of Greenhouse horticultural Crops. The response of five Greenhouse Crops to water applications scheduled with daily estimates of ETh and ETc was evaluated in a typical enarenado soil. In tomato, fruit yield did not differ statistically between irrigation treatments, but the spring green bean irrigated using the ETh data presented lower yield than that irrigated using the ETc data. In the remaining experiments, the irrigation-management method based on ETh data was modified to consider the standard deviation of the inter-annual Greenhouse reference ET. No differences between irrigation treatments were found for productivity of pepper, zucchini and melon Crops.
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evapotranspiration of horticultural Crops in an unheated plastic Greenhouse
Agricultural Water Management, 2005Co-Authors: Francisco Orgaz, Santiago Bonachela, M. Gallardo, M. D. Fernández, Elias FereresAbstract:Abstract Large unheated Greenhouse areas are located in the coastal lands of the Mediterranean Basin, based on low-cost structures covered with plastic. Water is a scarce resource in these areas and therefore it is necessary to optimise irrigation practice by applying the crop water needs, thus avoiding waste. This work was undertaken to determine the water requirements of four major horticultural Crops grown in an unheated plastic Greenhouse located in Almeria, Spain. Drainage lysimeters were used to determine the seasonal evapotranspiration (ET) of four Crops (melon, green beans, watermelon and pepper), which ranged from 170 to 371 mm and it was associated with the reference ET (ET 0 ). Compared to irrigated Crops outdoors, the seasonal ET of the Greenhouse horticultural Crops is relatively low due to the lower evaporative demand inside the Greenhouse and to a further reduction in solar radiation transmission by whitening in late spring and summer. Additionally, off-season Greenhouse Crops are grown during low evaporative demand periods, thus the low water requirements. Crop coefficient ( K c ) curves were obtained for the four Crops under different conditions. The K c values varied with the crop, stage of development, and with management practices. Measured peak K c values for Crops, which were not vertically supported (melon and watermelon) were between 1 and 1.1, similar to the measured values for the same Crops under field conditions. By contrast, peak K c values for vertically supported (VS) Crops (melon, green bean and sweet pepper) varied between 1.3 and 1.4, which are higher than those reported for outdoors. The tall and open canopy structures of the VS Greenhouse Crops, their high leaf area indices, along with the high proportion of diffuse radiation inside the Greenhouse, allowed for more uniform light penetration within the canopies and ET rates in those Crops higher than those of the short, non-supported Crops. Management and climatic conditions combined to define an unusual K c curve for sweet pepper. The crop is transplanted in late summer and reaches the peak K c in early winter. Because of the low temperatures, K c decreased thereafter down to about 1.0, until climatic conditions inside the Greenhouse improved. From late winter to the end of the season, K c was either stable or increased steadily. A simple K c model based on thermal time for Greenhouse Crops with and without pruning, was proposed and validated. The model gave accurate estimates of measured K c values for melon and pepper.
Patrick De Clercq - One of the best experts on this subject based on the ideXlab platform.
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intraguild interactions between the mealybug predators cryptolaemus montrouzieri and chrysoperla carnea
Insects, 2021Co-Authors: Laura Golsteyn, Hana Mertens, Joachim Audenaert, Ruth Verhoeven, Bruno Gobin, Patrick De ClercqAbstract:The ladybird Cryptolaemus montrouzieri and the green lacewing Chrysoperla carnea have shown potential for use in augmentative biological control of mealybug pests in Greenhouse Crops. In the context of combining these predators within an integrated pest management system, the risk of negative intraguild interactions between both predators was evaluated in a laboratory setting. Different life stages of either predator were confronted in petri dish arenas containing a Ficus benjamina leaf, and after 24 h the incidence and direction of intraguild predation (IGP) was recorded for each combination. The effect of adding Planococcus citri nymphs or Ephestia kuehniella eggs as extraguild prey on the level of IGP was also studied. IGP was frequently observed between the two predator species and was asymmetrical in favour of C. carnea in most cases. The presence of extraguild prey reduced the number of IGP events between the predators to a similar extent. The relevance of the observed intraguild interactions for the combined use of these predators in protected cultivation is discussed.
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establishment of amblyseius swirskii in Greenhouse Crops using food supplements
Systematic & Applied Acarology, 2016Co-Authors: Dominiek Vangansbeke, Joachim Audenaert, Bruno Gobin, Duc Tung Nguyen, Luc Tirry, Patrick De ClercqAbstract:Abstract Food supplementation is an emerging strategy to improve the establishment and resilience of generalist predators in Greenhouse Crops. This study was conducted to assess the pre-establishment of the generalist predatory mite Amblyseius swirskii Athias-Henriot (Phytoseiidae) on two ornamental Greenhouse Crops, chrysanthemum and ivy. In the first Greenhouse trial, we compared two commercial products consisting of Typha angustifolia pollen and decapsulated brine shrimp cysts (Artemia spp.), respectively, with a powdered artificial diet (AD) as food supplements for the predator on chrysanthemum plants at a constant temperature regime of 25°C at a 16:8 h (L:D) photoperiod. A population of A. swirskii established well when T. angustifolia pollen or the artificial diet were applied, but did not when the Artemia product was used as a supplement. A second trial on ivy plants was conducted at two temperature regimes (a constant 25°C and an alternating temperature regime of 30°C/15°C, both at a 16:8 h (L:D) ...
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establishment of amblyseius swirskii in Greenhouse Crops using food supplements
Systematic & Applied Acarology, 2016Co-Authors: Dominiek Vangansbeke, Joachim Audenaert, Bruno Gobin, Duc Tung Nguyen, Luc Tirry, Patrick De ClercqAbstract:Food supplementation is an emerging strategy to improve the establishment and resilience of generalist predators in Greenhouse Crops. This study was conducted to assess the pre-establishment of the generalist predatory mite Amblyseius swirskii Athias-Henriot (Phytoseiidae) on two ornamental Greenhouse Crops, chrysanthemum and ivy. In the first Greenhouse trial, we compared two commercial products consisting of Typha angustifolia pollen and decapsulated brine shrimp cysts (Artemia spp.), respectively, with a powdered artificial diet (AD) as food supplements for the predator on chrysanthemum plants at a constant temperature regime of 25°C at a 16:8 h (L:D) photoperiod. A population of A. swirskii established well when T. angustifolia pollen or the artificial diet were applied, but did not when the Artemia product was used as a supplement. A second trial on ivy plants was conducted at two temperature regimes (a constant 25°C and an alternating temperature regime of 30°C/15°C, both at a 16:8 h (L:D) photoperiod), comparing T. angustifolia pollen, the artificial diet and a non-commercial strain of Artemia franciscana cysts as food supplements. At the constant temperature regime, all three food sources allowed the establishment of A. swirskii. At the alternating temperature regime, however, T. angustifolia pollen and the AD but not A. franciscana cysts allowed a population of the predator to establish. Failure of establishment on the latter food supplement was attributed to dehydration effects under low humidity conditions in the Greenhouse associated with the higher daytime temperatures at the alternating temperature regime. In conclusion, this study demonstrated the potential of T. angustifolia pollen and an artificial diet as a food supplement to support a population of A. swirskii in different ornamental Crops.
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supplemental food for amblyseius swirskii in the control of thrips feeding friend or foe
Pest Management Science, 2016Co-Authors: Dominiek Vangansbeke, Joachim Audenaert, Ruth Verhoeven, Bruno Gobin, Duc Tung Nguyen, Luc Tirry, Patrick De ClercqAbstract:BACKGROUND In integrated pest management systems in Greenhouse Crops, the predatory mite Amblyseius swirskii is becoming increasingly important as a biological control agent of various pests, especially thrips and whiteflies. An emerging strategy to promote the predator's establishment and retention in the crop consists in providing food supplements. However, when faced with omnivorous pests, such as the western flower thrips, Frankliniella occidentalis, food supplements need to be applied with extreme care, in order not to boost population growth of the pest. This laboratory study was conducted to evaluate the impact of commercial products of Typha angustifolia pollen and decapsulated brine shrimp cysts (Artemia sp.) on populations of both pest and predator and on predator–prey interactions. RESULTS Pollen was highly supportive for both F. occidentalis and A. swirskii, whereas Artemia cysts supported thrips populations to a lesser extent than those of the predator. Furthermore, a less pronounced reduction in thrips consumption by A. swirskii was observed in the presence of Artemia cysts as compared with T. angustifolia pollen. CONCLUSION Artemia might be a valuable alternative to pollen for supporting populations of A. swirskii in order to improve thrips management, as they are less beneficial for the pest but do support population growth of A. swirskii. © 2015 Society of Chemical Industry
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Interaction between Podisus maculiventris and Harmonia axyridis two predators used in augmentative biological control in Greenhouse Crops
BioControl, 2003Co-Authors: Patrick De Clercq, Ilse Peeters, Griet Vergauwe, Olivier ThasAbstract:Intraguild predation (IGP) betweenthe pentatomid Podisus maculiventris (Say) and the coccinellid Harmoniaaxyridis (Pallas) in the absence or presenceof the extraguild prey Spodopteralittoralis (Boisduval) and Myzuspersicae (Sulzer) was studied in thelaboratory. Interactions were asymmetric infavor of the pentatomid. Podisusmaculiventris readily fed upon eggs and larvaeof H. axyridis , but adult beetles wererarely attacked. Success of attacks by P.maculiventris was stage dependent, fourthinstars and adults being more successful inkilling ladybeetle larvae than second instars.Attacks by H. axyridis on the pentatomidwere rare and none of them were successful. Theeffect of introducing extraguild prey on thelevel of IGP was tested both in petri dishesand on caged sweet pepper plants. Whensufficient numbers of S. littoralis larvae were present to satiate the pentatomid,predation on H. axyridis larvae decreasedsignificantly, indicating that the coccinellidis a less preferred or less vulnerable prey.When the aphid M. persicae was presentedas extraguild prey, levels of IGP were notaltered. Nymphs of P. maculiventris successfully completed development whenexclusively fed on larvae of H. axyridis ,but developmental time was longer than onlepidopteran prey. No pentatomid nymphs reachedadulthood on aphids alone. IGP by P.maculiventris on H. axyridis may be ofsome importance in Greenhouse Crops, where bothpredators are being used increasingly inaugmentative biological control programs.Nonetheless, it is expected that in practicelarger larvae and adults of H. axyridis will escape most attacks by the pentatomid.
G M Steenhuisbroers - One of the best experts on this subject based on the ideXlab platform.
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comparative life history studies of frankliniella occidentalis and thrips tabaci thysanoptera thripidae on cucumber
Bulletin of Entomological Research, 1995Co-Authors: P C J Van Rijn, C Mollema, G M SteenhuisbroersAbstract:Shortly after its invasion into Europe, the western flower thrips, Frankliniella occidentalis (Pergande), became a more severe pest of Greenhouse Crops than the onion thrips, Thrips tabaci Lindeman. To test whether this differential pest status was due to a larger capacity of population increase, a comparative life history study was carried out on cucumber ( Cucumis sativus cv. Corona). Experiments at 25°C showed that the egg-to-egg period of F. occidentalis was shorter, but its peak ovipositional rate was lower and its offspring sex ratio more male biased. These differences resulted in a slightly lower intrinsic rate of population increase (r m ) for F. occidentalis than for T. tabaci (0.166 vs. 0.176/day). It was shown experimentally that between 15 and 28°C, developmental rate of F. occidentalis is linearly related to temperature, with a theoretical threshold temperature similar to the value reported for T. tabaci (10.9 vs. 11.5°C). It is argued that the r m -value of F. occidentalis will not be higher than that of T. tabaci for any temperature within this range. Alternative explanations for the difference in pest status between the two thrips species are discussed.
M. D. Fernández - One of the best experts on this subject based on the ideXlab platform.
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analysis of on farm irrigation performance in mediterranean Greenhouses
Agricultural Water Management, 2007Co-Authors: M. D. Fernández, A M Gonzalez, J Carreno, C Perez, Santiago BonachelaAbstract:Abstract A comprehensive irrigation assessment was conducted using on-farm water use information and simulated crop water requirements in a Mediterranean Greenhouse area, mainly dedicated to horticultural Crops, located on the Almeria coast. The mean irrigation water supply (IWS) for the main Greenhouse crop cycles was 228 mm and ranged from 158 mm (autumn green bean) to 362 mm (autumn–spring sweet pepper). Besides, the mean AIWS value for the main crop rotations was 444 mm and ranged between 363 mm for autumn–spring sweet pepper and 502 mm for autumn–winter pepper and spring melon. Mean relative irrigation supply (RIS) values were close to 1 for most Greenhouse vegetable Crops, indicating that, on average, the irrigation supply matched the maximum water requirements of these Crops. By contrast, the mean RIS value of autumn–winter cucumber was 1.6, indicating that, on average, the irrigation supply clearly exceeded the calculated optima. However, for most Crops, the high CV values observed for RIS and the analysis of the RIS dynamics throughout the cycles indicate that there are Greenhouse Crops and crop cycle periods for which the IWS clearly does not match the crop water requirements. Greenhouse irrigation water use in the Almeria coastal region can, therefore, be improved. Mean irrigation water use efficiency (IWUE) values for Greenhouse horticultural Crops ranged from 15.3 kg m −3 (autumn–winter green bean) to 35.6 kg m −3 (spring watermelon). They were, in general, higher than those found when these Crops were grown outdoors in similar climatic regions. Water productivity (WP) varied from 7.8 to 15.9 € m −3 and were highest for green bean Crops. WP values of Greenhouse Crops were generally much higher than those found in other irrigation districts around the world, including Mediterranean areas, due to the low IWS and, especially, to the high value of the vegetable Crops grown off-season.
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irrigation scheduling of plastic Greenhouse vegetable Crops based on historical weather data
Irrigation Science, 2006Co-Authors: Santiago Bonachela, Alicia Maria Gonzalez, M. D. FernándezAbstract:Irrigation scheduling based on the daily historical crop evapotranspiration (ETh) data was theoretically and experimentally assessed for the major soil-grown Greenhouse horticultural Crops on the Almeria coast in order to improve irrigation efficiency. Overall, the simulated seasonal ETh values for different crop cycles from 41 Greenhouses were not significantly different from the corresponding values of real-time crop evapotranspiration (ETc). Additionally, for the main Greenhouse Crops on the Almeria coast, the simulated values of the maximum cumulative soil water deficit in each of the 15 consecutive growth cycles (1988–2002) were determined using simple soil-water balances comparing daily ETh and ETc values to schedule irrigation. In most cases, no soil-water deficits affecting Greenhouse crop productivity were detected, but the few cases found led us to also assess experimentally the use of ETh for irrigation scheduling of Greenhouse horticultural Crops. The response of five Greenhouse Crops to water applications scheduled with daily estimates of ETh and ETc was evaluated in a typical enarenado soil. In tomato, fruit yield did not differ statistically between irrigation treatments, but the spring green bean irrigated using the ETh data presented lower yield than that irrigated using the ETc data. In the remaining experiments, the irrigation-management method based on ETh data was modified to consider the standard deviation of the inter-annual Greenhouse reference ET. No differences between irrigation treatments were found for productivity of pepper, zucchini and melon Crops.
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evapotranspiration of horticultural Crops in an unheated plastic Greenhouse
Agricultural Water Management, 2005Co-Authors: Francisco Orgaz, Santiago Bonachela, M. Gallardo, M. D. Fernández, Elias FereresAbstract:Abstract Large unheated Greenhouse areas are located in the coastal lands of the Mediterranean Basin, based on low-cost structures covered with plastic. Water is a scarce resource in these areas and therefore it is necessary to optimise irrigation practice by applying the crop water needs, thus avoiding waste. This work was undertaken to determine the water requirements of four major horticultural Crops grown in an unheated plastic Greenhouse located in Almeria, Spain. Drainage lysimeters were used to determine the seasonal evapotranspiration (ET) of four Crops (melon, green beans, watermelon and pepper), which ranged from 170 to 371 mm and it was associated with the reference ET (ET 0 ). Compared to irrigated Crops outdoors, the seasonal ET of the Greenhouse horticultural Crops is relatively low due to the lower evaporative demand inside the Greenhouse and to a further reduction in solar radiation transmission by whitening in late spring and summer. Additionally, off-season Greenhouse Crops are grown during low evaporative demand periods, thus the low water requirements. Crop coefficient ( K c ) curves were obtained for the four Crops under different conditions. The K c values varied with the crop, stage of development, and with management practices. Measured peak K c values for Crops, which were not vertically supported (melon and watermelon) were between 1 and 1.1, similar to the measured values for the same Crops under field conditions. By contrast, peak K c values for vertically supported (VS) Crops (melon, green bean and sweet pepper) varied between 1.3 and 1.4, which are higher than those reported for outdoors. The tall and open canopy structures of the VS Greenhouse Crops, their high leaf area indices, along with the high proportion of diffuse radiation inside the Greenhouse, allowed for more uniform light penetration within the canopies and ET rates in those Crops higher than those of the short, non-supported Crops. Management and climatic conditions combined to define an unusual K c curve for sweet pepper. The crop is transplanted in late summer and reaches the peak K c in early winter. Because of the low temperatures, K c decreased thereafter down to about 1.0, until climatic conditions inside the Greenhouse improved. From late winter to the end of the season, K c was either stable or increased steadily. A simple K c model based on thermal time for Greenhouse Crops with and without pruning, was proposed and validated. The model gave accurate estimates of measured K c values for melon and pepper.
