Process-based humidity control regime for greenhouse crops

Self Cite

Botrytis cinerea is one of the main postharvest problems in gerbera cut flowers. There are clear differences among growers in the percentage of flowers showing symptoms of Botrytis infection after harvest. Because the factors causing these differences are uncertain, cultivation parameters of twelve different growers were followed and a nursery comparison was carried out. Gerbera flowers 'Dino' were sampled twelve times; six times in autumn 2006 and six times in spring of 2007. At the nurseries climate (air temperature, relative humidity, light intensity and CO 2 concentration) was logged, and plant density, plant age and other characteristics were monitored. Before each harvest Botrytis spores were trapped in the greenhouses and counted. After sampling, flowers were treated according to a standard transport simulation. Thereafter Botrytis infection was monitored, and statistical analyses were performed on the effect of the pre-harvest conditions on Botrytis infection in the postharvest stage. Clear influence of the spore level in the greenhouse was observed. When a sufficient number of spores were present in the greenhouse environment, the humidity level and the intensity and duration of irradiation had the strongest influence on infection. In general, factors those lead to a dry microclimate such as the use of ventilators, the use of supplemental lighting and a low plant density were related with a lower number of lesions on gerbera petals in the postharvest phase.

Section: Discussionmentioning

confidence: 99%

Effects of Growth Conditions on Postharvest Botrytis Infection in Gerbera a Nursery Comparison

Slootweg¹,

Körner²

2009

Self Cite

“…This corresponds rather well with the 7% energy conservation resulting from our calculations. The reduction found by Körner and Challa (2003a) increased considerably when temperature control was combined with optimal humidity control in the greenhouse (Körner and Challa, 2003b). Rosenqvist and Aaslyng (2000) developed a dynamic greenhouse climate control system (IntelliGrow) based on the ability of the plant to adapt to changes in light, temperature and CO 2 concentration.…”

Section: Discussionmentioning

confidence: 99%

Optimisation of Co2 and Temperature in Terms of Crop Growth and Energy Use

Dieleman¹,

Meinen²,

Marcelis³

et al. 2005

In current greenhouse climate control, temperature set points follow a pre-set trajectory based on absolute or solar time parameters, adapted only to instantaneous and daily radiation. CO 2 is supplied during a well defined period of the day until a maximum concentration is reached. However, the rate of CO 2 supply is strongly limited by the heat demand, since flue gases are the most commonly used source of CO 2 . Interactions between effects of light, temperature and CO 2 concentration on photosynthesis and crop growth are usually not taken into account. This study aims to make more efficient use of temperature and CO 2 by developing an optimised climate control system in which temperature and CO 2 are deployed such that energy use is minimised while maintaining crop production. Firstly, the diurnal temperature course resulting in a predefined daily mean value was optimised while minimising the heat demand. Most of the time, this resulted in higher day temperatures and lower night temperatures. Secondly, using the heat storage tank, the partitioning of the CO 2 associated with the daily heat demand was optimised, aimed at maximised photosynthesis. Simulation results showed that in the optimised climate control system 7% less energy was used and 2.5% more production was realised than in a standard climate. Testing the optimised climate control in a greenhouse experiment showed that in a sweet pepper crop 6% more energy could be conserved compared to that in the standard climate with similar production levels and fruit quality between the climate control treatments. INTRODUCTIONIn view of the Kyoto protocol (1997), Dutch horticulture and government have agreed to improve the energy efficiency by 65% in 2010 compared to 1980. Energy efficiency can either be enhanced through an increase in production or a reduction in absolute energy consumption. The latter implies that the availability of CO 2 from flue gases associated with the heating demand of greenhouses will be reduced. Hence, an efficient use of CO 2 is getting more important. At present, the greenhouse climate is commonly controlled by rather rigid set points for heating and ventilation. Climate control systems are set to limit temperature fluctuations, resulting in high ventilation rates when the sun is shining and in heating during the night. However, several studies have shown that most horticultural crops tolerate temporary deviations from the temperature set point, as long as the average temperature over 24 hours is kept constant (Bakker and Van Uffelen, 1988;Rijsdijk and Vogelezang, 2000). This so-called temperature integration allows heating to be shifted to times when the heat loss is low, thereby reducing the energy use (Körner and Challa, 2003a). Allowing the day time temperatures to increase, enables average 24 h temperature to be obtained at lower night temperatures. The decreased ventilation rates during the day result in higher CO 2 concentrations that can be realised with a certain rate of CO 2 supply, thereby increasing photosynthes...

“…Many attempts to reduce the energy input for greenhouses therefore have concentrated on the ventilation process and its effects on the heat-and mass transfer (e.g. Molina-Aiz et al, 2005;Valera et al, 2005;Baeza et al, 2006;Baeza, 2007;Sase, 2006) and the use of this knowledge in energy efficient operational control (Körner and Challa, 2003a). During periods with relatively low radiation and moderate ambient temperatures, natural or forced ventilation is generally used to prevent (too) high humidity and this is related to a significant (5 to 20%) fraction of the energy consumption (Campen et al, 2003).…”

Section: Minimize Energy Loss Through Ventilation and Latent Heatmentioning

confidence: 99%

“…The experimental test with this routine showed a slight but significant increase in energy efficiency. Another example of a step to successful energy efficient operational control is the model based humidity control (Körner, and Challa, 2003a) which improved the humidity routine to avoid fungal diseases like grey mold (e.g. Körner and Holst, 2005).…”

Section: Energy Efficient Operational Controlmentioning

confidence: 99%

Innovative Technologies for an Efficient Use of Energy

Bakker¹,

Adams²,

Boulard³

et al. 2008

Efficient use of energy in greenhouses has been subject of research and development for decades. The final energy efficiency, e.g. the amount of energy used per unit of product, is determined by improvements in energy conversion, reductions in energy use for environmental control and the efficiency of crop production. The new European targets on reduction of CO 2 emission have resulted in a renewed interest in innovative technologies to improve energy efficiency in greenhouses designed for North-as well as South European regions. In this paper an overview of the recent developments is presented from both the Northwest European as well as the Mediterranean perspective. The developments range from new modified covering materials, innovative and energy conservative climate control equipment and plant response based control systems, to integrated energy efficient greenhouse designs.