Energy saving: From engineering to crop management

In greenhouse horticulture, energy costs form an increasingly larger part of the total production costs. Energy is primarily used for temperature control, reduction of air humidity, increase of light intensity and CO2 supply. Use of fossil energy can be reduced by limiting the energy demand of the system and decreasing energy losses, by intelligent climate control, by increasing the energy efficiency of the crop and by replacing fossil energy sources by sustainable ones. Energy requirement of the greenhouse can be lowered up to 20-30% by using greenhouse covers with higher insulating values and the use of energy screens. A prerequisite is that these materials should not involve considerable light loss, since this would result in a loss of production. In energy efficient greenhouse concepts, durable energy sources should be included. In (semi-)closed greenhouses, the excess of solar energy in summer is collected and stored in aquifers to be reused in winter to heat the greenhouse. Ventilation windows are closed, with specific benefits to the crop: high CO2 levels can be maintained, and temperature and humidity can be controlled to the needs of the crop. Development of new greenhouse concepts is ongoing. Current examples are greenhouse systems which convert natural energy sources such as solar energy into high-value energy such as electricity. Given a certain technical infrastructure of the greenhouse, energy consumption can be further reduced by energy efficient climate control and crop management. Essential elements are to allow fluctuating temperatures, lower crop transpiration, allow higher humidities, make efficient use of light and create fluent transitions in set points. Consequences for plant growth are related to rate of development, photosynthesis, assimilate distribution, transpiration and the occurrence of diseases or disorders. Since processes involved are complex, knowledge exchange between researchers and growers is essential to realize the goals set to reduce the energy consumption

Tuinder kan CO2 effectiever gebuiken

Een hoger kooldioxideniveau in de kas levert meer op als de dosering aansluit op hoeveel licht er beschikbaar is. Onderzoek van Wageningen UR Glastuinbouw laat zien dat met een nieuw teeltsysteem met dezelfde hoeveelheid CO2 tien procent meer productie is te behalen

Future proofing

Drastic improvements in growing technology in the Netherlands have achieved a large reduction in energy use and a striking increase in production

Cytokinins and bud break in rose combination plants

In the Netherlands, the rose is the most important glasshouse cut flower. Approximately 50% of the glasshouse roses are combination plants, consisting of a scion cultivar and a rootstock of a different genotype. Rootstocks inducing differences in the vigour of the scion are suggested to differ in cytokinin production and export to the shoot, thereby affecting bud break and outgrowth of the scion.In the present study, the course of endogenous cytokinins in rose combination plants was determined. The high contribution of isopentenyladenine-type cytokinins in young leaves indicated that these leaves, as the roots, were capable of de novo synthesis of cytokinins. Export of cytokinins from the roots was estimated based on the assumption that the cytokinin concentration in bleeding sap is representative for the concentration in xylem sap in situ , which was experimentally verified. The concentration of zeatin riboside (ZR) in bleeding sap was shown to be correlated with bud break of axillary shoots and bottom breaks, it increased before bud break and decreased thereafter. This suggests a quantitative relationship between cytokinin export from the roots and shoot development. Growth of the scion was also influenced by environmental factors, since bud break was advanced at higher root temperatures in the range of 11 to 26°C.However, this effect could not be correlated reliably with the cytokinin export from roots to shoot. Grafting the scion Madelon on rootstocks varying in vigour revealed that the rootstock that induces earlier bud break of the scion supplies larger quantities of cytokinins to the shoot. As a consequence, the concentrations of cytokinins in bleeding sap may be used as an early selection criterion for rose rootstocks.An attempt was made to describe correlative inhibition in rose. The apex of the primary shoot is thought tot exert apical dominance over the axillary buds along the shoot, until the terminal flower is visible. As at that time, the auxin export from the apex decreases, the inhibition of the uppermost 2-4 axillary buds is released, resulting in bud break. Later, the young axillary shoots will take over apical dominance and inhibit bud break further down the stem by their auxin production. When the terminal flower buds of the axillary shoots are visible, apical dominance is reduced, leading, following the same reasoning as above, to basal bud break.The effectivity of ZR in side-shoot formation, as was shown in in vitro experiments, combined with the fact that ZR is the major translocation form of cytokinins in the xylem points at a key role for ZR or its immediate metabolite, which might be zeatin, in growth and development of rose plants.</p

Comparison of climate and production in closed, semi-closed and open greenhouses

A (semi-)closed greenhouse is a novel greenhouse with an active cooling system and temporary heat storage in an aquifer. Air is cooled, heated and dehumidified by air treatment units. Climate in (semi-)closed greenhouses differs from that of conventional open greenhouses. The aims of our research were first, to analyze the effect of active cooling on greenhouse climate, in terms of stability, gradient and average levels; second, to determine crop growth and production in closed and semi-closed greenhouses. An experiment with tomato crop was conducted from December 2007 until November 2008 in a closed greenhouse with 700 W m-2 cooling capacity, two semi-closed greenhouses with 350 and 150 W m-2 cooling capacity, respectively, and an open greenhouse. The higher the cooling capacity, the more independent the greenhouse climate was of the outside climate. As the cooling ducts were placed underneath the plants, cooling led to a remarkable vertical temperature gradient. Under sunny conditions temperature could be 5°C higher at the top than at the bottom of the canopy in the closed greenhouse. Cumulative production in the semi-closed greenhouses with 350 and 150 W m-2 cooling capacity were 10% (61 kg m-2) and 6% (59 kg m-2) higher than that in the open greenhouse (55 kg m-2), respectively. Cumulative production in the closed greenhouse was 14% higher than in the open greenhouse in week 29 after planting but at the end of the experiment the cumulative increase was only 4% due to botrytis. Model calculations showed that the production increase in the closed and semi-closed greenhouses was explained by higher CO2 concentratio

Het Nieuwe Telen Aubergine: Effecten van een nieuw teeltconcept op kasklimaat en energiegebruik

Met het teeltconcept “Het Nieuwe Telen”, met als belangrijke onderdelen gebruik van meerdere schermen, scherpere vochtregeling en luchtbehandeling met buitenluchtaanzuiging en verwarming is tot ca. 40% energiebesparing te realiseren is. In 2010/2011 is het project “Het Nieuwe Telen Aubergine” uitgevoerd, met als doelstelling het opstellen van een teeltconcept waarmee 40% energiebesparing gerealiseerd zou moeten kunnen worden met behoud van productie en productkwaliteit

Schermen in de tomatenteelt: mogelijkheden en beperkingen

Het gebruik van energieschermen is een goed middel om energie te besparen en pieken in het gasverbruik te verlagen. In een onderzoekskas in Wageningen is een proef uitgevoerd in 4 kasafdelingen met Durinta planten. Uit fotosynthesemetingen is gebleken dat het licht direct na zonsopkomst niet belangrijker is dan het licht in de uren daarop volgend. Door het gebruik van een energiescherm in de tomatenteelt is 16% energie te besparen. Door het gebruik van het scherm te optimaliseren is nog 3% energiebesparing mogelijk, maar dit gaat wel snel ten koste van de producti

Gewasmanagement in semi-gesloten kassen: Simulaties van gewasgroei en -ontwikkeling

Experimenten van het project ‘Gewasmanagement bij geconditioneerd telen’ zijn met het Intkam simulatiemodel doorgerekend om te analyseren welke klimaatfactor in welke mate verantwoordelijk is voor verschillen in productie