Quantification of the Growth Response to Light Quantity of Greenhouse Grown Crops

Abstract

Growers have often assumed that a 1% increment in light results in a 1% yield increase. In this study, this rule of thumb has been evaluated for a number of greenhouse grown crops: fruit vegetables (cucumber, tomato, sweet pepper), soil grown vegetables (lettuce, radish), cut flowers (rose, chrysanthemum), bulb flowers (freesia, lily), flowering pot plants (poinsettia, Kalanchoe), and non-flowering pot plants (Ficus, Dracaena). A literature survey was first carried out on the effects of light on growth, dry matter production and partitioning, dry matter content and harvestable yield. Subsequently, yield data for cucumber, poinsettia and rose from commercial growers were analysed. Finally, growers were interviewed to assess their crop management in relation to the available light. For most crops a 1% light increment results in 0.5 to 1% increase in harvestable product. As a rule of the thumb the following values may be used: 0.8-1% for soil grown vegetables, 0.7-1% for fruit vegetables, 0.6-1% for cut flowers, 0.25-1.25 for bulb flowers, 0.5-1% for flowering pot plants and 0.65% for non-flowering pot plants. These are average values, which depend on several factors. For instance, the relative effect of light on growth is greater at lower light levels, at higher CO 2 concentrations and at higher temperatures. Consequently, the relative effect is larger in winter than in summertime. The effect of light on growth also depends on the duration and moment that the light level is changed. Besides a positive effect on yield quantity, light usually has a positive effect on quality as well. Light should not be considered as a separate growth factor in greenhouse horticulture, as it forms an integral part of the total farm management. Many growers, for instance, choose a higher temperature and adapt their plant density and cultivar choice when the light level is increased. INTRODUCTIONThe growth rate of a crop largely depends on the radiation it receives. Considering a given solar radiation, the grower has several options to increase the amount of incident light on a crop, such as building a greenhouse with high light transmissivity, or using assimilation light. On the other hand, the use of some measures such as screens may reduce the amount of incident light on the crop.In order to judge whether a measure affecting the light intensity is profitable, the grower needs to estimate its effect on production. For more than 20 years Dutch growers have usually taken a 1% additional light results in 1% additional growth and production as a rule of thumb. For cut flowers and pot plants there are indications that effects of light on production are less strong than in vegetable crops; for these crops 1% additional light it is often assumed to result in 0.5% additional growth and production.Light is the driving force for photosynthesis, while it may also affect plant development, morphology, dry matter partitioning and water content. Despite the assumed proportionality between light and production, it is well known that leaf p...

Greenhouse tomato production with electricity generation by roof-mounted flexible solar panels

“…Differences between the treatments were seen in terms of mean fruit mass and maximum diameter, with the physically largest fruits obtained in the T0 treatment, in which the EC was actually the highest (Table 4). Thus, the latter results may have been more the outcome of the lack of shading than any effect of EC (Cockshull et al, 1992;Papadopoulos and Parajasingham, 1997;Marcelis et al, 2006). The lower EC in T2 might be explained by differences between the treatments in the depth of the different growth substrate layers (Figure 2) plus possible differences in the speed of mineralisation of the manure layer.…”

Light Use Efficiency at Different Wavelengths in Rose Plants

“…Recent studies demonstrate that for most greenhouse crops a 1% increment of light results in a 0.5 to 1% increase in harvestable product, with a tendency to a smaller and more variable effect in cut flowers and pot plants (Marcelis et al, 2006). This "rule of thumb" does not take into account several internal physiological and external environmental factors at the leaf level: leaf photosynthesis saturates at high light, shows acclimation to the light level and is dependent on e.g., leaf age and position in the canopy; local environmental conditions, e.g., CO 2 concentration, temperature also affect leaf photosynthesis (Demitriades-Shah et al, 1994).…”

“…The lighting enhances plant growth which results in year round high production and good quality. This practice is, however, relatively expensive and the most common lighting systems (High Pressure Sodium -HPS lamps) may neither spectrally nor energetically be optimal (Heuvelink et al, 2006;Marcelis et al, 2006).850 low heat emission and potentially a high energy conversion efficiency in near future (Massa et al, 2008;van Ieperen et al, 2008). Narrow-band lighting devices are available in several colours, giving the opportunity to select the light spectrum that is photosynthetically the most favourable for the crop.…”

Use of Natural and Artificial Light in Horticulture - Interaction of Plant and Technology

“…In such regions, there is a rule, that 1% more light equals 0.5-1% more production (Marcelis et al, 2006). The exact production increase due to more light is depending on crop, cultivar, season and other growth factors.…”