Air humidity, stomata & transpiration

The plant's water status is the balance of water uptake and water loss. Transpiration (water loss) in influenced by sun, wind humidity, leaf area, and opening of stomatal pores in the leaves

Calculating light & lighting

Lighting in a greenhouse is surrounded by questions. How much light to supply and when?. What intensity and light sum to aim for? Is it radiation, light growlight, PAR, photons or quanta? How much is joule, watt, lux?. What does wavelength, nanometer, spectrum, UV, IR and NIR mean

Water use efficiency of tomatoes - in greenhouses and hydroponics

Massive amounts of water are required for the production of our food, varying from several cubic metres per kilogram of beef to as low as 4 litres per kilogram for tomatoes grown in high-tech glasshouses. This article presents data on Product Water Use (PWU) of some foods and discusses how the water requirement for fresh tomatoes can be brought down from 300 to 4 litres/kg

Institutional Stewardship and Ecology

We are not to exploit, waste, or abuse the resources of God\u27s world, but care for them and use them to serve God and humankind. Posting about becoming environmentally conscientious from In All Things - an online hub committed to the claim that the life, death, and resurrection of Jesus Christ has implications for the entire world. http://inallthings.org/institutional-stewardship-and-ecology

Future proofing

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

Energiezuinig klimaat in bioteelt en gewone teelt - proef 2009

Energy use can be reduced by highly insulating screens. The problem with screens is that less condensation occurs at the cold glass in the greenhouse roof. The two common methods of moisture control, screen gaps and use of minimum pipe temperature, require both a lot of energy. Therefore this research looked for another method to prevent the moisture problem. In this trial is that in principle forced ventilation with preheated air from outside. Also, the heating regime changed, that no minimum pipe temperature is set. This test showed that significant energy savings through a double screen are possible and through additional measures such as no minimum pipe to set and screens only open when the sun has more power. The extra screen can longer remain closed due to good humidity control (for heating dry air requires relatively little energy). Vertical gradients were low, partly due to the almost constant flow of Aircobreeze. The lower production observed may partly be due to lower CO2 and higher night temperatures

Energiebesparing in bio-glasteelten door intensief schermen en geavanceerd ventileren

Door intensief schermen in combinatie met geavanceerd ventileren en eventueel luchtbewegen werd een energiezuinige beheersing van temperatuur en luchtvochtigheid gerealiseerd. Op deze wijze krijgt Botrytis cinerea minder kans in de biologische tomatenteelt

Effects of CO2 concentration on photosynthesis, transpiration and production of greenhouse fruit vegetable crops

The effect of the C0 2 concentration of the greenhouse air (C) in the range 200 to 1100 μmol mol -1was investigated in tomato ( Lycopersicon esculentum Mill.), cucumber ( Cucumis sativus L.), sweet pepper ( Capsicum annuum L.) and eggplant ( Solanum melongena L.), grown in greenhouses.The effect of C on canopy net photosynthetic C0 2 assimilation rate (or photosynthesis, P) was expressed by a set of regression equations, relating P to PAR, C and LAI. A rule of thumb ('CO 2 -rule') was derived, approximating the relative increase of P caused by additional C0 2 at a certain C. This C0 2 -rule is: X = (1000/C) 2* 1.5 (X in % per 100 μmol mol -1, and C in μmol mol -1). Two models for canopy photosynthesis were examined by comparing them with the experimental photosynthesis data. No 'midday depression' in P was observed.The effects of C on leaf conductance ( g ) and on rate of crop transpiration ( E ) were investigated. An increase of 100 μmol mol -1in C reduced g by about 3-4% in sweet pepper, tomato and cucumber and by about 11 % in eggplant. The effect of C on E was analyzed by combining the regression equation for g with the Penman-Monteith equation for E . C had only a relatively small effect on E , owing to thermal and hydrological feedback effects. The decoupling of g and E was quantified. No timedependent variation or 'midday depression' in E was observed, and no significant effect of C on average leaf temperature was established.In five experiments, the effect of C on growth and production and on specific features were analyzed: light use efficiency was increased by about 10 to 15% per 100 μmol mol -1increase in C; fruit set of sweet pepper was greatly increased by high C; allocation of biomass to fruits was increased by high C in sweet pepper and cucumber; specific leaf area (SLA) was reduced by 15 to 20% at 150 to 250 μmol mol -1increase in C (except in cucumber); dry matter content (DMC) of vegetative organs slightly increased at high C (also not in cucumber); fruit production (dry weight) was most affected by C in sweet pepper; fresh weight fruit production per unit CO 2 was highest in cucumber; fruit quality was not influenced by C. High C promoted the 'short leaves syndrome' in tomato and 'leaf tip chlorosis' in eggplant, probably related to calcium and boron translocation, respectively. The observed effect of C on production was larger than expected on the basis of the CO 2 -rule. Intermittent CO 2 supply (ICS) could under normal ventilation accomplish only a limited increase in average C, and hence a limited increase in production. No physiological advantages of ICS were revealed