Deliverable 4. A model to quantify the effects of climate control devices (movable shading and fogging) on water uptake (CIFA & IRTA)

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Water is quite often a scarce natural resource in areas with warm spring and summer seasons. For this reason, there is the need to know the water consumption of greenhouse crops. A sensible use of water for irrigation requires the knowledge of crop transpiration over time intervals of a few minutes, but to determine the transpiration rate, the greenhouse microclimate has to be known (Stanghellini, 1992). 

 The main factors that contribute to determine the greenhouse daytime climate, the period when most transpiration takes place, are:

• Available solar radiation, which if needed may be partially reduced by shading.

• Evapotranspiration of the crop.

• Ventilation.

• Cooling by water evaporation (fogging systems, cooling system, etc.)

So, the greenhouse microclimate affects transpiration, but also transpiration has a strong effect in the internal climate. Therefore any climate control device like shading or evaporative cooling is expected to have an effect on the greenhouse climate and consequently on the transpiration rate. To study the interactions between plant response and climate, models based on the energy and mass continuity equations have been widely used.

This deliverable first presents a simplified greenhouse climate and transpiration model that is later validated by comparison with experimental measurements. The model is then incorporated in an executable Excel file that is used to make predictions of transpiration rate as a function of the external climate, leaf area index and climate control devices (shading and fogging)