Sweet peppers: The use of thermal screens for summer shading on plant growth and fruit quality

• Closing a thermal screen to 75% to provide shade at outside light intensities greater than 600W/m2 had no detrimental effect on yield or disease in 2007.
• None of the data collected indicated that photosynthesis was limited by extremes of temperature or humidity in the greenhouse in 2007.
• Weather conditions in the summer of 2007 were relatively mild compared to 2006 and the incidence of high temperature and high humidity deficit in the greenhouse was significantly less as a direct result.
• Sap flow can provide a real-time indication of plant ‘health’ and can be use in a commercial situation if it can be reliably and easily measured.
• Water uptake although simple and reliable to measure does not provide sufficiently frequent data to allow real-time application to identify plant stress and trigger screens to close.
• Water uptake is a useful indicator of plant health / activity when viewed as the total per day and compared with the light received.

AIM:

To examine the practical risks and benefits and evaluate sensible control boundaries for the use of thermal screens applied to crop shading.

OBJECTIVES:

• To quantify the effect of summer shading using a thermal screen on the yield, quality and disease levels in a commercial sweet pepper crop.
• To develop a shading screen control strategy to reduce the occurrence of stress inducing conditions.
• To identify the aerial environment that causes plant stress (indicated by stomatal closure and reduced transpiration) in a commercial sweet pepper crop
• To validate the use of water uptake, measured as volume applied minus drain volume, in relation to light as an indicator of plant stress.