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.


Project code:
PC 269
01 January 2007 - 01 February 2008
Project leader:
C T Pratt


PC 269 Final report 2008

About this project


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



  • 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.