Cooling systems in screenhouses: Effect on microclimate, productivity and plant response in a tomato crop

• Plastic sheeting with fogging system improved screenhouse microclimate.
• Fogging system altered fruit load affecting their number and mass average.
• The increase in fruits fresh mass was due to water content and not dry weight.
• Increased water transfer into the fruit modified the sink-source relationship.

Mediterranean climates are characterised by summer temperatures that exceed 35 °C, high solar radiation ∼ 30 MJ m−2, relative humidity < 20% at around midday, and limited water resources generating yield loss in crops. For this reason, new climate strategy for greenhouses used in Mediterranean climates has been developed to avoid plant injury. Cherry tomato plants were assessed during 2010 and 2011 under different environmental conditions, namely in a screenhouse (S), in a screenhouse equipped with a fogging system (SF) and in a screenhouse with a plastic sheeting to maintain the microclimate created by the fogging system (SFS). SFS improved microclimatic conditions during the 2010 and 2011 growing seasons by, reducing incident radiation 37% and 30%, respectively while increasing relative humidity by 20% and 16%, respectively and respect to S lowering the vapour pressure deficit. These adjustments in microclimate could moderate the extremes of microclimate during the summer, avoiding episodes of physiological stress that affect yield and final quality. The dry mass vegetables plants parts grown under SFS increased while the marketable mass per plant was not significantly different. This was due to 45% increased in mean tomato fruit mass in 2010 and by 20% in 2011. Although tomato leaves grown under SFS registered the lowest values in foliar temperature, they showed the highest values for LAI, SLA, and LAR. It was concluded that a fogging could improve the climatic conditions under screenhouse and extend the growing season during adverse environmental conditions.