Heating and CO2 enrichment in improved low-cost greenhouses

Two levels of climate control: heating and heating with CO2 enrichment, were compared with the conventional unheated control in improved low-cost greenhouses on the Mediterranean South Coast of Spain. Their effect on the crop growth, yield and water efficiency were evaluated in a autumn-winter cucumber soilless crop. The pure CO2 was supplied linked to automatic vents operation: 600 mumol mol(-1) with closed windows and 350 mumol mol(-1) when these opened up. Heating increased cucumber production (fruits per m(2)) mainly due to the shortening of the fruit growth period. Yield was significantly increased by climate control, in a 25.9 and 24.3 % with the application Of CO2 enrichment and heating respectively and 56.4 % with both systems. Similarly, the water supply efficiency was improved in a 28.7, 15.1 and 48.1 % respectively, for the CO2 enrichment, heating and both systems. Stem elongation and leaf production were enhanced by heating, whereas the CO2 application increased leaf production before fruit set.