Adding carbon dioxide (CO_2) to enclosed greenhouse environments has long been recognised as a key method to boost crop growth and therefore yields. The technique has been used for everything from strawberries in tunnels to salad crops and ornamentalsunder glass, but how is a changing perspective on CO_2 in the natural atmosphere, together with changes to the way greenhouses are heated, affecting its supply and utilisation by professional growers? Writes Richard Crowhurst.AHDB's CO_2 best practice guide points out that, 'Carbon dioxide is an essential component of photosynthesis, which with light energy drives crop growth. For the majority of greenhouse crops, net photosynthesis increases as CO_2 levels increase. A widely followed rule of thumb suggests that for most crops at any given level of photosynthetically active radiation (PAR), increasing the level to 1,000 ppm will increase photosynthesis by about 50% over ambient CO_2 levels.'
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