Effects of elevated CO 2 concentrations on growth and yield of eight vegetable species in a cool climate

Abstract

The effects of elevated CO 2 concentrations on the yield of Allium cepa (onion), Allium ampeloprasum (leek), Apium graveolens var. dulce (celery), Apium graveolens var. rapaceum (celery root), Brassica pekinensis (chinese cabbage), Daucus carota (carrot), Lactuca sativa (lettuce) and Petroselinum crispum (parsley) grown in containers, were studied in six 9-m 2 large field plots surrounded by 1.8-m high plastic foil walls (‘field chambers’). Three of the chambers were supplied with pure CO 2 gas through perforated tubes. Increasing the CO 2 concentration from ambient (355 μmol mol −1) to 800–900 μmol mol −1 increased the yield (fresh weight) by 23% in onion (two cultivars) and by 8% in carrot (three cultivars). The dry weight based yield increase was 18% in lettuce (three cultivars), 19% in carrot and 17% in parsley (one cultivar). The yields of leek (two cultivars), chinese cabbage (three cultivars), celery (one cultivar) and celery root (one cultivar) were not significantly affected by the CO 2 concentration. Generally, no ‘chamber effect’ was found on the yields of the different species.