Carbon dioxide enrichment by composting in greenhouses and its effect on vegetable production

Abstract Concentrations of CO 2 are commonly suboptimal for plant production in greenhouses. Here, a new strategy using crop‐residues and animal‐manure composting (CRAM) was developed to increase CO 2 concentration throughout the day. During the whole cultivation period, CRAM‐treated greenhouses had CO 2 concentrations that were more than twice that of the control greenhouses. This resulted in yields of celery ( Apium graveolens L.), leaf lettuce ( Lactuca virosa L.), stem lettuce (Lactuca saiva L.), oily sowthistle ( Sonchus oleraceus L.), and Chinese cabbage ( Brassica chinensis L.) that were 270%, 257%, 87%, 140%, and 227% higher than those in control greenhouses, respectively. The effect of CRAM on vegetable‐quality parameters was also examined. Nitrate concentrations deceased in celery, leaf lettuce, oily sowthistle, and Chinese cabbage by 8%, 36%, 30%, and 20%, respectively. The concentrations of soluble sugars in oily sowthistle and Chinese cabbage were significantly increased by the composting procedure. In addition, the ascorbic acid concentrations increased in all five species, with average increases of 13%, 39%, 25%, 72%, and 37% for celery, leaf lettuce, stem lettuce, oily sowthistle, and Chinese cabbage, respectively. It is concluded that CO 2 fertilization using CRAM in greenhouses increases yields and improves quality of common vegetables.