Rules of CO_2 concentration change under organic soil cultivation and effects of CO_2 application on tomato plants in solar greenhouse

The change rules of CO_2 concentration in greenhouse and tomato physiological effects were analyzed under organic soil cultivation.The results showed that there were space and season differences of CO_2 concentration in greenhouse.Highest diurnal CO_2 concentration in November and March was above 1 200 μL·L~(-1).No application or less application can be used in greenhouse in the case of improving temperature and radiation conditions.Highest diurnal CO_2 concentration in July was less than 500 μL·L~(-1).It is necessary to add CO_2 earlier everyday.The order of spatial distribution of CO_2 concentration is the groundthe surfacethe interiorthe cresthe upper.Diurnal change range of CO_2 concentration in organic soil cultivation is 331~1294 μL·L~(-1);and the range in soil cultivation without crop and outsides was 327~556 μL·L~(-1).Photon flux density is the most important environmental factor affecting CO_2 concentration in greenhouse.Comparing with CK,18.29% more height,18.69% more total dry weight,22.02% more leaf area,48.92% more photosynthetic rate,33.00% more chlorophyll content,87.50% more carboxylation efficiency,26.48% more yield,33.27% more Vc,30.98% more red element in fruits were obtained with CO_2 application.