Abstract: The study showed that under solar greenhouse condition,the contents of soil p-hydroxybenzoic acid,ferulic acid and benzoic acid and their total amounts increased with increasing continuous cropping years,and were obviously higher after continuously cropped for 5,7 and 9 years than for 1 and 3 years.Different concentration of soil phenols resulted in completely different effects on disease resistance-related enzyme activities in cucumber root,e.g.,under lower concentrations (40 and 80 μg·g^-1),the activities of phenylalanine(PAL),ployphenol oxidase(PPO) and peroxidase(POD) were increased,while under higher levels (120 and 160 μg·g^-1),they were restrained.Therefore,the changes of soil phenol contents in continuous cropping solar greenhouse could be one of the essential factors affecting the disease-resistance of cucumber.

Key words: Paddy soil, Methanogenesis, Iron oxide, Hydrogen, Carbon dioxide