Soil organic carbon (SOC) and humus components ( humic acid

fluvic acid

and humin etc.) in the soil layer of 0 - 80 cm under three irrigation modes (furrow irrigation

drip irrigation and subsurface irrigation) were studied through 13 years of continuous tomato cultivation irrigation experiment. And the effect of irrigation methods on the properties of soil organic matters in greenhouse was evaluated. The results demonstrated that SOC content and the contents of humus components in three treatments declined with the increasing of soil depths. This kind of change mainly concentrated in the 0 - 50 cm soil layer

and the change in 50 - 80 cm soil layer was less. However

the SOC and its components were significant different among irrigation methods. The soil profile was divided into two layers

the upper (0 - 20 cm) and the lower (20 - 80 cm). The total SOC contents in the upper layer of three irrigation methods was in the order of subsurface irrigation > furrow irrigation > drip irrigation

and in the lower layer the order was drip irrigation > furrow irrigation > subsurface irrigation. For soil humus acid contents of three irrigation methods

in the upper layer the order was drip irrigation > furrow irrigation > subsurface irrigation

and in the lower layer

the order was subsurface irrigation > drip irrigation > furrow irrigation. For soil humin contents of three irrigation methods

in the upper layer the order was furrow irrigation > drip irrigation > subsurface irrigation

and the humin content in the lower layer was in the order of subsurface irrigation > drip irrigation > furrow irrigation. Drip irrigation could make the SOC content remain at a high level in the 0 - 40 cm soil layer

and soil humus content was higher than that of the other two irrigation methods

and this was beneficial to improve the soil fertility level and ensure the nutrient supply of tomato.