Abstract:

In this paper, we studied the patterns of soil water movement in poplar plantation with a ground drip irrigation system on sandy land of ancient Yongding River in Beijing by observing soil profile in the field. We measured the movement distance of wet soil front and the shape of wet soil body under condition of various durations of drip irrigation with a constant flow rate of 4 L·h^-1. The results showed that: the movement distance of wet soil front in the vertical and horizontal directions increased with increased duration of drip irrigation. The increment of wet front movement distance in vertical direction decreased, while the increment of wet front movement distance in horizontal direction varied in a given range, with each 1 hour increase of irrigation time. the movement of wet soil front continued to migrate for 1-3 h in the vertical and horizontal directions for 1-3 h with the movement distance of 2-10 cm in vertical direction and 1-10 cm in horizontal direction at various soil depths except for at the deepest soil layer that was significantly larger than other soil depths, after stopping drip irrigation with various irrigation durations. The wet soil front moved to the end 36-69 cm in vertical direction and 32-57 cm in horizontal direction after drip irrigation for 1-6 h, while a wet soil body with a radii of 30-40 cm around the dripper at soil layers of 0-40 cm formed after drip irrigation for 3-4 h. After drip irrigation for 1-3 h, the wet soil body was gradually developing into an oblate ellipsoid, while the wet soil body developed into an prelate ellipsoid after drip irrigation for 4-6 h.

Key words: poplar plantation, drip irrigation, soil water movement, wet soil front, wet soil body