Soil water and salt movement under drip irrigation of the ridge pattern in low-laying heavy saline alkali land

ObjectiveUnder "drip irrigation+ridge" pattern in saline alkali land, the survival rate of plants was high at the beginning but reduced by a big margin latter when plants were planted in furrow. Aiming to have a clear understand of why plants died in furrow, water and salt movement experiment under "drip irrigation+ridge" pattern was conducted.

MethodDrip tapes were arranged on both ridges and furrows after ridging in field and sustained drip irrigation was carried out under condition that there was not a large area of clear water around drip emitters. And the relationship between irrigation water amount and the water and salt movement of both ridge and furrow was analyzed by successively soil sampling, which were sampled upon wet front movement and the movement of water and salt.

ResultWhen no more than 41.4 mm water was irrigated, the distances of both horizontal and vertical wet fronts increased in considerably power function relationship with the increase of irrigation water amount. A soil zone with high water content and low salinity was formed directly under drip emitter displaced on ridge. This soil zone enlarged both on horizontal and vertical directions with the increase of irrigation water. When 84.3 mm water was irrigated, the contours of water content in elliptical shape converted to the shape that almost parallel to ridge slope. The two wet fronts formed by drips on ridge and in furrow, respectively, connected at an area, where the salt accumulated here. When 100.9 mm water was used, the salt in ridge moved continuously to deeper soil layer and the furrow, resulting in the contours of salt changing from double "U" shape to the shape that almost parallel to ridge slope. The salt leached from ridge accumulated in furrow heavily in this period. When 171.6 mm water was irrigated, the ridge had a great salt decrease, and soil salt got a 62.9% loss compared with the initial value.

ConclusionIrrigation under "drip irrigation + ridge" pattern had remarkable influence on water and salt movement on both ridges and furrows and the salt concentration in furrow reduced first, then increased later, and reduced again finally, revealing that desalination of furrows was delayed than that of ridges. To avoid the period of concentration of salt to furrows, vegetation constructions in furrows should be delayed than that on ridges.