Guan'gai paishui xuebao (Nov 2022)
Effect of Sand Filter in Subsurface Drain on Water and Salt Movement in Paddy Soil
Abstract
【Background and objective】 Saline-alkali soils are widely distributed in Ningxia. Because of the scarcity of precipitation, such soils are often reclaimed by flooding rice field combined with subsurface drain. This paper presents the results of an experimental study of water and salt movement in a paddy field as affected by the sand filter in the subsurface drain. 【Method】 The field experiment was designed based on our current understanding and previous experimental results of the subsurface drains in different regions across the province. The experiment compared three filters: fine sand, mixture of fine sand and fine gravel sand at 1∶2 ratio and fine gravel. In each treatment, we measured spatiotemporal dynamics of soil water and soil salt. 【Result】 The filter with mixture of fine sand and fine gravel at 1∶2 ratio effectively reduced water content in the top 0~60 cm soil, increasing soil desalination during irrigation period as a result. Decrease in water content in the top 0~60 cm soil reduced evaporation, thereby alleviating salt accumulation in the root zone and reliveing salt stress to the crop. 【Conclusion】 The most effective filter for the subsurface drain in the studied paddy field is a mixture of fine sand and fine gavel at 1∶2 ratio.
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