Effect of different water application intensity and irrigation amount treatments of microirrigation on soil-leaching coastal saline soils of North China

In coastal regions, Bohai Gulf is one of the most affected areas by salinization. To study the effects of mocrosprinkler irrigation on the characteristics of highly saline sandy loam soil (ECe (saturated paste extract)=22.3 dS m−1; SAR (sodium adsorption ratio)=49.0) of North China, a laboratory experiment was conducted. Five water application intensity (WAI) treatments (1.7, 3.1, 5.3, 8.8, and 10.1 mm h−1), five irrigation amount (IA) treatments (148, 168, 184, 201, and 223 mm) and three time periods of water redistribution (0, 24 and 48 h) were employed in the study. A compounding microsprinkler system was used for the WAI treatments, and a single microsprinkler was used for the IA treatments. The results indicated that, as soil depth increased, soil water content (θ) increased and then slightly decreased; with WAI and IA consistently increasing, the relatively moist region expanded and the average θ increased. Meanwhile, soil ECe increased as soil depth increased, and the zone with low soil salinity expanded as WAI and IA increased. Although the reduction of the average SAR was smaller than that of the average electrical conductivity of the ECe, these variables decreased in similar fashion as WAI and IA increased under microsprinkler irrigation. The average pH decreased as soil depth increased. Longer time periods of water redistribution led to lower salinity and slight expansion of the SAR zone. Considering the effects of leached salts in coastal saline soils, greater WAI and IA values are more advantageous under unsaturated flow conditions, as they cause better water movement in the soil. After leaching due to microsprinkler irrigation, highly saline soil gradually changes to moderately saline soil. The results provide theoretical and technological guidance for the salt leaching and landscaping of highly saline coastal environments.