Soil salination challenges sustainable agricultural production and management in the lowland area of the North China Plain (NCP). This study investigated the effect of varied rainfall events and hydrological years on deep drainage and salt leaching in Nanpi County in the NCP. Field experiments were conducted to measure soil matric potential (SMP) and soil water electrical conductivity (EC_w) in 300 cm profiles of an irrigated cropland (CL) and unirrigated grassland (GL). The HYDRUS-1D model was calibrated and validated to optimize soil water and salt transport parameters using the SMP and EC_w data obtained in 2015 and 2016, respectively. The results showed that the HYDRUS-1D model was reliable to simulate soil water and salt migration in 300 cm profiles at both sites. The salt leaching depths and degrees were positively correlated with precipitation amount. The heavy rain (45 mm) and rainstorm (68 mm) favored salt leaching within 100 cm, and severe and extreme rainstorms resulted in salt leaching within 150–200 cm both in the CL and GL. The SDP in the CL was greater than that in the GL in all hydrological years owing to agricultural cultivation and irrigation. Salt leaching in the 300 cm profiles mainly occurred in the rainy seasons of wet year, with the salt decrease percentage (SDP) being 61% in the CL and 42% in the GL. Salt leaching due to precipitation was sufficient in the irrigated CL in all hydrological years, and precipitation in normal rainfall years could remove 70–80% of soil salts within 50–63 cm soil depth. Grass growth without irrigation led to water deficits and salt accumulation when the annual precipitation amount was less than that in wet years. The results demonstrated that precipitation, combined with irrigation using of brackish and freshwater, could be usefully for soil salt leaching. A recommended irrigation scheme for water saving and salt control in CL and GL is one brackish water irrigation application and three freshwater irrigation applications each year in the NCP.

土壤盐渍化对华北平原（NCP）低地地区的可持续农业生产和管理提出了挑战。本研究调查了不同降雨事件和水文年对华北地区南皮县深层排水和盐浸的影响。进行田间试验以测量灌溉农田 (CL) 和未灌溉草地 (GL) 的 300 厘米剖面中的土壤基质电位 (SMP) 和土壤水电导率 (EC _w )。_{使用 SMP 和 EC w}校准和验证 HYDRUS-1D 模型以优化土壤水和盐传输参数分别在 2015 年和 2016 年获得的数据。结果表明，HYDRUS-1D 模型能够可靠地模拟两个地点 300 cm 剖面中的土壤水和盐迁移。盐浸深度和浸出程度与降水量呈正相关。大雨（45 mm）和暴雨（68 mm）有利于100 cm范围内的盐淋，大雨和极端暴雨导致CL和GL都在150-200 cm范围内发生盐淋。由于农业种植和灌溉，CL 的 SDP 在所有水文年都大于 GL。300 cm剖面盐淋主要发生在雨季雨季，其中CL为61%，GL为42%。在所有水文年份，灌溉 CL 中由于降水引起的盐分浸出是充分的，正常降雨年份的降水可以去除 50-63 cm 土壤深度内 70-80% 的土壤盐分。当年降水量小于丰水年时，不灌溉的草生长导致水分亏缺和盐分积累。结果表明，降水与使用咸淡水和淡水灌溉相结合，可用于土壤盐分淋溶。在 CL 和 GL 中，推荐的节水和控盐灌溉方案是在 NCP 中每年进行一次微咸水灌溉和三次淡水灌溉。结果表明，降水与使用咸淡水和淡水灌溉相结合，可用于土壤盐分淋溶。在 CL 和 GL 中，推荐的节水和控盐灌溉方案是在 NCP 中每年进行一次微咸水灌溉和三次淡水灌溉。结果表明，降水与使用咸淡水和淡水灌溉相结合，可用于土壤盐分淋溶。在 CL 和 GL 中，推荐的节水和控盐灌溉方案是在 NCP 中每年进行一次微咸水灌溉和三次淡水灌溉。