Dynamics of groundwater table and soil desalination of platform fields in coastal wasteland

In this study, 135 cm, 145 cm, and 175 cm high platform fields were built on coastal saline wastelands in the Yellow River Delta. The dynamics of groundwater table were monitored over a period of 2 years and changes in soil salt content after 5 years crop cultivation were determined, with natural saline wastelands as the control. The main objective of the study was to provide data-driven technical support for large-scale agricultural development in coastal saline soils. The results of the 2-year consecutive monitoring showed that the three platform fields effectively increased saline water table. Groundwater table in saline wastelands changed in the range of 0.65~2.10 m, while those in the three platform fields changed in the range of 2.20~3.63 m. Compared with saline wastelands, groundwater salinity of the three platform fields significantly increased. This suggested that salts in platform fields leached from soil profile to groundwater via both irrigation and rainfall. Salt content in the 0~30 cm soil layer was 4.90~7.33 g·kg^-1 in saline wastelands, which significantly dropped to <1.37 g·kg^-1 after platform field development and irrigation. Desalination ratio of the platform fields was 81.31%~89.05%. Salt content in the 0~120 cm soil layer of the platform fields was lower than those of saline wastelands after 5 years cultivation. The differences in soil salt content between platform field and control field in both 0~30 cm and 30~60 cm soil layers were significant. Soil profile salt content in the 135 cm and 145 cm platforms was <1.62 g·kg^-1. The results indicated that “platform field-deep ditch” was an effective engineering measure to ameliorate salinity in coastal wastelands. In terms of cost and effective area ratio, the 145 cm high platform field was recommended the best practice for coastal wasteland desalination.