Spatial variability of soil salinity and organic matter in reclaimed area of abandoned salt pan in coast

Abstract: The southern area of Laizhou bay is located by the Bohai sea. There have been three seawater intrusion events in history, and a mass of high concentration saline brine has been buried in its subsurface aquifers. Large - scale exploitation of underground brine resources has been carried out since the 1970s. Brine baysalt has become a pillar industry of local economic development. In recent years, many salt pans become abandoned due to the exhaustion of regional shallow brine resources and the restriction of high cost and market factors of deep brine exploitation. In this context, some salt pans have been reclaimed based on the relevant government policies. Although a series of remediation measures that combining agriculture and engineering have been carried out on the reclaimed land of salt pans, the soil still contains a large amount of soluble salt on account of the influence of perennial baysalt process, moreover, the content of soil nutrients is also extremely low. The high soil salinity has always been the main limiting factor for the sustainable development of agriculture in the reclamation areas of abandoned salt fields. In this paper, soil sampling data of cotton growth period in four key nodes were used to study the spatial distribution characteristics of soil organic matter and soil salinity at different depths in different periods, and to analyze the correlation between them. The two-dimensional spatial distribution map of soil organic matter content and the three-dimensional spatial distribution map of soil salinity in different periods were drawn. The results showed that the variation of soil salinity and organic matter content at different depths in different periods in the study area was large, among which the maximum variation of organic matter content reached 37.3 g/kg and the maximum variation of soil salinity reached 57.2 g/kg, the variation intensity of both soil salinity and organic matter content was moderate. Soil salinity and organic matter content decreased with time change. The correlation between soil salinity and organic matter content in the soil layer of 0 - 30 cm was the highest, the range was from 0.25 to 0.38, but it did not reach the level of significant correlation. The correlation of soil salinity between different layers reached a significant or extremely significant degree. There was a moderate spatial autocorrelation between soil salinity and surface soil organic matter content. Kriging interpolation results showed that the surface soil organic matter content was distributed in a banded manner, the organic matter content increased gradually from west to east in seedling stage and flowering stage. The soil organic matter content in the flowering and boll period was the lowest in the northeast, and the highest in the harvest period was concentrated in the northwest and southeast. The three-dimensional spatial distribution of soil salinity was similar in different periods and different layers, and its spatial distribution characteristics were generally close. The high soil salinity area at seedling and flowering stage appeared in the southeast. The spatial distribution of soil salinity in flowering and flowering period was scattered and patchy. The results provide technical support for scientific improvement and rational utilization of saline soil and sustainable development of agriculture to the southern area of Laizhou Bay.