Linkage between soil salinization indicators and physicochemical properties in a long-term intensive agricultural coastal reclamation area, Eastern China

Abstract

Soil salinization is a major restricting factor for crop growth and agriculture productivity in coastal areas. Exploring the evolution of soil salinization indicators and physicochemical properties and their relationships in a long-term scale can provide a basis for the restoration, utilization, and prediction of coastal salinized soil. This study aimed to investigate the impact of reclamation years on soil salinization indicators and physicochemical properties in reclaimed coastal tidal land, and analysis the linkage between soil salinization indicators and physicochemical properties after long-term reclamation. Soil sample sites were respectively collected from reclamation regions reclaimed in 1951, 1974, 1982, and 2007 according to typical land use types. Besides, the natural tidal flat was collected as control. Soil samples were divided into two parts to determine soil bulk density (BD), soil water content (SWC), soil particle size distribution (PSD), soil salt content (SSC), pH, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), organic matter (SOM), alkaline hydrolyzed nitrogen (AN), and available phosphorus (AP). One-way analysis of variations (ANOVA) was conducted to investigate the differences in soil properties within different reclamation years. The linkage between soil salinization indicators and soil physicochemical properties was analyzed by redundancy analysis and Monte Carlo permutation. Compared with uncultivated tidal land, soil salinization indicators (SSC, pH, SAR, and ESP) significantly decreased after 30 years reclamation owing to the natural leaching and field management. Soil nutrients (SOM, TN, TP, AN, AP, CEC) apparently increased after reclamation of 30 years due to long-term fertilization. Moreover, SWC, BD, and SAND gradually decreased, whereas SILT and CLAY gradually increased after reclamation of 61 years. Soil salinization indicators were observed have a positive correlation with SAND and a negative correlation with SILT, CLAY, and soil nutrients. Long-term reclamation could radically decreased soil salinization (SSC, pH, SAR, ESP) and apparently promoted soil nutrients accumulation (SOM, TN, TP, AN, AP, CEC). Furthermore, soil salinization indicators are closely related to soil physicochemical properties, and soil PSD and soil nutrients were considered as the key factors for the differences of soil salinization.