Abstract
Groundwater is the main water resource for plant growth and development in the saline soil of the Yellow River Delta in China. To investigate the variabilities and distributions of soil water and salt contents at various groundwater level (GL), soil columns with planting Tamarix chinensis Lour were established at six different GL. The results demonstrated the following: With increasing GL, the relative soil water content (RWC) declined significantly, whereas the salt content (SC) and absolute soil solution concentration (CS) decreased after the initial increase in the different soil profiles. A GL of 1.2 m was the turning point for variations in the soil water and salt contents, and it represented the highest GL that could maintain the soil surface moist within the soil columns. Both the SC and CS reached the maximum levels in these different soil profiles at a GL of 1.2 m. With the raise of soil depth, the RWC increased significantly, whereas the SC increased after an initial decrease. The mean SC values reached 0.96% in the top soil layer; however, the rates at which the CS and RWC decreased with the GL were significantly reduced. The RWC and SC presented the greatest variations at the medium (0.9–1.2 m) and shallow water levels (0.6 m) respectively, whereas the CS presented the greatest variation at the deep water level (1.5–1.8 m).The RWC, SC and CS in the soil columns were all closely related to the GL. However, the correlations among the parameters varied greatly within different soil profiles, and the most accurate predictions of the GL were derived from the RWC in the shallow soil layer or the SC in the top soil layer. A GL at 1.5–1.8 m was moderate for planting T. chinensis seedlings under saline groundwater conditions.
Highlights
Shallow groundwater is the primary factor affecting the migration, accumulation and release of soil salt
Responses of relative soil water content to different groundwater level (Fig 2A–2E) shows that the RWC in different soil layers significantly decreased with increases in the GL and displayed a negative correlation at the extremely significant level
To indicate the level of RWC decreases with GL, the slope of the linear relationship between the RWC and GL was descried as the decreasing rate of the RWC with GL, which was significantly reduced with increasing soil depth
Summary
Shallow groundwater is the primary factor affecting the migration, accumulation and release of soil salt. Differences in the groundwater table can lead to the variability of soil water and salt contents, with subsequent effects on the growth, development and distribution of vegetation [1,2]. Responses of Soil Water and Salt Parameters to Groundwater Levels which is an important focus of investigations into the hydrological cycle and physical soil water processes [3,4,5]. The interaction effects and action processes of GL with soil water and salt in the soil profile remain unclear, leading to difficulties in saline land improvement and water-salt interaction stress, which affects plant growth because of changes in the GL. Studying the migration characteristics of water and salt in the soil and their interactions with GL can help increase the effective prevention against and control of secondary soil salinization at shallow groundwater levels
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