JIA-2019-11

2476 ZHANG He et al. Journal of Integrative Agriculture 2019, 18(11): 2472–2482 3.2. The effect of groundwater depth on soil moisture and salinity During the 2-year experiment, at the two soil depths, the SRMC and EC 1:5 values were negatively related with groundwater depth in each growth stage (Fig. 3). The results of the linear fit showed that SRMC and EC 1:5 were positively related (Fig. 4). The average SRMC for the soils and groundwater depths for each period ranged from a minimum of 71.33% (ripening stage) to a maximum of 77.15% (jointing stage) in Y1, and from a minimum of 73.68% (seedling stage) to a maximum of 80.99% (jointing period) in Y2. Furthermore, the corresponding mean values for EC 1:5 ranged from a minimum of 0.97 dS m –1 (jointing stage) to a maximum of 1.22 dS m –1 (ripening stage) in Y1, and during Y2, it was in the range of 0.86 (jointing and booting stages) and 0.99 dS m –1 (seedling stage) (Fig. 3). In Y1 and Y2, the SRMC for S2 showed greater values, compared with the values for S1 (Fig. 3); likewise, the EC 1:5 for S2 displayed smaller values, compared with the values for S1 for the two wheat growing seasons (Fig. 3). The salinity classification standard based on EC 1:5 for sandy loam and the moisture classification standard (water logging, more than 85.0% SRMC; standard soil moisture, 67.6–85.0% SRMC; slight drought, 52.6–67.5% SRMC; medium drought, 40.0–52.5% SRMC) with some modifications had been applied (Zhang H et al . 2017). The soil exhibited water logging with high salinity (groundwater depth at 0.7 m), standard soil moisture with high salinity (1.1 and 1.5 m), standard soil moisture with medium salinity (1.9 m), slight drought with medium salinity (2.3 m), and slight drought stress with low salinity (2.7 m) in Y1 (Table 3). Whereas, in Y2, the soil showed water logging a b c d e e a b b c d d a b c c d d a b c d d e a b c d de e a b b c d e a b c d e e a b bc c d e a b c d e e a b b c d e a b b c d d a b b c d e a b c c d e a b c d e f a b c d e e a b b c d e a b c d e e a b c d e f a b c d e e a b b c c d a b c d d e a b c d e f a b b c d e a b b c c d a b c d e f a b c d e f a b b c d e a b c d e f a b c d e f a b c d e e a a b c d e a b c d e f a b b c d e a b c d e e a b b c d e a b c d e e a b c d e f a b c d e e a b b c d e a b b c d d 0 30 60 90 120 Groundwater depth (m) EC 1:5 (dS m –1 ) SRWC (%) 0–20 cm soil depth 20–40 cm soil depth 2013–2014 SS 2013–2014 JS 2013–2014 BS 2013–2014 FS 2013–2014 RS 0 30 60 90 120 2014–2015 SS 2014–2015 JS 2014–2015 BS 2014–2015 FS 2014–2015 RS 0.0 0.6 1.2 1.8 2.4 2013–2014 SS 2013–2014 JS 2013–2014 BS 2013–2014 FS 2013–2014 RS 0.0 0.6 1.2 1.8 2.4 2014–2015 SS 2014–2015 JS 2014–2015 BS 2014–2015 FS 0.7 1.1 1.5 1.9 2.3 2.7 0.7 1.1 1.5 1.9 2.3 2.7 0.7 1.1 1.5 1.9 2.3 2.7 0.7 1.1 1.5 1.9 2.3 2.7 0.7 1.1 1.5 1.9 2.3 2.7 0.7 1.1 1.5 1.9 2.3 2.7 0.7 1.1 1.5 1.9 2.3 2.7 0.7 1.1 1.5 1.9 2.3 2.7 0.7 1.1 1.5 1.9 2.3 2.7 0.7 1.1 1.5 1.9 2.3 2.7 0.6 1.0 1.4 1.8 2.2 2.6 0.6 1.0 1.4 1.8 2.2 2.6 0.6 1.0 1.4 1.8 2.2 2.6 0.6 1.0 1.4 1.8 2.2 2.6 0.6 1.0 1.4 1.8 2.2 2.6 0.6 1.0 1.4 1.8 2.2 2.6 0.6 1.0 1.4 1.8 2.2 2.6 0.6 1.0 1.4 1.8 2.2 2.6 0.6 1.0 1.4 1.8 2.2 2.6 0.6 1.0 1.4 1.8 2.2 2.6 2014–2015 RS Fig. 3 The soil relative moisture content (SRMC) and the conductivity with the 1:5 distilled water/soil dilution (EC 1:5 ) of 0–20 cm and 20–40 cm soil depths at the seedling stage (SS), jointing stage (JS), booting stage (BS), filling stage (FS), and ripening stage (RS). All values are means of three replications±standard error; values followed by different lowercase letters within the same style columns are significantly different at P <0.05 probability level. Table 2 The actual groundwater depth (m) in coastal saline soil Period Seedling stage Jointing stage Booting stage Filling stage Ripening stage Average 2013–2014 0.8 0.5 0.7 0.6 0.9 0.7 2014–2015 0.7 0.5 0.5 0.6 0.6 0.6