JIA-2019-11

2480 ZHANG He et al. Journal of Integrative Agriculture 2019, 18(11): 2472–2482 0.7 1.1 1.5 1.9 2.3 2.7 0 20 40 60 80 100 0.6 1.0 1.4 1.8 2.2 2.6 Grain yield of wheat (g/pot) n =6, df =3 n =6, df =3 GY=–41.5×GWD 2 +169.6×GWD–82.7 R 2 =0.9159 * 2013–2014 GY=–34.1×GWD 2 +142.7×GWD–58.6 R 2 =0.8622 * 2014–2015 Groundwater depth (m) Fig. 8 Regressions between wheat grain yield and the groundwater depth. GY, grain yield; GWD, groundwater depth. The equations represent the regressions between wheat grain yield and the groundwater depth. * , significant difference at P <0.05 probability level. studied how soil moisture and salinity were affected by the groundwater depth in the field of cotton in coastal saline soil. Interestingly, in our research, the average salinity contents under different treatments (Table 3) were higher than that of cotton fields (Zhang H et al . 2017). It is because the main growth stages for wheat are during spring and for cotton during summer, and the rainfall in spring (Fig. 1) was relatively lower than that of summer (Zhang H et al . 2017). Therefore, the salinity contents were substantially higher in spring for wheat (Table 3). On the other hand, SRMC and EC 1:5 showed a positive relationship in the wheat field of coastal saline soil (Fig. 4), which indicated that soil water and salt are closely inter-related. However, Zhang H et al . (2017) did not observe such a correlation. 4.2. Soil moisture and salinity affecting wheat growth and yield For this experiment in Y1, LA, SPAD reading, P n , the total aboveground biomass, grain yield, and flour quality were at their peak values in conditions for the groundwater depths of 1.9 m (standard soil moisture and medium salinity) and 2.3 m (slight drought and medium salinity) (Tables 3–5 and Figs. 5–7). Whereas, in Y2, higher results were observed under treatments of 2.2 m (slight drought and low salinity together) and 1.8 m (standard soil moisture and medium salinity combined) (Tables 3–5 and Figs. 5–7). However, Saqib et al . (2004) conducted a pot experiment to simulate soil water logging (water flooding for 21 days during wheat tillering and booting stages) and salt (NaCl, EC e , 15 dS m −1 ), and illustrated that wheat grain yield significantly decreased in the treatments of water logging, salinity, and waterlogged-saline as compared to the control (EC e , 2.6 dS m −1 ). In addition, the combined effects of soil water logging and salinity showed more adverse effects than the single effects of each treatment for just the MH-97 genotype (Saqib et al . 2004), and these results are similar to our results. Our study indicated that photosynthesis, grain yield, and flour quality of wheat were adversely influenced by water logging and high Table 6 Correlations between the groundwater depth and the leaf area per plant, the SPAD readings, the net photosynthetic rate ( P n ) 1) Item Growth stage Equation 2013–2014 2014–2015 Leaf area per plant Seedling y =–0.47 x 2 +1.86 x –0.86 R 2 =0.66 y =–0.38 x 2 +1.60 x –0.66 R 2 =0.62 Jointing y =–3.76 x 2 +15.06 x –7.12 R 2 =0.81 * y =–2.87 x 2 +12.11 x –4.72 R 2 =0.78 * Booting y =–7.11 x 2 +28.49 x –13.73 R 2 =0.82 * y =–4.92 x 2 +21.18 x –8.17 R 2 =0.80 * Filling y =–3.38 x 2 +13.73 x –4.09 R 2 =0.73 y =–2.90 x 2 +11.93 x –2.32 R 2 =0.72 Ripening y =–1.38 x 2 +5.49 x –2.85 R 2 =0.56 y =–1.05 x 2 +4.38 x –1.99 R 2 =0.53 SPAD reading Jointing y =–3.46 x 2 +13.71 x +33.98 R 2 =0.94 ** y =–3.06 x 2 +12.99 x +34.15 R 2 =0.89 * Booting y =–3.62 x 2 +14.69 x +34.02 R 2 =0.95 ** y =–3.13 x 2 +13.28 x +35.33 R 2 =0.84 * Filling y =–3.39 x 2 +13.66 x +33.29 R 2 =0.96 ** y =–3.02 x 2 +12.73 x +33.91 R 2 =0.83 * P n Jointing y =–4.76 x 2 +18.77 x +4.13 R 2 =0.86 * y =–3.22 x 2 +14.64 x +6.10 R 2 =0.75 Booting y =–4.97 x 2 +19.63 x +4.10 R 2 =0.83 * y =–3.29x 2 +14.84 x +7.03 R 2 =0.73 Filling y =–4.75 x 2 +18.72 x +3.51 R 2 =0.87 * y =–3.06 x 2 +14.13 x +5.95 R 2 =0.78 1) y stands for the leaf area per plant (cm 2 ), the SPAD readings, the P n (μmol CO 2 m –2 s –1 ) respectively; x represents the groundwater depth (m). n =6; df =3. * , significant difference at P <0.05 probability level; ** , significant difference at P <0.01 probability level.