Co-application of biochars and Piriformospora indica improved the quality of coastal saline soil and promoted the growth of forage

Abstract

Soil quality is defined as the ability of soil to maintain the soil environment and the biosphere. Due to the limitation of salt and alkali stress, soil quality can be reduced, which in turn affects agricultural production. Biochar is widely used in saline-alkali land improvement because of its special pore structure and strong ion exchange ability, while Piriformospora indica is widely used in saline-alkali land improvement because it can symbiose with plants and improve plant stress resistance. However, the synergistic effect of combined biochar application and inoculation of P. indica on the quality of saline-alkali soil and plant development is uncertain. Hence, we investigated the combined influences of biochar and P. indica on the soil physicochemical characteristics, as well as the growth and chlorophyll florescence of sorghum-sudangrass hybrids (Sorghum bicolor × Sorghum sudane) in our study. The results indicated that after applying biochar and P. indica together, there was a considerable drop in soil pH, conductivity, Na⁺, and Cl^- concentrations. Meanwhile, the soil organic matter (SOM), available phosphorus (AP), and alkaline hydrolyzable nitrogen (AN) increased by 151.81%, 50.84%, and 103.50%, respectively, when the Bamboo biochar was combined with 120 ml/pot of P. indica. Eventually, sorghum-sudangrass hybrid biomass, transpiration rate, and chlorophyll content increased by 111.69%, 204.98%, and 118.54%, respectively. According to our findings, using P. indica and biochar together can enhance soil quality and plant growth. The results also provide insights to enhance the quality of saline-alkali soils and the role of microorganisms in nutrient cycling.

Keywords: Piriformospora indica; biochar; forage; photosynthesis; saline-alkali soil.

Figure 1

Effect of combined application of biochar and P. indica on soil Ph (A), SOM (B), AP (C), AN (D), pH (E), EC (F), soluble Na⁺ (G), and soluble Cl⁻ contents (H). Duncan’s multiple range was used to indicate a significant difference at p < 0.05 for treatments (n = 3). Uppercase letters indicate significant differences between different biochar types at the same P. indica dose, whereas lowercase letters indicate significant differences between the same biochar types at different P. indica doses. *p < 0.05; **p < 0.01; ***p < 0.001; ns, no statistical significance. SWC, soil water content; SOM, soil organic matter; AP, available phosphorus; AN, alkaline hydrolyzable nitrogen; EC, electrical conductivity.

Figure 2

Colonization of sorghum–sudangrass hybrid roots by P. indica (magnification, ×100). Colonization rates of P. indica in different treatments.

Figure 3

Effect of combined application of biochar and P. indica on plant height (A), leaf number (B), biomass (C), Chl (D), Tr (E), and Pn (F). Duncan’s multiple range was used to indicate a significant difference at p < 0.05 for treatments (n = 3). Uppercase letters indicate significant differences between different biochar types at the same P. indica dose, whereas lowercase letters indicate significant differences between the same biochar types at different P. indica doses. *p < 0.05; **p < 0.01; ***p < 0.001; ns, no statistical significance. Chl, chlorophyll content; Pn, net photosynthetic rate; Tr, transpiration rate.

Figure 4

Correlations between soil properties and sorghum–sudangrass hybrids properties. The correlation was evaluated by Pearson correlation coefficient. Red indicates a negative correlation, and blue a positive correlation, and the strength of color reflects the strength of the correlation. *p < 0.05; **p < 0.01.

Figure 5

Direct and indirect effects of biochar and P. indica on growth and photosynthesis of sorghum–sudangrass hybrids, as well as the soil physicochemical properties and nutrient contents. Models satisfactorily fitted to our data, as suggested by the Chi-square (χ2), goodness of fit index (GFI) and root square mean error of approximation (RMSEA) values [χ2 = 21.114 (p =0.331), GFI = 0.901, RMSEA = 0.056]. Blue lines indicate positive effects, while red lines indicate negative effects. Non-significant effects are indicated by gray lines. The width of the arrows indicates the strength of the significant standardized path effect. *p < 0.05; **p < 0.01; ***p < 0.001. Chl, chlorophyll content; Pn, net photosynthetic rate; Tr, transpiration rate; EC, electrical conductivity; SWC, soil water content; SOM, soil organic matter.