Rehabilitation of soils containing high salt levels with beneficial fungi

Abstract

Soil salinity not only reduces the quality of the soil, but also causes ionic imbalance in the plant, competition in the nutrient uptake and toxic effects at high concentration. Combating salinity, which has become a greater stress factor due to impact of drought and high temperatures, is of great importance. In this study, 3 kg soil in pots, adjusted to 12 mS/m EC, under four different treatments (3 different fungi species and control) were compared in a laboratory environment. The experiment was designed with three replications for each subject and one plant in each pot. Fungi species (Clononotachys rosea, Trichoderma sp., Taloromyces funiculosus) were used as soil inoculant to reduce soil salinity. The soil electrical conductivity (EC) was between 9.25 and 9.95 mS/m within 1 month in tomato cultivated soils, while the EC of the plant-free medium was between 10.4 and 11.4 mS/m: thus, the salt content did not differ statistically. EC values of the saline soils was decreased by 21-, 17-, 29 %, respectively, when Trichoderma sp., Taloromyces funiculosus, Clononotachys rosea were applied to tomato plant growing soils. These fungi also decreased the soil EC values by 15-, 16-, 25 %, respectively, in the plant-free environment. The chlorophyll SPAD value of tomato plants grown in saline soils decreased from 22.65 to 0, however, the SPAD values of tomato plants grown in soils with Clononotachys rosea, Trichoderma sp., Taloromyces funiculosus were increased from 22.4-, 25.6-, 24.1 to 29.3-, 50.2-, and 24.5. Similar findings were also observed for the increase in the chlorophyll content of the tomato plant. The fungi mentioned above also contributed to the increase of soil macro (Ca, Mg, K, P) and micro (Fe, Cu, Zn, Mn) element contents, and to the improvement of soil available phosphorus amount (P2O5) with the increase in soil phosphorus content. Fungi inocula induced a statistically significant increase of soil micronutrient concentrations (p>0.05). Sodium (Na) concentration in saline soils did not change in inoculated-non-inoculated soils. These findings were interpreted as fungi inocula were not able to assimilate the salt from the soil, but they instead contributed to the release of macro and micro elements that were unavailable under saline conditions, possibly due to their metabolic activities. According to the results of soil analysis at the end of the experiment, it was revealed that the pH value was 7.72 in the control pots and 3.28 in the pots treated with Taloromyces funiculosus, and the EC value was 12.34 and 9.74 mS/m, respectively. Among the fungi studied, Taloromyces funiculosus was found to be more effective than other two fungi on decreasing soil salinity and increasing micronutrient availability to plants.