The effect of biochar on relative water content, ion leakage, chlorophyll, phosphorus and rhizosphere soil cadmium availability in two grape varieties in the exposure of cadmium stress

Soil and water pollution, especially pollution by heavy metals such as cadmium,, has been noticed in many modern urban and industrial societies. If heavy metals accumulate in the soil, the capacity of the soil to keep the metals decreases, as a result, they enter the product and their bioavailability increases. Today, the use of biochar is suggested as a healthy method to control heavy metal pollution in the soil.In this research, in order to investigate the concentration of cadmium metals in soil and leaves in the exposure of cadmium stress and using biochar to investigate some physiological indicators of leaves and also to investigate the level of soil composition in 2 varieties of grapes in Malayer city, grape cuttings in plastic pots It was cultivated in the research greenhouse of Malayer University and Faculty of Agriculture.

In this experiment, the effect of biochar on two grape varieties (white Soltana and perlet) was investigated in the face of 100 mg/kg cadmium stress. After applying cadmium stress and using biochar (3% by weight) in the tested pots, The soils of the rhizosphere area were collected after 2 months of applying stress, and the cadmium concentration was done in the form of 5-stage classification in the research laboratory of Malayer University and finally analyzed by atomic absorption device. Leaf samples were also collected after about 2 months of applying stress and biochar, and physiological indicators such as ion leakage, chlorophyll, phosphorus and relative water content were measured.
The data related to each treatment (three replications) were carefully recorded and analyzed using SPSS software. EXCEL software was used to draw graphs. Duncan's test was used at a significance level of 1%.

The results showed that cadmium stress decreased the amount of chlorophyll and the relative content of water and also increased the amount of ion leakage. It was also observed that the application of biochar in both grape varieties increased the relative content of water, chlorophyll and phosphorus and reduced the amount of ion leakage to some extent. In the chemical forms of the soil, the use of biochar caused the reduction of exchange and carbonate forms and the increase of organic, oxide and residual forms. Biochar changed the easily replaceable parts of cadmium to those that are less available. In the conditions of cadmium stress, the use of biochar in soil can play a very important role in plant indicators such as relative water content, ion leakage, chlorophyll and phosphorus.The application of biochar decreased the fraction of exchangeable and carbonated cadmium, while the forms bound to Fe-Mn oxide, organic form and residual fractions increased.It was observed that the availability of heavy metals in the soil was significantly reduced with the addition of biochar compared to the control. Biochar significantly reduced ion leakage in both grape cultivars compared to untreated soil. In the organic form, the white Soltana variety in the presence of biochar and stress of 100 mg/kg of cadmium in the soil (6.57) compared to the samples without the presence of biochar (3.39) had an increase of 48.40% in the average concentration of cadmium. In Perlet cultivar, the percentage of increase was 21.45%, all of which showed an increase in organic form in the presence of biochar.Cadmium in soil in exchangeable and carbonate forms decreased after biochar application.In the residual form, the White Soltana variety in the presence of biochar and stress of 100 mg/kg of cadmium in the soil (20.88) compared to samples without the presence of biochar (15.47) had an increase of 34.97% in the average concentration of cadmium. In Perlet cultivar, the percentage of increase was 30.34%, which all showed the increase of residual form in the presence of biochar. Our results showed that the application of biochar can reduce the availability and toxicity of cadmium.

According to the results of this research, the application of biochar in the soil can be considered as an efficient management solution to control cadmium in areas contaminated with this heavy metal and can cause positive changes in plant leaf indices.Changes in the concentration of cadmium in different soil forms of grape cultivars as a result of the use of grape trunk biochar show that the use of biochar is a good strategy to reduce the risks of transferring cadmium to humans and the environment in metal-contaminated soils.