| Summary: | Heavy metal pollution in agricultural soil is a serious problem, which threatens the environment and human safety. In this study, the effects of biochar (BC), activated carbon (AC), and nanocarbon (NC) on the growth of peach trees under chromium (Cr) stress were investigated through pot experiments. The experimental results showed that under Cr stress, BC, AC, and NC could increase the soil nutrient content and enhance the soil enzyme activity. Moreover, all carbon forms promoted the conversion of Cr speciation; decreased the content of exchangeable (EXE), carbonate-bound (CARB), and iron–manganese-oxide-bound (FeMnO) Cr in the soil; increased the organic-bound (Org) and precipitated (Pre) Cr content; and reduced Cr availability. After BC, AC, and NC treatment, the content of Org-Cr in the soil increased by 86.05%, 72.97%, and 65.02%; the content of EXE-Cr decreased by 75.30%, 75.33%, and 73.10% compared with the control under severe Cr treatment, respectively. Moreover, the accumulation of Cr in plants decreased by 29.70%, 22.07%, and 20.52%, respectively. At the same time, these three carbons reduced the accumulation of Cr in various parts of the peach tree, alleviated the oxidative damage caused by Cr stress, effectively protected the photosystem of the leaves, improved the photosynthetic capacity, and promoted the growth of the peach tree. Compared with the control, the dry matter accumulation increased by 20.81%, 9.54%, and 6.95% with BC, AC, and NC treatment under severe Cr treatment. Therefore, BC, AC, and NC can all effectively alleviate soil Cr toxicity, and BC has the best effect, which can be popularized in production.
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