Copper is important for plants, but too much can harm soil. Scientists studied how different forms of copper in soil changed over 5 years. They added copper to soil and grew crops to see what happened. In clean soil, copper levels stayed the same, but in polluted soil, they increased a lot. The type of copper that plants can use decreased over time in polluted soil. Dry conditions can change where copper is in soil. In clean soil, most copper is not harmful, but in polluted soil, more copper is in forms that can harm plants. This study shows that over time, harmful copper in soil can decrease, making it safer for plants.