The researchers studied how adding sulfur and/or nickel affected the levels of nickel and manganese in the soil around wheat roots. They found that the pH of the soil near the roots was slightly different from the rest of the soil. Nickel and manganese were more soluble in the soil near the roots than in the rest of the soil. The levels of nickel and manganese in the plant parts were more influenced by the soil near the roots than the rest of the soil. This shows that the distribution of metals in the soil near the roots is more important for determining how much heavy metals are available to plants than how soluble they are in the rest of the soil.