Many homeowners regularly add commercial fertilizers to their lawns and gardens to maintain a healthy balance of nutrients in soil. The widely available commercial fertilizers contain only macronutrients—namely, nitrogen, phosphorus, and potassium. To remain healthy in the long term, soil for lawns requires the presence of these macronutrients and also trace amounts of micronutrients such as zinc, iron, and copper, which are depleted when grass clippings are raked up rather than allowed to decay and return to the soil.

Which one of the following can be properly inferred from the statements above?