The top few inches of soil do most of the work. Topsoil holds the organic matter, nutrients, and biological activity that crops depend on. Lose it and the land's productivity drops sharply, often for decades.

Topsoil forms slowly. It builds as plant material decomposes and earthworms mix it into mineral soil. Depending on climate and management, an inch can take centuries to accumulate. Erosion can remove that inch in a single storm.

What threatens topsoil

• Water erosion on bare slopes
• Wind erosion on dry, exposed fields
• Repeated tillage breaking down structure
• Removal during construction or mining

Conservation practices protect it. Cover crops hold soil in place between cash crops. Reduced tillage keeps residue on the surface. Windbreaks slow the wind that lifts particles into the air. Each practice buys time for the slow process of soil formation.