Which statement best describes a set of amendments commonly used to improve drainage in heavy soils?

• A. Organic matter and lime
• B. Clay, silt
• C. Organic matter (compost), coarse sand, and gypsum
• D. Vermiculite and peat

Answer: (C)

Heavy soils drain slowly because dense clay particles pack tightly and trap water, leaving little space for air. To improve drainage, you want to change the soil structure to create larger, connected pore spaces. Organic matter, like compost, helps by loosening the soil and forming stable aggregates that increase porosity and infiltration. Adding coarse sand introduces larger particles that, when well integrated, create macropores for quicker water movement. Gypsum provides calcium that can help clay particles flocculate (clump together) rather than disperse, which strengthens soil structure and opens up the pore network, especially in soils with sodium on the clays. Together, these amendments address both the physical structure and the chemistry of heavy soils to improve drainage. The other options either don’t target drainage specifically or include amendments that don’t promote better drainage as effectively.