Which of the following have the ability to store nutrients?

• A. Organic matter
• B. Clay
• C. Both organic matter and clay
• D. Sand

Answer: (C)

Nutrient storage in soil relies on surfaces that can attract and hold positively charged nutrient ions, making them available to plants over time. Organic matter and clay minerals both provide many adsorption and exchange sites that capture nutrients and release them as plants need them. Organic matter stores nutrients through complexing and exchange processes, binding cations and slowly releasing them back into the soil solution. Clay minerals, especially the common 2:1 clays, have negative charges on their layered structures that create a cation exchange capacity, grabbing nutrients like potassium, calcium, magnesium, and ammonium and releasing them gradually. Sand, by contrast, has limited surface area and low charge, so it holds far fewer nutrients. So, both organic matter and clay can store nutrients, contributing to the soil’s nutrient-holding capacity.