If a soil is described as sandy and low in organic matter with shallow groundwater, it is most associated with what?

• A. Increased leaching risk
• B. Reduced leaching risk
• C. No effect on leaching
• D. Leaching will stop

Answer: (A)

Leaching risk is driven by how fast water moves through soil and how well nutrients are retained or transformed in that soil. Sandy soil has large pore spaces and drains quickly, so water percolates downward fast and soluble nutrients can be washed away. Low organic matter compounds this by offering little structure to hold water and fewer microbes to immobilize or transform nutrients, meaning nutrients stay in forms that can be easily leached. When groundwater is shallow, the leached nutrients don’t have far to travel before reaching the water table, increasing the chance of groundwater contamination. Put together, these factors create a situation where nutrients are moved downward readily, so leaching risk is higher. If organic matter were higher or the soil texture were finer, more water would be held and nutrients would be retained longer, reducing leaching risk; a deeper groundwater table would also provide more distance for attenuation.