Which nutrient is most likely to leach quickly?

• A. Phosphate
• B. Potassium
• C. Nitrate
• D. Calcium

Answer: (C)

Nutrient movement through soil is governed by how soluble a nutrient is and how strongly it is held by soil particles. Nitrate stands out because it’s an anion (NO3−) that does not bind to the negatively charged soil surfaces, so it stays dissolved and moves with percolating water. That makes it highly mobile and prone to leaching under rain or irrigation.

Phosphate tends to stick to soil minerals, especially iron and aluminum oxides and calcium, forming adsorbed or precipitated compounds that slow its downward movement. Potassium and calcium are cations that attach to negative exchange sites on clays and organic matter, so they are retained to some degree and leach more slowly than nitrate. In well-drained, coarse soils or after heavy rainfall, these cations can still be lost, but nitrate leaches the fastest due to its lack of soil binding and high solubility.

So, nitrate is the nutrient most likely to leach quickly.