Which fertilizer nutrient is most likely to leach through sandy soils and contaminate groundwater?

Nitrogen is the nutrient most likely to leach through sandy soils and contaminate groundwater due to its chemical properties and mobility in the soil. Sandy soils have large particles and low water-holding capacity, which allows water to move through them quickly. When nitrogen fertilizers are applied to plants, particularly in forms such as nitrate, they can easily be transported with water as it infiltrates the soil.

As rainfall occurs or irrigation is applied, the water can carry dissolved nitrates beyond the root zone of plants, where they can enter groundwater systems. The potential for groundwater contamination is significant, particularly in areas with sandy soils, because the rapid movement of water effectively decreases the time that nitrogen is held within the soil, making it more likely to leach away.

In contrast, phosphorus, potassium, and sulfur have different behaviors in sandy soils. Phosphorus tends to adsorb to soil particles and does not leach as readily, while potassium and sulfur, although they can leach, do so to a lesser extent compared to nitrogen. Thus, the properties of nitrogen make it the most susceptible to leaching in sandy soil conditions.