In nutrient management, which nutrient is most commonly associated with groundwater pollution due to leaching?

The nutrient most commonly associated with groundwater pollution due to leaching is nitrogen. This is primarily because nitrogen fertilizers, particularly in forms such as nitrate, can easily dissolve in water and move through the soil. When rainfall or irrigation occurs, this dissolved nitrogen can leach below the root zone and enter the groundwater. This process is exacerbated in agricultural practices where nitrogen is heavily applied to enhance crop yields.

Unlike nitrogen, phosphorus typically binds to soil particles and does not leach as readily, making it less of a concern for groundwater pollution in this context. Potassium and sulfur are also less prone to leaching compared to nitrogen. Therefore, the high mobility of nitrogen in the soil-water system and its tendency to create elevated nitrate levels in groundwater highlights its significant role in groundwater pollution, making it the correct answer in this case.