What does residual soil NO3-N refer to?

Residual soil NO3-N refers specifically to the nitrate nitrogen that remains in the soil following the harvest of a crop. This concept is crucial for understanding nutrient management and soil fertility because it indicates the amount of nitrogen that is still available for subsequent crops or soil organisms after a given growing season.

In agricultural practices, measuring residual soil NO3-N is important for making informed decisions regarding future fertilization. If there is a significant amount of residual nitrate left in the soil, it may reduce the need for additional nitrogen applications, thereby potentially lowering costs and minimizing environmental impacts associated with excess fertilizer use.

The other choices pertain to different contexts of nitrogen management in crops: nitrate nitrogen applied during planting indicates the fresh input of nutrients; nitrate nitrogen absorbed by plants refers to the utilization aspect; and nitrate nitrogen lost through leaching addresses nutrient loss rather than availability in the soil. Understanding residual NO3-N helps in gauging the efficiency of nitrogen use and promoting sustainable practices in crop production.