Why is the injection of UAN solution into the soil superior to dribbling on the soil surface?

Injecting UAN (urea-ammonium nitrate) solution into the soil is considered superior to applying it on the surface because it minimizes volatilization losses. When UAN is dribbled on the surface, especially in warm, dry conditions, a significant portion of the ammonia can volatilize into the atmosphere, reducing the amount of nitrogen that plants can uptake. By injecting the solution into the soil, it is more effectively retained in the root zone where plants can access it, thus enhancing its efficiency as a fertilizer. This method also protects the nitrogen from potential losses to the atmosphere and ensures that nutrients remain available for uptake by crops, leading to improved nutrient use efficiency.

The other options do not apply as strongly to the process of injection compared to the benefits related to minimizing volatilization losses. For example, while there may be some benefits to soil temperature and microbial activity in a broader context, these factors are not the primary reasons for the superiority of injection over surface application in reducing nutrient loss.