$9.$ Examine the strategic importance of potassium in plant stress tolerance, particularly how potassium fertilizers like potassium chloride and potassium sulfate can be used to enhance drought resistance and disease resilience in crops.

$10.$ Critically assess the concept of fertilizer use efficiency $($FUE$)$ in the context of balanced fertilization, exploring strategies to maximize nutrient uptake by plants while minimizing losses through leaching, volatilization, and runoff, with a focus on innovative application techniques and timing.