$5.$ Evaluate the role of ammonium chloride as a nitrogen source in saline soils, including its effects on soil health, plant stress responses, and overall agricultural productivity in saline$-$prone areas.

$6.$ Discuss the significance of calcium in calcium ammonium nitrate fertilizers, particularly in terms of its contribution to soil cation exchange capacity, plant health, and mitigating the potential negative effects of high nitrogen application rates.