$50.$ The efficiency of nitrogen utilization from applied fertilizer is a critical aspect of agricultural science. If a crop utilizes $40\%$ of the nitrogen from an applied urea fertilizer, and the farmer wishes to apply $50$ kg of nitrogen to his fields, how much urea should he apply, knowing urea contains $46\%$ nitrogen?

$-$ A$)108\mathrm{.}7$ kg

$-$ B$)200$ kg

$-$ C$)150$ kg

$-$ D$)250$ kg

$51.$ When ammonium nitrate $($NH$$NO$)$ is used as a fertilizer, it dissociates into NH$$ and NO$$ in the soil. What impact does this dissociation have on soil health and microbial activity?

$-$ A$)$ Increases soil acidity, potentially harming beneficial microbes

$-$ B$)$ Has no significant impact on soil or microbes

$-$ C$)$ Enhances soil alkalinity, beneficial for most crops

$-$ D$)$ Reduces soil fertility by binding with essential nutrients

$52.$ Considering the environmental impact of synthetic fertilizer production, which of the following is a primary concern associated with the Haber$-$Bosch process?

$-$ A$)$ It consumes a significant amount of bio$-$based resources.

$-$ B$)$ It leads to a decrease in soil organic matter.

$-$ C$)$ It is a major industrial consumer of hydrogen, leading to large CO$$ emissions.

$-$ D$)$ It produces a significant amount of agricultural waste.

$53.$ In the context of global phosphorus $($P$)$ cycling, the use of phosphate rock for fertilizer production has been identified as unsustainable due to which of the following reasons?

$-$ A$)$ Phosphate rock is evenly distributed across all continents, leading to geopolitical tensions.

$-$ B$)$ The high energy cost of extracting phosphorus from phosphate rock is not economically viable.

$-$ C$)$ Phosphate rock reserves are limited and are being depleted by current rates of consumption.

$-$ D$)$ Phosphorus from phosphate rock is not biologically available to plants.