Question

For what purpose do farmers add $\mathrm{CaO}$ (lime) and ${\mathrm{NH}}_4{\mathrm{NO}}_3$ to their felids? Why are they never added together?

Answer 1

Part 1: Addition of Calcium oxide to fields

• Plants grow best when the pH of the soil is near 7.
• When soil becomes very acidic or excessively basic, it is no longer appropriate for many crops and plants. Most crops, fruits, and grass require a pH of 6 to 7.
• A soil pH approaching 7 is referred to as sweet.
• When soil becomes excessively acidic, it is neutralized by adding some base to it, and the objective is completed by adding Calcium oxide $\left(\mathrm{CaO}\right)$ to it.
• Calcium oxide when mixed with water gives Calcium hydroxide, which is alkaline in nature and helps the pH value of the soil to increase and process is known as sweetening of soil.

Part 2: Why Calcium oxide and ammonium nitrate not added together

• Whereas, the solution of Ammonium nitrate(${\mathrm{NH}}_4{\mathrm{NO}}_3$) is acidic in nature, as it is a salt of a strong Nitric acid and a weak base, which is Ammonium hydroxide. It helps make highly basic soil to acidic.
• So, these two can't be added together because they both are of different nature and hence will nullify each other defying the entire purpose.