Answer: Option C.
Use genetically altered crops that fix their own nitrogen.
Step-by-step explanation:
Nitrogen is an essential nutrient that boost plants growth. It is the building blocks of amino acids and major constituent of plant chlorophyii which is the green pigment use for photosynthesis to produce glucose in the presence of sunlight , carbondioxide and water.
For nitrogen to be fixed to the soil, there are some plants that can naturally fixed nitrogen to the soil. These plants are legumnous or cover crops that fixed nitrogen to the soil through their root nodules.
Examples include beans, soyabeans, peas,clover and vetch. The farmers should plant leguminous plants which can fix nitrogen to the soil with their roots.