Crop plants are often grown in glasshouses where farmers carefully control environmental factors to maximize crop yield.
Explain how the following practices can increase crop yield:
Elevating the carbon dioxide (CO2\text{CO}_2CO2) concentration inside the glasshouse.
Adding a fertilizer containing magnesium ions to the soil.
Farmers must also protect their crops against pests.
Describe one example of using biological control to manage a crop pest.
State three advantages of biological control compared to using chemical pesticides.
