Explain the role of fertilizers in farming and perform calculations related to crop productivity. Identify natural fertilizers from provided data.

Farmers need to use fertilizers to replenish essential mineral nutrients (such as nitrates, phosphates, and potassium ions) in the soil that are absorbed by crops. This ensures that plants have sufficient nutrients for healthy growth, leading to increased crop yields and improved productivity, especially in intensively farmed areas.

The natural fertilizers listed in the diagram are Manure and Bone meal.

The use of fertilizers can have detrimental effects, primarily through eutrophication and groundwater contamination.

• Eutrophication: Excess fertilizers, particularly nitrates and phosphates, can be washed off fields into rivers and lakes through runoff or leaching. This influx of nutrients causes rapid growth of algae, known as an algal bloom. When these algae die, decomposer bacteria break them down, consuming large amounts of dissolved oxygen in the water. This oxygen depletion can lead to the death of fish and other aquatic organisms.
• Groundwater contamination: Soluble nitrates from fertilizers can leach through the soil and contaminate groundwater. High concentrations of nitrates in drinking water can be harmful to human health, especially for infants, potentially causing methaemoglobinaemia (blue baby syndrome).