What are the three main factors identified as impairments to water quality from agriculture?

• A. Sedimentation from erosion, phosphorus, and nitrogen.
• B. Pesticide residues, salinity, and heavy metals.
• C. Algal blooms, turbidity, and dissolved oxygen.
• D. Nitrates, ammonia, and methane emissions.

Answer: (A)

When looking at how farming affects water, the most widespread impairments come from soil being eroded into waterways and from nutrients entering water bodies. Sedimentation from erosion adds solid particles to streams and lakes, making the water murkier, reducing light for aquatic plants, and harming habitats and fish. Phosphorus, often coming from fertilizer and manure, is a key nutrient that drives excessive plant and algal growth in many freshwater systems; as blooms develop and then decay, oxygen in the water can become depleted, stressing or killing aquatic life. Nitrogen, in forms like nitrates and ammonia, also fuels nutrient pollution and contributes to algal blooms and low-oxygen conditions, further degrading water quality.

Other issues like pesticide residues, salinity, or heavy metals can be concerns in some contexts, and algal blooms or low dissolved oxygen describe the effects you might observe, but the trio of sedimentation from erosion, phosphorus, and nitrogen best captures the primary, broad impairments agricultural activities commonly cause to water quality.