What is a key difference between chemical fertilisers and manures in terms of nutrient release to plants?

The correct option is Manures release nutrients gradually.

Key Differences Between Chemical Fertilisers and Manures:

1. Nutrient Release Speed: Manures are organic materials derived from plant and animal wastes. They must be decomposed by soil microorganisms before their nutrients become available to plants. Consequently, manures release nutrients slowly and gradually over a longer period, providing a steady supply of nutrients and improving long-term soil fertility.

2. Chemical Fertilisers: Chemical fertilisers are commercially manufactured inorganic salts containing high concentrations of specific plant nutrients (such as nitrogen, phosphorus, and potassium). They are readily soluble in water and release nutrients quickly to plants, offering immediate nutrient availability rather than a gradual release.

3. Impact on Soil Structure and Biological Activity: Manures enrich the soil with organic matter, improving soil structure, water retention, and microbial activity. In contrast, excessive use of chemical fertilisers can diminish soil microbial activity and harm overall soil health over time.

Therefore, a key difference is that manures release nutrients gradually.