A detrimental effect of bush burning is that it

Bush burning refers to the practice of deliberately setting fire to areas of vegetation, such as forests or grasslands. It is often done to clear land for agricultural purposes or to manage vegetation growth. However, bush burning can have detrimental effects on the environment.

The question asks us to identify one of the detrimental effects of bush burning. The correct option is "destroys soil organic matter." Soil organic matter refers to the decaying plant and animal material in the soil that provides nutrients for plants and helps improve soil structure. When bush burning occurs, the intense heat can destroy this organic matter, reducing the fertility of the soil.

Option B, "destroys weed seeds," may seem like a potential detrimental effect, but in reality, some weed seeds can be resistant to fire and may actually benefit from the nutrients released after burning. Therefore, it is not the most accurate answer.

Option C, "sterilizes the soil," is not entirely correct either. While bush burning can reduce the number of microorganisms in the soil, it does not completely sterilize it. Some microorganisms can survive or recolonize the soil after burning.

Option D, "adds potash to the soil," is also not the correct answer. Potash is a source of potassium, which is a nutrient that plants need for growth. While some nutrients may be released into the soil after burning, the destruction of organic matter outweighs any potential benefits.

In summary, the detrimental effect of bush burning is that it destroys soil organic matter, reducing the fertility of the soil. This makes it more difficult for plants to grow and can have long-term negative impacts on agricultural productivity.