this thread is about parasitic infections and others from certain types of food - a lot of your posts are seeing issues inaccurately in black and white. Flukes can be transmitted through unwashed veggies but raw and undercooked fish and meat is the main cause. You are diverting the argument unconstructively. While treated human waste has been used as fertilizer throughout history, it wasn't widely used in developed countries until much later due to concerns about sanitation and regulations. UV light treatment is primarily used for wastewater disinfection and didn't play a significant role in treating waste for agricultural purposes.
Composting can be a great way to recycle organic materials and add nutrients to the soil. Leaving plant roots in the ground can contribute to this process as they decompose. However, there are no "little round balls of natural nitrates" on roots. Plant nutrients are distributed throughout the root system.
Some plants, like potatoes and tomatoes, can harbor diseases that can spread to subsequent crops. It's generally recommended to remove and dispose of these plants instead of composting them.
The key takeaways are that composting utilizes natural processes to break down organic matter and release nutrients, and careful consideration should be given to the potential disease risks associated with certain plants.