In organic farming, certain substances are strictly prohibited to ensure the integrity and sustainability of the production process. Here are some common prohibited substances and practices in organic farming:

Synthetic Pesticides and Fertilizers
- Synthetic Pesticides: Conventional pesticides, including synthetic insecticides, herbicides, and fungicides, are generally prohibited. For example, substances like formaldehyde and arsenic are banned due to their toxic nature.
- Synthetic Fertilizers: Chemical fertilizers, such as synthetic nitrogen, phosphorus, and potassium compounds, are not allowed. Organic farming relies on natural fertilizers like compost, manure, and green manure.

Genetically Modified Organisms (GMOs)
- GMO Seeds and Products: The use of genetically modified seeds, organisms, and their derivatives is prohibited in organic farming. This ensures that organic chemistry products are free from genetically engineered materials.

Synthetic Growth Regulators and Hormones
- Growth Regulators: Synthetic growth regulators and hormones used to enhance plant growth or manipulate animal growth are not permitted. Organic farming emphasizes natural growth processes.

Prohibited Inputs in Organic Fertilizer Production
- Hazardous Waste Materials: Certain materials like fly ash, steel slag, and sludge are prohibited due to potential contamination risks.
- Invasive Species: Materials containing invasive species are also banned to prevent ecological damage.

Synthetic Processing Aids
- Processing Aids: In organic processing, certain synthetic aids like synthetic preservatives, artificial flavors, and colors are prohibited. Only natural and approved substances are allowed.

Specific Chemicals
- Strychnine and Arsenic: These natural toxic substances are prohibited due to their harmful effects on human health and the environment.
- Sodium Nitrate: This substance is not allowed as a soil amendment in any form.

Practices
- Antibiotic Use: Antibiotic therapy is prohibited in organic livestock farming. Vaccines, however, are allowed as a preventive measure against infectious diseases.
- Conventional Seed Treatment: Seeds treated with synthetic chemicals are not permitted. Organic seeds must be produced without the use of prohibited substances.

These prohibitions are in place to maintain the organic integrity of organic chemistry products and to promote sustainable agricultural practices that protect the environment and human health. Compliance with these standards is essential for obtaining organic certification.