To find the most up-to-date information, I recommend contacting the following resources:
* Your local County Agricultural Commissioner's Office: They are responsible for regulating agricultural practices in your area.
* California Department of Food and Agriculture (CDFA): They oversee agricultural regulations for the entire state.
* California Environmental Protection Agency (CalEPA): They regulate waste disposal and other environmental issues.
You can also search online for relevant regulations using keywords like "horse manure disposal California" or "agricultural waste disposal California".