Just use the toilet glitch. Build a toilet and supply it with a water source. Use it when your constipation is full (your hunger bar changes color). After you’ve done your business, hop off the toilet, flush and you’ll get a fertilizer. But your constipation won’t go away. Hop back on the toilet and repeat. Unlimited fertilizer.
I just tamed about 8 dung beetles and about 3 phiomias and then lvled food into the piggies and the bettles into weight. I have had these beetles for just 3 irl days and already have almost 1k fertilizer. 10/10 would recommend doing what I did