There's a ton of reasons to consider Vegan amendments for your soil and fertilizer needs. For some, it's a life choice based on the food they put in their body, for others it may be a desire to not support the current meat industry and slaughterhouses. That's definitely something I can get behind.
Now just to be clear, I don't personally believe Veganic or Vegan-grown vegetables/cannabis to be inherently better than other methods of gardening. At the end of the day, the plant doesn't know if the nitrogen came from a plant or animal source. In a forest environment, you have animals constantly dying or leaving manure on the forest floor. You have earthworms and insects as well as microbes decomposing the organic matter. It's part of a natural process.
Regardless of the ethical or moral considerations, here's some great options for growers. You can click on any of the listed amendments to read more. Certain amendments like kelp meal or alfalfa meal have other benefits like naturally occurring plant growth hormones, making them more beneficial than just the nutrient content.
Below is some of the options for each of these macro and micro nutrients, along with the percentage they contain of that particular nutrient. Just click on any of the amendments for a link to more information.
Water (if your water source is 40-60 ppm or higher then you may not need to supplement Ca in your soil).
Wild Harvested Sources: Keep in mind these are fairly low in macro-nutrients and will vary based on the soils they are grown in.
Nettle, Comfrey, Horsetail, etc...
Beneficial but may not qualify as "Vegan"
Earthworm Castings - I've heard some Vegan growers say this is okay and some that won't use them. That being said, Earthworm castings are one of the BEST amendments to any soil. High levels of beneficial microbes along with plant-available nutrients.
Insect Frass (3-2-4) - Good ratio of macro-nutrients as well as excellent microbial content. One of my favorite all around fertilizers and sustainably grown.
Oly Mountain Fish Compost - A 2 year aged fish and woody material compost that contains excellent microbiology right out of the bag.
Sample Soil Recipe: (feel free to adjust to your own growing conditions or substitute other ingredients from the list)
1/3 Sphagnum Peat Moss or Coco Coir (if using Coco, add another 1/2 c. gypsum)
1/3 Compost or Earthworm Castings
1/3 Aeration (Pumice, Perlite, Vermiculite, Lava Rock, etc...)
add at 1 cup per cubic ft:
Neem Seed Meal
add at 1/2 cup per cubic ft:
Soft Rock Phosphate
add at 1/4 cup per cubic ft:
Ultimately it's best to get a soil test so you can see what your nutrient levels are, but as long as you plant looks happy then that's the ultimate test. Happy growing!