Starting your own compost is one option for cultivating your own high P fertilizer. Adding egg yolks, animal bones, fish waste, and anything that has a higher P ratio will increase the P ratio of the compost. When dealing with material prone to disease, it's best to use a high heat composting approach to sterilize the end product. There are various yard tumblers that make this rather easy.
Primary purchasable sources from (http://www.grow-it-organically.com/organic-phosphorus-fertilizers.html):
- Soft Rock Phosphate 0-18-0
- Bat Guano (High-P) 3-10-1
- Steamed Bone Meal 3-15-0
- Fish Bone Meal 3-18-0
- Rock Phosphate 0-33-0
- Rock Dust (Crushed Granite) 0—3-5—0, trace minerals
Additional composting sources for P:
Some food sources have pretty high levels of phosphorus naturally -
banana peels, crab shells, shrimp peelings, most grains and nuts - and
these should all be added to compost when available. Meats, poultry,
eggs and dairy products are also phosphorus-rich, but you'd want to
avoid adding those to your compost. (source)
The reason they mention avoiding the disease prone materials is because there isn't necessarily an easy way to verify that the end product is indeed disease-free. A heat thermometer should be enough to confirm that the center is at least cooking adequately however you will need to be sure that the entirety of the batch is mixed and turned so that every bit of it is cooked.
Since you can't use animal products or fish emulsion (do however note the above paragraph on compost heat-sterilizing), and you don't want to spend more on shipping, your left with:
- banana peels
- most grains and nuts
Extended looser definition of animal products would additionally include:
- egg shells
- crab shells
- shrimp peelings
- bat guano
- fish bone meal