Possibly an unpopular opinion, but organic fertilizer and chemical fertilizer serve two different roles, and you should be using both.
Organic “fertilizer” (manure, compost, wood chips, really organic matter) is probably the only time and effort efficient way to increase your soil organic matter. That higher level of organic matter (referred to as humus, although it’s debatable if “humus” actually exists per se) is beneficial in a bunch of different ways, from higher microbial activity to better soil characteristics.
What organic fertilizer is not good at, is providing a steady quantity of free nutrients, in the correct ratios, with sufficient and balanced micro nutrients, at a high rate. Organic fertilizer does provide some readily available nutrients, and if you add a lot then it can provide a lot, but the NPK levels are always fairly low, and never balanced, and micronutrients are always extremely unbalanced. Sure, if you dose your plants weekly with a very careful blend of fish and bone meals, powdered kelp, a mixture of manures of known age, rock dust, Epson salt, and about a dozen other ingredients, all measured and calibrated, then you will achieve the same nutrient loading as using a water soluble commercial fertilizer, for about ten times the effort and a hundred times the cost.
Organic matter builds the soil, increase microbial activity, decreases certain diseases, and increases soil chemical buffering, drainage, and water retention. That’s what it does, that’s what it’s for, that’s how you should use it. Organic matter builds the soil. Fertilizer, on the other hand, provides unnaturally large quantities of the nutrients your plants need in the correct ratios (even if you are using natural fertilizers, the amount your garden gets is way, way more than that happens in nature. Buffalo don’t apply an even three inches of manure over the entire prairie every two months, but you do that and more to your garden. Gardening isn’t natural, and it isn’t supposed to be.). Fertilizer builds the plants.
Given all of that, when looking for cheap, bulk, balanced organic fertilizer, it makes the most sense to keep in mind that “balanced” and “fertilizer” are at odds with “cheap, bulk, organic (matter).” Remember, organic matter and fertilizer are two different things that have different garden roles. So, pick one and go for it, don’t try to please two masters at the same time. If you want balanced organic fertilizers, take out a bank loan and go buy the fancy bags of ground fish guts and burnt pig bones at Lowe’s. If you just want organic fertilizer, dump some horse poop on your garden, but remember that it’s not even close to balanced, so you’re going to need to buy the fancy stuff from Lowe’s anyway. Or… ditch the “balanced fertilizer” part, and find whatever “cheap, bulk, organic matter” is readily available.
For me, the local county waste dump and recycling center has piles of chipped up yard waste from the city that they give out at very low cost or free, and there are several horse boarding barns around that also sell their used beddings for cheap. That’s where I get my cheap, bulk, organic matter. Chipdrop is a popular service that provides loads of woodchips as well, but I’ve not had to use them. Actual farmers are unlikely to give you some of their waste, mostly for legal reasons and scale, but you could try your luck. Similarly, coffee places do have used grounds that they might give you, but the time it takes just to get those grounds isn’t worth the measly few pounds you’ll get, to my mind anyway. And, for similar reasons, using fresh, untreated human waste as fertilizer really isn’t worth the health hazards for the tiny bit of N and basically nothing else it contains.
As for fertilizers, I use a combination of generic slow release stuff (the cheapest Walmart 10-10-10 I can find) and a balanced water-soluble fertilizer that is sold as a “greenhouse fertilizer.” I also spot fertilize with custom applications of other fertilizers on an as-needed basis, which I get as big bags of super phosphate, iron chelate, magnesium salts, lime, sulfur, etc from the county farm depot. That water-soluble fertilizer is very cheap for what it contains (which is everything, even trace minerals), and, like the big bags of individual fertilizers, is easy to find at any of the local warehouses and agricultural depots. Don’t buy anything branded or marketed (Miracle-Grow, Organic, or whatever) unless the branding/marketing makes you feel better than other people, and don’t buy specialized fertilizer at a place with a customer service desk–buy it where the farmers buy theirs.
In short, be pragmatic: after a few months or a year, organic matter is organic matter, just use whatever is the easier and cheapest source, and fertilizer is fertilizer, regardless of if it was made from sun-dried organic kelp or made in a factory, so just focus on what is well-balanced and affordable.
Growing a $100 worth of berries with $10 of chemical fertilizer and cheap organic matter yourself does you and the world more good than growing $10 worth of berries with $100 worth of organic fertilizer, and a heck of a lot more than buying $110 worth of berries grown either way.
