newslang:

Iron sulphate is the deal for acidifying and adding iron, but it's hard to get for free. What you can get for free will be worth about what it costs.

Don Yellman, Great Falls, VA

Oak leaves and oak sawdust are good and OK, respectively, and often free. Oak or other hardwood bark is OK also and may be free at some sawmills. Pine needles and bark are OK and may be free in places.

Agricultural sulfur is pretty cheap though, and highly effective.

I've never heard of Urine being used to acidify soil, but some use it as a source of nitrogen because of the Urea in Urine.

Being that Urine should be sterile, you can spray away using one of those hose end sprayers, to dilute it, to give you plants some nitrogen to feed on.

Here's some info from Wiki:

Fertilizers

Urine has applications in gardening and agriculture as a fertilizer. Gardeners often recommend a dilution of 10-20 parts water to one of urine for application to pot plants and flower beds during the growing season; pure urine can chemically burn the roots of some species. Urine typically contains more than 50% of the nitrogen and phosphorus and potassium content of whole sewage, and is widely considered as good as or better than commercially-available chemical fertilisers or stabilised sludge from sewage plants. Urine is also used in composting to increase the nitrogen content of the mulch, accelerating the composting process and increasing its final nutrient values.

Urine is also being actively considered as a fertilizer for use in food-crop agriculture in developed countries. Studies into its feasibility and safety usually indicate that it is an acceptable alternative to chemical fertilisers and stabilised sludge. However, the technology to implement its use on a large scale has not been developed, and is considered too expensive. There are also concerns over its safety regarding the potential for transmitting infectious disease and refluxing xenobiotic compounds (associated with toilet-cleaning products and prescribed drugs expelled in urine) in the human food chain. Proponents of adopting urine for this use usually claim the risks to be negligible or acceptable, and point out that sewage causes more environmental problems when it is treated and disposed of compared with when it is used as a resource. Critics generally agree that more research is needed into how the resource is to be collected, processed and handled.

A few people use urine as a crop fertilizer. These include organic farming cooperatives and eco-villages where special urine-diverting toilets with collecting tanks are installed. Many of these also employ concepts such as greywater irrigation and the composting of fecal matter. Many are the subject on ongoing feasibility studies sanctioned by governments and private organisations. These people generally reject safety concerns over its use on food crops provided that it is used with common sense. For example, application to fruit trees is considered safer than to bushes and especially root crops. It is also considered sensible to cease application at a safe interval before harvesting. However, the use of urine for this purpose is even rarer than its use on ornamental gardens.

In developing countries, the application of pure urine to crops is also rare. However, whole, untreated sewage, termed night soil, is often applied to crops and is considered essential. It is worth noting that this practice is not new and has been applied, along with crop rotation schemes, for thousands of years.

In Japan, urine used to be sold to farmers who would process it into fertilizers.

OK, I pee on(well, actually, around) my trees - I live out in the country; probably couldn't get away with it on a small residential lot in the city. I figure they can utilize the N and other nutrients, as well as the additional water.
I would be somewhat afraid that blueberries, on the other hand, might be adversely affected by the salts in urine, if you used much of it on them, due to the difference in their root system, as compared to oaks/pecans.