Urine works to add nitrogen and trace minerals. Just be sure to dilute it enough--one part urine to 20 parts water or more. I usually take a leak in a five gallon bucket and fill the rest with water, let it sit for a day, and then apply it to my ornamentals. Easy and you can't beat the price. The other thing you can do, if you have access to lawn clippings, is soak the clippings in a five gallon bucket for a day or two (one part clippings to five parts water) and then strain the water out and use it to water plants.
Wood ash is a source of potash, not nitrogen, I believe. Plus, it can make the soil too alkaline, so go easy on that.