Fertilizers that you can find in walmart will say on the outside x-x-x (ex. 10-12-10) this is how much Nitrogen Phosphor and Potassium is in the fertilizer. You can also use organic nutrients too. If im not mistaken I believe urine is high in nitrogen
Nitrogen deficiency is best remedied with organic nutrients. Your local garden centre should carry a good lineup. I don't want to step on any toes here, but I personally don't recomend any growing products that Wal-Mart stocks. Chemical fertilizers produce some fairly carcinogenic by-products, and make your smoke taste funny even after flushing. Urine is a popular and effective remedy, but it is also the product of all the badness your body wants nothing to do with. Not very nice for your plant. Organics may be a problem if your growing hydro, but Advanced Nutrients and other major hydropic nutrient companies have a wide selection of products to meet every need, including nitrogen deficiency, and are all tailored to Cannabis growing. Sorry for the tedious post, hope this helps
Blood meal is my preferred method of adding nitrogen, the problem with urin is that it's to inconsistent/variable.