For nitrogen I generally use blood meal (13.0-2.0-0). It provides rapidly available nitrogen. Don't use TOO much however, otherwise you'll end up with lush green growth and few fruits!

Thanks, I'll give blood meal a try.

Urine.

Here is a link that might be useful: Don't flush it!

What kind of soil test did you have done? Home test kits cannot reliably test for N with any degree of accuracy.....even many professional labs do not test for N. It is the most mobile of any of the plant nutrients - leaches easily, volatizes readily and will vary widely based on season, soil temperature, time of day, recent rainfall and amount of organic matter in the soil. Virtually ALL tests will show N deficient.

If you've added OM to the garden, you may not need to add any additional N at all. Otherwise, blood meal or alfalfa meal are fasting acting organic sources; urea or ammonium sulfate are fast synthetic sources.

Just so you know soil ph lower than 6.5 will reduce availability of nitrogen to the plants.

Available Nitrogen depends on many things starting with soil temperature (which regulates that activity of the soil bacteria and fungi that feed your plants), to soil moisture, to how much organic matter the soil has. If the other major nutrients are in fair balance then the Nitrogen probably is also, although excess levels of any nitrient can also present problems. Excess Potash can interfere with a plants ability to properly use N and vice versa.
Most all commercial soil test reports usually recommend applying 2 pounds of Nitrogen per 1,000 square feet without even testing for N and if you seriously think about that that is not very much. If your soil has adequate levels of organic matter Nitrogen more than likely will not be a problem.

I use ammonium nitrate - at about 1/4 the recommended dose - and them pile on compost.

After the first jolt, the Nitrogen levels tend to stay up because of the slower contribution of the compost.

Composting the kitty litter helps too. That stuff is loaded with urea.

Nitrogen in the soil is ephemeral. It really cannot be tested with any accuracy and to rely on soil test results could be folly.