My access to professionally-prepared liquid fertilizer is very limited. However, I'd like to use a liquid fertilizer to fertilize seedlings in my shade house bags if I can. Currently, I simply sprinkle a little NPK on the top of each bag every two months or so and water it in. If I want to liquefy the fertilizer, what concentration should I use?
I have access to a general NPK formula 13-13-21, and also urea, cow manure and compost. My potting soil is a reasonably good loam. If I choose to go with a liquid fertilizer, what recipe might be good?