I was looking for natural fertilizer for Malawi and came across a Kenyan study if im not mistaken that had villagers peed into a storage tank just to explore the usability of urea as local fertilizer. There were some interesting findings but the thing was that urine was too strong to use directly as fertilizer. directly on plants would overfeed and burn the plants. They mixed it with 1:10 with water to get to a right mixture