Safwat,

I wouldn't use anything with urea in it. Adding potassium nitrate won't get rid of the urea. Incidentally, does the Schultz formula that you are talking about have a calcium content? Calcium is sometimes referred to as a macronutrient because plants need quite a lot of it. Does the water that you are using have a calcium content?

There are over-the-counter soluble nutrient products that don't contain any urea. Two that I use are Peters Specialties African Violet Plant Food (I get it from Home Depot or my local garden supply nursery) and Better-Gro Orchid Plus (I get it from Lowes). However, neither of those contain any calcium, and the water I use contains very little calcium, so I supplement them with added calcium nitrate.

I am not doing hydroponics as such, but my seed-starting has evolved into soilless gardening because, in this short Maine growing season, I need to set out well advanced plants.

MM

I would like to share with you my successful experiments, to proof that we can use Schultz Liquid nutriens in Hydroponics if we modified it, to each gallon of water I added the folloewing nutrients:
28 drops of Schultz liquid fertilizer 10-15-10, one half teaspoon potassium nitrate, and one forth teaspoon magnesium sulphate(Epsom salt).
PH was adjusted to 6.2 and the Electrical conductivity was average 1.12 ms/cm.
I used 100% perlite in a passive wick Hydroponic module.
Plants after 6 weeks prooved success so far are: Black Simpsin leaf lettuce,Arugula, pepermint and collard.
I added plain water on daily basis to compensate any water evaporation and I changed the nutes compleatly every 15-20 days. I will be glad to have feed back and any suggestions.