Harmful substance present in Urea is
Urea when heated to a temperature above 140 -170 , form biuret by joining of two urea molecules 2CO(NH2)2 NH2CONHCONH2 + NH3 In urea biuret should not be >1.5 % (as per Fertilizer Control Order of Government of India) Biuret content should not exceed >0.25 % for foliar spray
