Which form of nitrogenlous fertiliser will be preferred for paddy and potato?

An ammoniacal form of nitrogenous fertilizer will be preferred for paddy and potatoes. Nitrogen requirements of rice crops are met from both the soil and fertilizers. The main form of nitrogen taken up by rice roots is ammonium in flooded paddy soil.
Potatoes can utilize nitrate, ammonium and urea nitrogen. Urea must be converted to ammonium inside the plant with the aid of urease.