PureCal ammonium free calcium nitrate fertilizer 13-0-0 with 18% calcium 55lb. bag PureCal calcium nitrate fertilizer, 13-0-0 with 18% calcium. Highly pure, white, very fine crystals. Easily and totally soluble in water. This product consists of calcium nitrate with 25% water of crystallization. All nitrogen is in the nitrate form. It contains no ammonium (NH4) nitrogen. one gram in one gallon of water yields 34.32ppm nitrate nitrogen and 47.52ppm calcium.