Ca: 180-200 ppm Mg: 40-50 ppm K: 210 ppm P: 50 ppm Ammonium-N: 15 ppm Nitrate-N: 165 ppm Fe: 3-5 ppm Mn: 0.5 ppm Cu: 0.1 ppm Zn: 0.1 ppm B: 0.5 ppm Mo: 0.05 ppm Use the best grade, highly soluble fertilizers of highest purity available. The optimum pH for lettuce is between 5.5 and 5.8. The EC of most lettuce formulations will be between 1.5 and 2.0 mS.