Two types: "P.N." solution: to 25 gals, water add tablespoons of, Potassium phosphate (monobasic) 1; Potassium nitrate 4; Calcium nitrate 7; Magnesium sulfate (Epsom salts) 4; "T.C." solution: Ammonium phosphate (monobasic) 1; Potassium nitrate 5; Calcium nitrate 5; Magnesium sulfate 4; to both solutions add iron, boron, manganese, zinc and copper in minute quantities. White, Amer. orchid culture.(1939) 74; Logan and Cosper, Orchids.(1949) 125