We are offering 99.8% pure, 2 lb diammonium phosphate. Diammonium phosphate (dap) is the most widely used phosphate fertilizer among growers today. When applied as plant food, it temporarily increases the soil ph, but over a long term the treated ground becomes more acidic than before upon nitrification of the ammonium. It is incompatible with alkaline chemicals because its ammonium ion is more likely to convert to ammonia in a high-ph environment. The average ph in solution is 7.58.