Triple Super Phosphate – TSP TRIPLE SUPER PHOSPHATE – TSP TSP has the highest P content of dry fertilizers that don’t contain nitrogen (N). Over 90 percent of the total P in TSP is water soluble, so it becomes rapidly available for plant uptake. As soil moisture dissolves the granule, the concentrated soil solution becomes acidic. TSP also contains 15 percent calcium (Ca), providing an additional plant nutrient. A major use of TSP is in situations where several solid fertilizers are blended together for broadcasting on the soil surface or for application in a concentrated band beneath the surface. It’s also desirable for fertilization of leguminous crops, such as alfalfa or beans, where no additional N fertilization is needed to supplement biological N fixation.