All deficient plants exhibit stunted growth. Phosphorus Management Continued P applications builds up the soil P levels. Controlling erosion reduces P losses. Maintaning soil pH between 6 and 7 helps keep P in available forms. P fixation by soils can be reduced by fertilizing shortly before cropping as a concentrated band near the plant roots.
Rock phosphate is very slowly available at best.
Superphosphate is the result of treating rock phosphate with sulfuric acid. Triple superphosphate is the result of treating rock phosphate with phosphoric acid. K that would otherwise be available is often fixed between plates of expanding clays especially during dry periods. However, large amounts of it are in soil solution at any one time, and large amounts are lost by leaching. Large amounts of potassium are removed by crops.