Native phosphorus compounds are highly insoluble and mostly unavailable for plant use. Phosphorus is most available in the pH range of 6 to 7. Deficiency Symptoms Ubiquitous requirement for so many metabolic processes generates deficiency symptoms uniformly throughout the plant. Purple veins result from development of anthocyanin pigments caused by an accumulation of sugars. Sometimes a uniform ashy green color.
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.