New leaves emerging from the whorl are usually green, but may turn purple shortly thereafter. Phosphorus deficiency symptoms often occur as young plants are exposed to good growing conditions following cool and often wet conditions. This results in a lag phase where vegetative growth exceeds the roots' ability to supply phosphorus. Young plants are especially vulnerable because their root systems are small and phosphorus is immobile in the soil solution. Any cultural or environmental factors that limit root growth will aggravate deficiency symptoms.
Acidic soil can also intensify phosphorus deficiency symptoms.
Plants normally recover when favorable growing conditions allow root expansion. Phosphorus deficiency, however, will likely reduce yield by delaying maturity, decreasing root and stalk development, and reducing energy transfer and storage. Treatment options to quickly remedy phosphorus deficiency have limited effectiveness, because phosphorus is immobile in the soil solution. Surface application of phosphorus fertilizer will be tied up in the top couple inches of soil. Phosphorus injected as a sidedress treatment would increase availability to roots, however, you need to be careful not to prune roots.