Role of Phosphorus in Citrus Production
Phosphorus is a component of nucleic acids and lipids and is important in metabolism, energy transfer, and photosynthate transport during citrus production.
Phosphorus response
Soils low in phosphate need phosphorus applications, as trials with oranges and lemons in Brazil show. Phosphate uptake occurs throughout the growth period, after flowering and through late fruit maturity. Good availability is important during periods of active root growth e.g. springtime and in between vegetative flushes.
Phosphorus and yield
Work on satsumas in Turkey shows that rates of 0.57lb P2O5/tree provided optimum yields over a four year period. For mature trees, application timing is not critical. Fertilizer is usually applied at the beginning or the end of season. Regular application by fertigation can increase efficiency of P-uptake and ensure good utilization of other nutrients at the same time.
Phosphorus and juice content
Phosphorus has a positive effect on juice content of the fruit.
Phosphorus and peel thickness
Over supply of phosphorus can reduce peel thickness, as study with mandarins in India shows. Therefore it is important to maintain the right balance between N and P rates.
Phosphate effect at growth stages
| Stage | Phosphate effect |
| Flowering | Maintain long-term productivity |
| Post Harvest | Maintain long-term tree productivity |
See more on Citrus Growth Stages.
General guidelines for Phosphate application
While not needed in large quantities, the correct balance of phosphorus to other nutrients is critical in citrus production. It is particularly important during early tree growth on new groves. In the long term, regular P applications will maintain the yield and fruit quality of mature citrus trees. Good availability is important during periods of active root growth e.g. springtime and in between vegetative flushes.
Phosphorus deficiencies in Citrus
Phosphorus deficiency is rarely seen on mature citrus trees, but when it is, it can reduce flowering, resulting in poorer production and small fruit with reduced juice content. Deficient leaves turn bronze and are smaller than normal. Older leaves die at the margins and tips. Branches are weak, flowering is reduced and fruit is spongy and soft before ripening.
