Phosphorus is important for early root and shoot development, providing energy for plant processes such as ion uptake and transport.
Phosphate and yield
At tuber initiation, an adequate supply of phosphorus ensures supplies of optimum numbers of tubers are formed. While potatoes are very responsive to phosphate fertilizer applications, the economic optimum rate is often very difficult to define. Rates will depend on soil type and soil test results. The example below is on Desiree potatoes, Wales.
Petiole phosphorus levels and yield
In trials with Russet Burbank potatoes in USA, tuber yield is increased by 500 lbs/acre for every extra day during which petiole phosphorus is maintained above 0.22%.
Foliar phosphorus and marketable tuber size
This trial in Prince Edward Island shows that YaraVita SOLATREL applied during bulking increased marketable tuber size.
Foliar phosphorus and yield
In addition, foliar phosphate, applied after tuber initiation, has been shown in England trials to have a positive effect on tuber yields by increasing tuber size. However, foliar phosphate is not a substitute for soil applied phosphate. Without adequate soil phosphate early season growth is sub-optimal.
Phosphorus and starch viscosity
Phosphate fertilizer use can influence starch quality. By increasing the tuber P content, the viscosity of the gelatinized starch is also increased and the gelatinization temperature decreased. As starch is commonly used as a thickening agent in food and other products, good phosphate nutrition can be of significant benefit.
General guidelines for phosphate application
Following tuber initiation, phosphorus is an essential component for starch synthesis, transport and storage.
Under situations of high phosphorus tie-up e.g. volcanic soils or low organic matter, low P, sandy soils, it is important that fertilizer-P is placed close to the seed piece.
Because phosphorus is relatively immobile in the soil, banding the fertilizer usually works better than broadcasting.
|Phosphorus at potato growth stages
||Early growth, shoot and root elongation
|Before tuber initiation hook stage
||Higher tuber set
||Higher tuber set
||Maintain tuber growth