Phosphorous is particularly important during the reproductive development of plants which for potatoes starts before a good root system has developed and at a time when soil temperatures may still be fairly low, thus limiting uptake of Phosphorous.
Phosphorous is easily tied up in the soil and becomes less available when soils are very wet or dry or at low temperatures.
Adequate levels of phosphorous need to be available during the early part of initiation to enable the plant to absorb it for good yields.
UK Nutrition low pH fertilisers can be produced in a range of formulations with or without micronutrients.
A typical formulation is 5-20-2 + S and would be used at 50-200 litres/ha