Phosphorus deficiency

• Role in the plant: phosphorus (P) is a structural element (proteins, nucleic acids...) and provides energy for plant processes such as ion uptake and transport. An adequate supply of phosphorus is needed for good plant growth and tuber formation and a lack of phosphorus can reduce the number of tubers. This nutrient is not very mobile in the soil and deficiencies may occur even when soils are rich in phosphorus in the case of poor root systems or reduced nutrient uptake due to various factors such as bad soil structure, drought, low temperatures, or when diseases damage the root development. In soils with a high pH level (above 7,5-8), e.g. in some volcanic soils, the availability of phosphorus can be highly reduced, even when high amounts of fertilisers are present in the soil.

          Good phosphate nutrition is beneficial for the formation of thick and resistant skin on tubers as well as for starch quality (viscosity).

• Symptoms of deficiency: the deficiency is initially manifested by an elongation of the leaflets, sometimes accompanied by slight deformation of the leaf margins, followed by brownish spots and a dull, dark green appearance of the leaf blade (photos 1 and 2). Severe deficiencies can lead to stunted plants with thin stems and smaller upwards curling leaves.