What are the visual signs of phosphorus deficiency?
Written by
Nguyen Minh
Reviewed by
Prof. Charles Hartman, Ph.D.Plants that are suffering from phosphorus deficiency show distinctive purple stems and discoloration of older leaves as the primary visual cues. Symptoms start with the older leaves, as plants generally re-allocate phosphorus for new growth. Stems that turn purple and leaf color changes can be accentuated by cool temperatures, especially below 60°F (15°C). Ensure that you check the lower leaves first when diagnosing phosphorus deficiency for early detection.
Stem Symptoms
- Purple or reddish discoloration starting at base
- Shortened internodes creating compact growth
- Structural weakness and reduced thickness
- Intensified coloring under cool temperatures
Leaf Symptoms
- Bluish-green darkening in early stages
- Purple undersides and marginal curling
- Premature drop starting from lowest leaves
- Necrotic spots in advanced deficiency
Growth Symptoms
- Height reduction up to 30%
- Delayed flowering by 7-14 days
- Poor fruit set and small produce
- Reduced tillering in cereal crops
When looking at root systems, deficiency symptoms are clearly evident. You will observe reduced branching and shorter primary roots. White roots that are normally healthy develop a brownish tinge as they deteriorate. Legumes do not form nodules under conditions of deficiency. Careful excavation is your best means of assessing root health and degeneration without damaging the plant.
The development of flowers and fruits is clearly adversely affected. Your plants flower later and set less fruit. Current fruits are small and irregular in shape. There is also poor seed development and low seed viability. These issues surrounding reproduction will directly impact your harvest yield.
Symptoms that affect the whole plant include stunted growth and lower tolerance to winter hardiness. For example, with stunted growth, a plant will reach only 50-70% of its expected size. With stunted growth, the plant will reduce its tolerance to diseases and pest attacks. Cool-season grasses exhibit a higher degree of sensitivity to phosphorus shortages, particularly during the establishment phase of growth.
Accurately diagnosing a plant disease requires contrasting symptoms among plant types. Corn may present with purple midribs, while tomatoes may show curling or wilting of leaves. Trees can exhibit premature defoliation. Always consider environmental triggers, including temperature, soil moisture, and soil conditions, before arriving at a diagnosis. Accurate pigeon-holing of what to call the damage can reduce confusion with other diseases or nutrient deficiencies.
Read the full article: Phosphorus Deficiency Plants: Signs and Solutions
