The first sign of a phosphorus deficiency is a sudden growth stagnation. If the deficiency continues, a dark discolouration occurs at the older leaves. These leaves can be found at the bottom of the plant. Some plant varieties may show pale yellow or dark-blue green old leaves instead. This is due to the accumulation of carbohydrates. These plant varieties will also end up with veins that are purple at the bottom. Additionally, you can recognise a lack of phosphorus underground: root development will decrease.
How do you recognise a phosphorus deficiency?
- At first, a phosphorus deficiency will lead to a sudden growth stagnation.
- Next, you'll notice a dark green discolouration of the lower, older leaves. Red or purple colours may also appear.
- Root development will decrease.
- Leaf extension is reduced. The same goes for leaf surface and the amount of leaves.
- Shoot growth will decrease. Stalks become short and slender.
- The plant is less resistant to diseases.
- The quality of the yield is reduced.
What is the (possible) cause?
- Low phosphorus concentration in the soil or substrate.
- The substrate is too wet.
- The pH value of the soil or substrate is too low.
- The temperature in the soil or substrate is too low.
- A lack of oxygen in the soil can reduce the absorption of phosphorus.