Necessary for seed germination, photosynthesis, protein formation and almost all aspects of growth and metabolism in plants. It is essential for flower and fruit formation. P is a constituent of energy-transfer compounds such as NADP and ATP, and molecular complexes such as the genes. The energy compounds are necessary for photosynthesis, respiration, and synthesis of biomolecules. Cannabis takes up large amounts of P during germination and seedling stages. During flowering and seed set, Cannabis' need for phosphorous is also high.
Deficiency symptoms: Growth is stunted and old leaves initially dark green; older leaves may turn purple. Leaves overall are smaller and dark green; red colour appears in petioles and stems. The leaves may also develop red or purple colour starting on the veins of the underside of the leaf. Generally the tips of most of the leaf blades on the lower portion of the plant die before the leaves lose colour. Lower leaves slowly turn yellow before they die. Very acidic conditions can dramatically decrease P availability.
High P in the plant can cause Fe and Zn deficiencies. High P levels in the soil can help to deter aluminum toxicity in very acidic conditions.
Benefit: Phosphorus does a lot of things for the plant. One of the most important parts of Phosphorus is: It aids in root growth and influences the vigour of the plant and is one of the most important elements in flowering as well helps to germinate seedlings.
Phosphorus is an essential plant nutrient, and since it is needed in large amounts, it is classified as a macronutrient. Phosphorus is a MAJOR important nutrient in the plants reproductive stages. Without this element the plants will have a lot of problems blooming without proper levels of Phosphorus.
When your plants are deficient in phosphorus, this can overall reduce the size of your plants. Not enough causes slow growth and causes the plant to become weak, to little amount of Phosphorus causes slow growths in leaves that may or may not drop off. The edges all around the leaves or half of the leaves can be brownish and work its way inwards a bit causing the part of the leaves to curl up in the air a bit. Fan leaves will show dark greenish/purplish and yellowish tones along with a dullish blue colour to them.
Sometimes the stems can be red, along with red petioles that can happen when having a Phosphorus deficiency. This isnʼt a sure sure sign of you having one though, but can be a sign. Some strains just show the red petioles and stems from its genes. So pretty much the overall dark green colour with a purple, red, or blue tint to the fan leaves is a good sign of a Phosphorus deficiency.
Having Cold weather (below 50F/10C) can make phosphorous absorption very troublesome for plants.
Many people get a Phosphorus deficiency confused with a fungus problem because the ends of the leaves look like a fungus problem, But the damage occurs at the end of the leaves. side of the leaves and has a glass like feeling to it as if it had a ph problem.
Parts affected by a phosphorus deficiency are: Older Leaves, Whole plant, Petioles.
Too much Phosphorus levels affect plant growth by suppressing the uptake of: Iron, potassium and Zinc, potentially causing deficiency symptoms of these nutrients to occur def in plants. A Zinc deficiency is most common under excessive phosphorus conditions, As well as causing other nutrients to have absorption troubles like zinc and copper. Phosphorus fluctuates when concentrated and
combined with calcium Problems with Phosphorus being locked out by PH troubles Cold wet soils, acid or very alkaline soils, compacted soil.