More mature foliage fade to a yellow or light green hue closer to the edges of the leaf and on the veins. If the color of the bush resembles a photo, your plant is experiencing a magnesium deficiency. This problem should be resolved immediately, otherwise the painful process may go too far at a certain stage, and the plant will instantly lose a considerable portion of its foliage.
Magnesium is a mobile nutrient – in other words, inside the plant, it migrates from older leaves to young ones. That is why the first symptoms of its deficiency appear on the lower tiers of the plant.
The edges of the leaves sometimes not only change color, but also become brittle, which makes it possible to distinguish between magnesium deficiency and chemical burns . Sometimes, if the problem is started, the leaves become covered with a brown speck in the burnt areas, as well as along the edges of the leaves.
Solving the problem of magnesium deficiency
- First of all, you should check the soil pH at the roots – if it turns out to be too low, this may be the problem (especially in hydroponics). If the pH is really too low, prepare the water for abundant watering, make sure it is at the correct acidity of 6.2-7.0, and apply the usual dose of fertilizer.
- Cultivation in coconut fiber and / or irrigation with reverse osmosis water usually requires additional calcium and magnesium from the grower. Use drugs like Cal-Mag.
It should be borne in mind that the wrong pH will prevent the roots from absorbing additional magnesium in any case, so the task of checking the acidity of the soil at the plant roots remains the first priority. In addition, the introduction of excess magnesium threatens to block other elements.
- In soil, magnesium is best absorbed at a soil pH of 6.0 – 7.0;
- In hydroponics, the best acidity for magnesium is 6.0 – 6.5.
After solving the problem, the unnatural color stops spreading over the lower leaves after about a week. Affected foliage is unlikely to regain its original color.
Dolomite lime for growing in the ground
One way to prevent your plants from surviving magnesium deficiencies is to add dolomite lime (if the soil is organic) to the soil. Lime should be of the finest grind that can be found. Dolomite contains calcium and magnesium, its advantage is that this material tends to release substances to plants slowly, over several months. The pH of dolomite is neutral (7.0) and helps to maintain a constant level of acidity, favorable for cannabis.
How to mix dolomite flour correctly
For every 4-5 liters of soil or substrate, add 6-7 teaspoons of dolomite. Thoroughly mix dolomite with dry soil (substrate), then slightly moisten with water with a pH of 6.5 and let the resulting mixture stand for 1-2 days. Then check the acidity of the soil, and if it is in the range of 6.2-7.0, plant hemp. For outdoor cultivation, follow the instructions on the lime pack.
In some cases, magnesium deficiency is triggered by a lack of iron or calcium . A formulation such as Cal-Mag is recommended, especially when using highly filtered irrigation water, since the tap water usually contains sufficient amounts of magnesium, calcium, and iron.
Cal-Mag, in addition to calcium and magnesium, contains traces of iron, which may be useful.
After correcting the problem, monitor the condition of the plant. It is recommended not to cut off the affected leaves until you are sure that the bush is on the mend, because it will be on the diseased leaves that it will be noticeable first of all if this is not the case.