Nutrient deficiency: Magnesium (Mg)

21 05 2010

Summary

Mg Deficiency

Magnesium is a vital element for humans, plants and animals. Among other things it is a building block for chlorophyll in plants so it is essential for photosynthesis and it also plays an important role in a number of metabolic processes. Magnesium compounds have been used since antiquity in medicine for heartburn, against poisoning and as a laxative. Magnesium powder is used on equipment for gymnastic exercises because it makes the hands rough and absorbs moisture. Magnesium is a very light, malleable, elastic metal with a silver-white sheen that burns with a blinding light in the air. It is one of the most common elements on earth and the earth’s crust contains approx. 2.09% magnesium, but only in compound form. Magnesium compounds are frequently found in seawater, salt deposits, water from salt lakes and in some mineral waters. It is also present in tap water and, together with calcium, is responsible for the hardness of water. Inorganic, magnesium fertilizers are prepared from the same salts as are used when preparing potassium fertilizers. When grown from seeds cannabis don’t need extra nutrients for the first two weeks.

  • There are no visible symptoms in the first 3 – 4 weeks, the plant continues to grow well, is dark green and looks healthy.
  • The deficiency symptoms first become visible in cannabis after 4 – 6 weeks when small, rust brown necrotic spots and/or cloud-like chlorosis appear under the flowering top on the middle-aged leaves. The color of the young leaves and the development of the flowers remains normal.
  • The size and number of the rust brown spots increases on the leaves while the chlorosis also spreads and becomes yellower.
  • The symptoms spread throughout the plant which will now look a sorry sight.
  • If it is a serious deficiency the young leaves will also become chlorotic and production will fall.

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