Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

leaching or vaporizing from the pressboards and other building materials. Such pollution causes plant growth to slow to a crawl.
Hot soil: Soil over 90°F (32°C) will harm the roots. Often, outdoor soil that is used in the containers warms up to well over 100°F (38°C).
Roots receiving light: Roots turn green if the light shines through the container or the hydroponic system. Roots require a dark environment. Their function slows substantially when they turn green.
----
     
Nutrients
    Nutrients are elements that the plant needs to live. Carbon, hydrogen, and oxygen are absorbed from the air and the water. The rest of the elements, called nutrients, are absorbed from the growing medium and nutrient solution. Supplemental nutrients supplied in the form of a fertilizer allow marijuana to reach its maximum potential. Nutrients are grouped into three categories: macronutrients or primary nutrients, secondary nutrients, and micronutrients or trace elements. Each nutrient in the above categories can be further classified as either mobile or immobile.

     
----
    I would like to thank the scientists at CANNA Research, Breda, Netherlands for information about nutrient deficiencies and toxicities in cannabis. The research team at Canna has been experimenting with cannabis in their fully-equipped scientific laboratory for 20 years. Mauk, head scientist, has made numerous discoveries, and proven them scientifically, about the nutritional needs of the cannabis plant. Hit their web site at
    www.canna.com
----
     
    Mobile nutrients-nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and zinc (Zn)-are able to translocate, move from one portion of the plant to another as needed. For example, nitrogen accumulated in older leaves translocates to younger leaves to solve a deficiency. The result, deficiency symptoms appear on the older, lower leaves first.
    Immobile nutrients-calcium (Ca), boron (B), chlorine (Cl), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), silicon (Si) and sulfur (S)-do not translocate to new growing areas as needed. They remain deposited in their original place in older leaves. This is the reason deficiency symptoms appear first in the upper, new leaves on top of the plant.
    Mobile nutrients translocate within a plant. They move to the specific part of the plant where they are needed; this causes the older leaves to show deficiencies first.

Macronutrients
Nitrogen (N) - mobile
    Practical Information: Marijuana loves nitrogen and requires high levels of it during vegetative growth but lower levels during the balance of life. Nitrogen is easily washed away and must be replaced regularly, especially during vegetative growth. Excess levels of nitrogen in harvested plants cause the dried marijuana to burn poorly.
    Technical Information: Nitrogen regulates the cannabis plant’s ability to make proteins essential for new protoplasm in the cells. Electrically charged nitrogen allows the plant to tie proteins, hormones, chlorophyll, vitamins, and enzymes together. Nitrogen is essential for the production of amino acids, enzymes, nucleic acids, and chlorophyll and alkaloids. This important nutrient is mainly responsiblefor leaf and stem growth, as well as overall size and vigor. Nitrogen is most active in young buds, shoots, and leaves. Ammonium (NH 4 +) is the most readily available form of nitrogen. Be careful when using too much of this form; it can burn the plants. Nitrate (NO 3 -)-the nitrate form of nitrogen-is much slower to assimilate than ammonium. Hydroponic fertilizers use this slower-acting nitrogen compound and mix it with ammonium.
    Deficiency: Nitrogen is the most common nutrient deficiency. The symptoms include slow growth. Lower leaves cannot produce chlorophyll and become yellow between the veins while the veins remain green. Yellowing progresses through the entire leaf, eventually causing it to die and drop off. Stems and the leaves’ undersides may turn reddish-purple, but this can also be a sign of a phosphorus deficiency. Nitrogen is very mobile, and it dissipates into the environment quickly. It must be added regularly to sustain fast-growing gardens.
    Progression of deficiency symptoms at a glance:
    Older leaves yellow between the veins (interveinal chlorosis).
    Older bottom leaves turn entirely yellow.
    More and more leaves yellow. Severely affected leaves drop.
    Leaves might develop reddish-purple stems and veins on leaf undersides.
    Progressively younger leaves