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

fertilizers like BioCanna, Earth Juice, or Fox Farm, you will need to try different feeding amounts and schedules to get the exact combination to grow top-quality bud.
    Taking an accurate EC reading or mixing the exact amount of a specific nutrient is very difficult in organic hydroponics. Chemical fertilizers are easy to measure out and apply. It is easy to give plants the specific amount of fertilizer they need in each stage of growth.
    Organic nutrients have a complex structure, and measuring content is difficult. Organics are difficult to keep stable, too. Some manufacturers, including BioCanna, Earth Juice, and Fox Farm, have managed to stabilize their fertilizers. When buying organic nutrients, always buy from the same supplier, and find out as much as possible about the source from which the fertilizers were derived.
    Combine premixed soluble organic fertilizers with other organic ingredients to make your own blend. Growers experiment to find the perfect mix for their system and the varieties they are growing. Adding too much fertilizer can toxify soil and bind up nutrients, making them unavailable. Foliage and roots burn when the condition is severe.
    Soluble organic fertilizers are fairly easy to flush from the growing medium. Like chemical fertilizers,organic fertilizers build to toxic levels easily. Look for the same symptoms as in soil–burned leaf tips, discolored misshapen leaves, brittle leaves, etc. Organic nutrients require heavier flushing. Rinse medium with three gallons of water for every gallon of medium. Some growers flush with plain water the last two weeks of flowering to get all fertilizer taste out of buds.
    Mix seaweed with macronutrients and secondary nutrients to make a hydro-organic fertilizer. The amount of primary and secondary nutrients is not as important as the menagerie of trace elements that are in an available form in the seaweed. Major nutrients can be applied via soluble fish emulsion for nitrogen; phosphorous and potassium are supplied by bat guano, bone meal, and manures. More and more organic growers are adding growth stimulators such as humic acid, trichoderma bacteria, and hormones.
Reservoirs
    Nutrient solution reservoirs should be as big as possible and have a lid to lessen evaporation. Gardens use from 5-25 percent of the nutrient solution every day. A big volume of nutrient solution will minimize nutrient imbalances. When the water is used, the concentration of elements in the solution increases; there is less water in the solution and nearly the same amount of nutrients. Add water as soon as the solution level drops. The reservoir should contain at least 25 percent more nutrient solution than it takes to fill the beds to compensate for daily use and evaporation. The greater the volume of nutrient solution, the more forgiving the system and the easier it is to control. Forgetting to replenish the water supply and/or nutrient solution could result in crop failure.
    Check the level of the reservoir daily, and replenish if necessary. A reservoir that loses more than 20 percent of its volume daily can be topped off with pure or low (500 ppm) EC water. Sophisticated systems have a float valve that controls the level of water in the reservoir.
    If your reservoir does not have graduated measurements to denote liquid volume, use an indelible marker to make a full line and the number of gallons or liters contained at that point on the inside of the reservoir tank. Use this volume measure when mixing nutrients.
    The pump should be set up to lift the solution out of the reservoir. Set reservoirs high enough so spent nutrient solution can be siphoned or gravity-flow into a drain or the outdoor garden.
Reservoir Temperature
    The temperature of the nutrient solution should stay between 60-75°F (15-24°C). However, nutrient solution will hold much more oxygen at 60°F (15°C) than it will at 75°F (24°C). Never let the nutrient solution temperature climb above 85°F (29°C). Above 85°F (29°C), the solution holds little oxygen. Roots are easily damaged by temperatures 85°F (29°C) and above. Heat-damaged roots are very susceptible to rot, wilts, and fungus gnat attacks.
     
----
    Soluble Salts Range Chart
    Electrical conductivity (EC) as milliSiemen (mS) and total
    dissolved solids (TDS) as parts per million (ppm)

    For nutrient solution determinations, one (1) mS (milliSiemen) or one mMho/cm 2 is equivalent to approximately 650 ppm total dissolved solids.
----
     

This