Water Quality

Marijuana Horticulture

by Jorge Cervantes

The concentration of calcium (Ca) and magnesium (Mg) indicate how “hard” the water is. Water containing 100 to 150 milligrams of calcium (CaCO3) per liter is acceptable to grow marijuana. “Soft” water contains less than 50 milligrams of calcium per liter and should be supplemented with calcium and magnesium.

Water with high levels of chloride frequently contains high levels of sodium, but the opposite is not true. Water with high levels of sodium does not necessarily contain excessive levels of chloride (chlorine).

At low levels sodium appears to bolster yields, possibly acting as a partial substitute to compensate for potassium deficiencies. But when excessive, sodium is toxic and induces deficiencies of other nutrients, primarily potassium, calcium, and magnesium.

Chloride (chlorine) is essential to the use of oxygen during photosynthesis, and it is necessary for root and leaf cell division. Chloride is vital to increase the cellular osmotic pressure, modify the stomata regulation, and augment the plant’s tissue and moisture content. A solution concentration if less than 140 parts per million (ppm) is usually safe for marijuana, but some varieties may show sensitivity when foliage turns pale green and wilts. Excessive chlorine causes the leaf tips and margins to burn and causes the leaves to turn a bronze color.

Simple water filters do not clean dissolved solids from the water. Such filters remove only debris emulsified 9suspended) in water; releasing dissolved solids from their chemical bond is more complex. A reverse osmosis machine uses small polymer, semipermeable membranes that allow pure water to pass through and filter out the dissolved solids from the water. Reverse osmosis machines are the easiest and most efficient means to clean raw water.