Water Quality

Hard Water

The concentration of calcium (Ca) and magnesium (Mg) indicate how "hard" the water is. Water containing 100 to 150 milligrams of calcium (CaCO,) 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.

Roots on this clone have reached the wall of the container.

Sodium Chloride and Water Quality

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 of 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 (suspended) in water; releasing dissolved solids from their chemical bond is more complex. A reverse-osmosis machine uses small polymer, semi-permeable 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.

Total Dissolved Solvent Machine Photo

Semi-Permeable Membrane and adjust when necessary.

/ ■ y

Pure Water

Solution /

/

Semi-Permeable Membrane

Check the pH of the irrigation water drawing shows that pare water with no salts or dissolved solids and adjust when necessary.

migrates to the solution with more dissolved solids.

Osmosis

The roots draw the nutrient solution up the plant by the process of osmosis. Osmosis is the tendency of the fluids to pass through a semipermeable membrane and mix with each other until the fluids are equally concentrated on both sides of the membrane. Semi-permeable membranes located in the root hairs allow specific

This reverse osmosis machine transforms water with a high ppm or EC into water with less than 10 ppm.

This reverse osmosis machine transforms water with a high ppm or EC into water with less than 10 ppm.

TYPICAL ANALYSIS

mg/1

mg/1

CALCIUM, 55 SULPHATE 13

MAGNESIUM 19 NITRATE <0.1

POTASSIUM.

SODIUM 24 ALUMINIUM 0

BICARBONATE 248 DRY RESIDUE

CHLORIDE 37 ATISO'C 280

pH AT SOURCE 7.4

The dissolved solids in this bottled water are measured in milligrams per liter (m/l).

nutrients that are dissolved in the water to enter the plant while the other nutrients and impurities are excluded. Since salts and sugars are concentrated in the roots, the electrical conductivity (EC) inside the roots is (almost) always higher than that outside the roots. Transporting the nutrients by osmosis works, because it depends on relative concentrations of each individual nutrient on each side of the membrane; it does not depend on the total dissolved solids (TDS) or EC of the solution. For nutrients to be drawn in by the roots via osmosis, the strength of the individual elements must be greater than that of the roots.

But, the transport of water (instead of nutrients) across the semi-permeable membrane depends on EC. For example, if the EC is greater outside the roots than inside, the plant dehydrates as the water is drawn out of the roots. In other words, salty water with a high EC can dehydrate the plants.

Reverse-osmosis machines are used to separate the dissolved solids from the water. These machines move the solvent (water) through the semi-permeable membrane, but the process is reversed. It moves from lower concentrations to higher. The process is accomplished by applying pressure to the "tainted" water to force only "pure" water through the membrane. The water is not totally "pure" with an EC of "0," but most of the dissolved solids are removed. The efficiency of reverse osmosis depends on the lype of membrane, the pressure differential on both sides of the membrane, and the chemical composition of the dissolved solids in the tainted water.

Unfortunately, common tap water often contains high levels of sodium (Na), calcium (Ca), alkaline salts, sulfur (S), and chlorine (CI). The pH could also be out of the acceptable 6.5 to 7 range. Water containing sulfur is easily smelled and tasted. Saline water is a little more difficult to detect. Water in coastal areas is generally full of salt thai washes inland from the ocean. Dry regions that have less than 20-inches-annual rainfall also suffer from alkaline soil and water that is often packed with alkaline salts.

Table salt, sodium chloride (NaCI), is added to many household water systems. A small amount of chlorine, below 140 ppm, does not affect marijuana growth, but higher levels cause foliage chlorosis and stunt growth. Do not use salt-soft-

ened water. Salty brackish, salt-softened water is detrimental to cannabis. Chlorine also tends to acidify soil after repeated applications. The best way to get chlorine out of the water is to let it sit one or two days in an open container. The chlorine will evaporate (volatilize) as a gas when it comes in contact with the air. If chlorine noticeably alters soil pH, adjust it with a commercial "pH UP" product or hydrated lime.

The metric system facilitates the measurement of "dry residue per liter." Measure the dry residue per liter by pouring a liter of water on a tray and allowing it to evaporate. The residue of dissolved solids that remains after all of the water evaporates is the "dry residue per liter." The residue is measured in grams, Try this at home to find out the extent of impurities. Fertilizers have a difficult time penetrating root tissue when they must compete with resident dissolved solids.

Water that is loaded with high levels of dissolved solids (salts in solution) is possible to manage but requires different tactics, Highly saline water that contains sodium will block the uptake of potassium, calcium, and magnesium. Salt-laden water will always cause problems. If water contains 300 ppm or less dissolved solids, allow at least 25 percent of the irrigation water to drain out of the bottom of containers with each watering. If raw water contains more than 300 ppm of dissolved solids, use a reverse-osmosis device to purify the water. Add nutrients to pure water as a way to avoid many nutrient problems.

Dissolved salts, caused by saline water and fertilizer, quickly build up to toxic levels in container gardens. Excessive salts inhibit seed germination, burn the root hairs and tips or edges of leaves, and stunt the plant. Flush excess salt buildup from growing mediums by applying two gallons of water per gallon of medium and repeat leaching using a mild pH-corrected fertilizer solution. Leach growing medium every two to four weeks, if using soft water or saline water. Hard water and well water in dry climates are often alkaline, and usually contain notable amounts of calcium and magnesium. Cannabis uses large quantities of both nutrients, but too much calcium and magnesium can build up in soil. In general, water that tastes good to people also tastes good to cannabis.

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