Cultivation & Conservation: Easy Ways for Marijuana Grows to Cut Water Usage

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By Fred Dreier

Water usage has become a focal point in the cannabis industry this year, with cultivators across the country battling droughts and water restrictions.

Growers in California have been hit the hardest, with a historic drought sending reservoir levels to record lows. Water rights activists in Northern California have asked marijuana cultivators specifically to cut back on their overall usage, which some believe has contributed to the drying of steams and creeks in several counties.

In Colorado and Washington, licensed growers are preparing to lose access to federal water after the Bureau of Reclamation announced it was cutting off water rights to the industry.

So how can cultivators cut back on their water usage – and lower their bills in the process? Marijuana Business Daily spoke with cultivation expert Ed Rosenthal, Ellis Smith of American Cannabis Consulting and Zeta Ceti of Green Rush Consulting for some advice. They said many marijuana cultivators use more water than they need and should look for ways to cut back regardless of whether they’re facing restrictions or in a drought. Here are some of their top tips for conserving water:

Shift Watering Strategy & Get Stingy

Growers who water by hand as well as those using automated systems commonly prefer to cut their workload by watering only a few times a week, using high volumes each time.

This method creates lots of waste, however, since the cannabis plant can only absorb so much water each time. Instead of dumping several gallons on each plant every three days, cultivators who grow in soil should microdose the plants, Ceti said. The idea is to water each plant more frequently, but in greatly reduced amounts.

Ceti said he commonly waters plants that are in a coco-based medium up to four times a day.

“The plant will eat what the plant will eat, but this way you’re reducing runoff,” he said. “You’re reducing your overall usage.”

Ceti said the best way to ensure water loss is kept to a minimum with this method is by using an automated system. Hand watering is effective, he said, but it is difficult to know exactly how much water is being poured.

Rosenthal said many cultivators actually over-water their plants because they assume that water must reach the base of each plant’s roots. This is not the case – water absorption happens high up in the root systems. So growers can afford to be somewhat stingy with their watering techniques when water supplies run low.

Rosenthal said every grower should purchase a moisture meter and measure how much water is in the soil at depths of 6, 12 and 18 inches.

“Once [water] goes below root level it is lost,” Rosenthal said. “Then you’re wasting water.”

Rosenthal cautioned growers to adjust their fertilizer usage accordingly when they switch to a new watering method. Taking water out of the system without also decreasing fertilizer can damage crops.

Catch and Store H2O

Farmers in arid climates have perfected catch-and-store methods, and the most common is a system for trapping rainwater. Growers who are serious about using rainwater should use all available roof space to catch and collect, or use tarps on their beds to trap water.

The American Rainwater Catchment Systems Association has a bevvy of literature designed to perfect catch-and-save systems on its website.

Rosenthal said that cultivators who operate indoors should also employ a catch-and-store method that utilizes dehumidifiers. While expensive, dehumidifiers can create a zero-loss system for water, he added.

“There is no reason to lose water in a closed system, because any water that the plant perspires into the air, the dehumidifier will bring back down,” Rosenthal said. “There is a considerable amount of water in a closed system.”

Water collected from dehumidifiers can contain organic contaminants that could be harmful for plants. While neither Rosenthal nor Ceti said purifying this water is a requirement, other cultivators believe in treating this water before it is used on plants.

Keep an Eye on Evaporation 

, Cultivation & Conservation: Easy Ways for Marijuana Grows to Cut Water UsageEvaporation is a major enemy for water conservation and can impact crops that are watered frequently. Rosenthal said he sometimes lays strips of carpet face-down below crops to combat evaporation and keep the ground insulated.

Smith, who came from a greenhouse background, said growers can also lower their light temperatures and increase the distance from lights to the plants to slow evaporation.

Many cultivators swear by the water-saving abilities of hydroponics farming, which recirculates water to crops. Some claim that these systems can use 10 times less water than traditional field crop cultivation.

Not all of the irrigated water is used the plants, and the excess can be captured and filtered in a fine-sand tank and then recycled into the system.

Smith said he believes most hydroponics setups actually lose more water due to runoff and water loss in the re-filtering process. Much of the water ended up going down the drain, he said.

“The drip watering mindset is still the best,” he said.

Photo credit: Copyright maxborovkov / 123RF Stock Photo