Irrigation

Marijuana Horticulture

by Jorge Cervantes

Irrigation is a science unto itself. Irrigation cycles depend on plant size, climate conditions, and the type of medium used. large, round, smooth particles of substrate drain rapidly and need to be irrigated more often – four to twelve times daily for five to thirty minute cycles. Fibrous mediums with irregular surfaces, such as vermiculite, drain slowly and require less frequent watering, often just once per day.

The water comes to within one half inch of the top of the gravel and should completely drain out of the medium after each watering. Top-feed systems cycle for about five minutes or longer and should be irrigated at least three times daily. Often growers cycle the nutrient solution 24 hours a day, especially when growing in fast-draining expanded clay or similar mediums.

In fast draining mediums, overhead irrigation is continual. Drip irrigation in coco coir is four to five times daily. Flood and drain irrigation cycles are five to ten times daily.

During and soon after irrigation, the nutrient content of the bed and the reservoir as the same concentration. As time passes between irrigations, the EC and the pH gradually change. If enough time passes between irrigations, the nutrient concentration might change so much that the plant is not able to draw it in.