SLOW WATER
The Best Ways to Water Your Plants
"Nothing in the world is more flexible and yielding than water. But against the hard and the strong, nothing outdoes it." - Lao Tzu, Tao Te Ching
Slow, fast, or just right?
Almost everyone knows that if plants don't get enough water they die. Most people also know that too much water can also kill plants. Most people don't know though that how fast plants get water is also an important factor.
The slower you water, the deeper it goes. The deeper the water goes, the deeper the roots go. The deeper the roots go, the more access plants have to moisture and nutrients, the stronger and more healthy they are, and the more resistant to high winds, drought, and pests. Flood irrigation is probably the worst way to water, then would come sprinkler systems, then drip irrigation, then auto-sensing drip methods like Blumat watering systems, then expensive and complicated computer controlled programs.
In Some Ways, Taking Care of Plants is Like Tuning a Guitar.
Like finding the harmony between too sharp and too flat, watering is finding the harmony between too wet and too dry. Everyone has had that moment of doubt, "did I water too much?" or "Is there enough water?" Most can recall a time or two when they damaged the health of one of their plants through an overzealous watering schedule or simply forgetfulness. Few however, recognize the current epidemic of ongoing, low-level overwatering. Mild over-watering is hard to detect. It doesn’t necessarily cause leaf droop and often presents no outward signs but dramatically decreases plant health and yields.
Over Watering
In the quest to increase quality and maximize yield, greenhouse conditions now approach environmental perfection. Yet in terms of watering with these ideal growing conditions, it can create some ironic liabilities. For example, greenhouses maintain high humidity levels to ensure the stomata of the plants stay open to maximize CO2 intake. Cool, humid mornings are the ideal opportunity for photosynthesis and greenhouse grows strive to replicate this time of day. This practice speeds growth, but plants are locked into this metabolic moment – that originally would only occur in nature for a relatively brief period during the earlier hours of the daylight.
Throughout the rest of the day, the plant's stomata will either open or close either to allow evapotranspiration to cool the plant in the hot sun or to conserve moisture if it’s in short supply. The afternoon is a critical time for moisture regulation, typically in the form of moisture conservation. This period also presents an opportunity to eliminate extra water in the soil. Transpiration through the leaves releases water, but a humid greenhouse may interfere with the process and growers must carefully regulate relative humidity and temperature - in addition to their watering schedule.
Ideal Irrigation
Hygrometers, thermometers and soil moisture meters help manage VPD, but the time-intensive process is best handled by an integrated automation system. One such system, Tropf Blumats, uses the principle of hydrostatic pressure to deliver water slowly and at the plant’s preferred rate, allowing each plant to determine its own irrigation schedule according to changes in VPD, which minimizes wasted water and the need for dehumidification. The ongoing assessment of VPD in relation to soil moisture can be a time-intensive effort. But when a plant-responsive irrigation system is in the equation, plants have a variable they can control to regulate their own health, so they can adapt better to changes in grow room conditions that may be mildly unfavorable. In fact, the plant’s response to irrigation might be the only way they can provide growers with definitive feedback. Cannabis ultimately communicate by asking for more water, when the language is dry soil, or refuses the water with a soggy signal that it’s had too much. When VPD is taken into consideration, irrigation can be planned from a better vantage point. Letting the plants manage their own water intake is a solution for this irrigation/transpiration/dehumidification cycle.