"Plants are like little motors or, more accurately, energy pumps," says Hank Bonnah, Hydra Unlimited's Chief Scientist and Principal Engineer. "Plants take in energy from sunlight (or indoor luminaries) and, through the process of evapotranspiration, move water from the roots to the leaves. With this water travels nutrients found in the soil in a substrate grow or, as in the case of Recirculating Deep Water Culture (RDWC) directly from nutriated water, and this feeds photosynthesis processes."
Many factors can impact the plants' ability to evapotranspiration at their maximum capacity. Both low and high air humidity impacts the process. Often measured as Vapor Pressure Deficit, VPD is related to air humidity and room temperature. Poor control of grow room atmospherics, such as VPD, can inhibit a plant's consumption of nutrients. Day after day of poor room environmental control can add up.
Hydra Unlimited scientists and engineers use the concept of "Growth Index" – the calculation of total canopy volume in square meters to evaluate progress. The amount of water released by the plants depends upon the total surface area of the leaves for a given environment. Think of it as a "green volume" in the room. The growth index can be affected by pruning techniques during vegetation as well as defoliating techniques employed during transition and flowering (though to a lesser degree). Hydra Unlimited's RDWC system is a closed-loop system wherein 99% of the water consumed is consumed by the plants' "green volume." Coupled with Hydra Unlimited's unique Tetrabase grow media (a breathable shield in which only 1% of the system water consumed is lost to system evaporation), both lost water consumption and HVAC load are dramatically reduced. Further, there is neither a need for extra "water runoff" nor is there a risk of underwatering that is a part of any substrate farming practice. This is why Hydra Unlimited offers minimum water and nutrient use with the potential of maximum yields while fully supporting Conservation Agriculture in the indoor space.
"There are some very interesting results of having a closed loop, conservation agriculture system" says Hank. "Because the relationship between growth index and water consumption is now available using Hydra Unlimited's RDWC system, the cultivator can begin to understand plant vitality by solely tracking water consumption."
The graph relates plant canopy volume to water consumption over time. At week 7, the room is falling behind (Brown/Yellow Run) versus an expected grow result (Green/Blue Run – past successful grow). The "Brown Run" is 85 gallons of water behind where it should be for maximum vitality (~22.5% difference). There is no need to actually measure the plants, and there is no need to have a camera in the room. All that is necessary is to plot water consumption. Leaf canopy volume is directly, and physically linked to water consumption. "Tools like Hydra Unlimited's RDWC allow us to change the structure of our thinking." Hank goes on to say, "We can rediscover what we already know: of course, more leaf area means more water consumed. This is not new. What is very new and extraordinarily exciting is we can discover what we, as cultivators, are doing right and what needs correction based solely on water consumption. We now have the ability to objectively measure and help our plants become their best selves with a minimum of resources consumed."
Made in the USA, Hydra Unlimited's HydraMax is a complete commercial deep-water culture system. With best-in-class aeration, nutrients are quickly and evenly delivered to each bucket simultaneously. This results in consistently faster vegging, higher yields and greater profits.
For more information:
Hydra Unlimited 
www.hydraunlimited.com