This is probably the most commonly-asked question from commercial gardeners, but is one of the most difficult to answer. While most irrigation systems use constant supplies of water (due to predictable timer/pump schedules), Blumat systems deliver water based on demand.
This is great for saving water and getting the highest output of biomass per unit time, but is less than ideal for calculating water use. This is because plant demand for water is changing literally every moment.
Factors Influencing Water-Demand
- Ambient Humidity
- Ambient Temperature
- Ambient Light
- Plant growth stage
These are just a few of the influential factors that determine how much water your system might be using. In the middle of the night of a light-dep greenhouse, the tarp has been closed for several hours. This pushes humidity up, while light and temperature are down. The plants are also “asleep,” dramatically slowing their metabolic rates. This means that at this time, the plants are likely metabolising very little, if any water. A Blumat system in such a garden will be emitting little, if any water to match plant demand.
A few hours later, when the tarp is lifted and light comes in, humidity drops, temperature increases, and the plant fires hormones that signal it is time to metabolize and grow. During this time, the plants will be consuming significantly more water/nutrients, and the water use of the system as well as your plants will dramatically increase.
It should be obvious then, that the flow rate of a Blumat system is fluctuating at every moment based on environmental factors and plant-demand. Given the immense number of variables when considering each garden, it is virtually impossible to predict how much water a system will use.
However, it is almost a guarantee that a Blumat system will use less water than whatever irrigation is currently being used. Because plants are only given water as they use/need it, Blumat systems deliver the minimum necessary water to achieve optimal growth levels. They are the epitome of the old adage, “less is more!”
Why Not Use a Flow Meter?
This seems like the obvious answer to a system with fluctuating and unpredictable levels of water usage–just put a flow meter in the system, and see how much water you’re using, right?
Unfortunately, this is another hurdle that we have yet to get over. Flow meters, or other instruments that measure flow rates, require minimum flow rates to function. Blumat watering systems deliver water so slowly and gradually, that they fail to meet the minimum flow rate required by these meters. Therefore, most systems (with the exception of extremely large commercial systems) will perpetually read 0 on a flow meter, as if no water or nutrients have been delivered at all.
This is quite the conundrum, and an opportunity for a flow rate manufacturer–if you can make a flow meter with no minimum flow requirement, we’d love to offer it.
- Water use of Blumat Systems is variable and changes moment-to-moment
- Blumat Systems are extremely likely to reduce current water use
- Flow Meters do not work with the vast majority of Blumat Systems
- The variables influencing water use are so myriad that there is really no way to predict use rates