YOU WANT WET PLANTS, NOT SOAKED PLANTS
accurate sensors available for soilless
substrates, including stonewool, coco
fiber and soilless container mixes. These
root zone sensors measure the substrate
moisture status and allow the irrigation program to replenish the water in
the growing medium to a preset level.
Some irrigation sensors not only control
the nutrient application program but
may also measure EC and pH in the root
zone as well as temperature. While most
substrate sensors operate by providing
data to a computer-controlled irrigation program, for smaller gardens there
are hand-held moisture sensors that
can be used to check root zones, which
are connected to timer-based irrigation
schedules, to see if they are providing
the correct level of nutrients.
As with most indoor gardens, the
general recommendations are that nutrient application only occurs during the
lights-on period when plants are transpiring through their open stomata. The
first nutrient application of the day is
scheduled within an hour of lights on
and is usually the largest irrigation of the
day, with the highest amount of drainage
percentage to restore root zone moisture
and nutrient levels after the overnight
dry down. Irrigations are then scheduled throughout the day—the frequency
and volume of each can be based on
either targeted leachate volume percentages, as well as plant appearance and
substrate visual clues, or based on using
substrate moisture sensors linked to an
irrigation controller. Avoiding irrigation
at night when moisture requirements
are lowest helps prevent root saturation,
increase aeration and lower the risk of
pythium infection.
“
The first nutrient
application of the day is
scheduled within an hour of
lights on and is usually the
largest irrigation of the day.”
Irrigation scheduling is a vital aspect of
maintaining a high-yielding substratebased hydroponic system, but it takes
some understanding of plant water
usage and requirements to get a handle
on this process and avoid oversaturating the root zone. The use of increasingly
sophisticated technology for plant and
substrate moisture status monitoring
will become increasingly important for
many indoor gardeners when it comes to
the process of irrigation programming.
60
Maximum Yield USA | October 2016
Plant size, maturity and leaf surface area are significant factors in determining the correct
irrigation schedule.