February 2022 - 43

PRODUCTION
MULTIPLE SYSTEMS
Multiple types of plants, or
multiple stages of the same plant
growing in the same climate
area also may require multiple
irrigation delivery systems in the
same area. Using the example
of propagation in the spring and
poinsettias in the fall, this may
be a drip or flood floor system
combined with an overhead
watering boom and would
provide efficient irrigation for
both types of crops in a single
climate zone. That 30 x 96 foot
area may benefit by three or four drip irrigation
zones and a single boom irrigator zone, or a
single flood floor and single boom zone.
CONSIDER THE SOURCE
Use the highest quality water to avoid using
RO to remove excessive salts - and dumping
25-40% of the water right off the bat or having
to implement a high leaching fraction to keep
salt buildup in check. If your well water is not
great, consider mixing it with or sole source
rainwater (unless you are in Colorado, then don't
consider rainwater, please; surface water or RO
if necessary but blended back with raw water to
minimize waste).
PULSE IRRIGATION
This requires a good irrigation controller or
computer system to execute but can reduce
overall water delivery and unnecessary leachate
by as much as 25%. A 2 liter per hour drip
emitter requires a single 15-minute irrigation
cycle to deliver an irrigation contribution of
0.5 liters. However, depending on the plant,
pot size and growing media, running that for
15 minutes straight may result in channeling of
the media and excessive leachate, or flooding
the pot. Dividing that 15-minute cycle into two or
three shorter cycles, dividing the irrigation cycle
into the stages of soil wetting, absorption and
saturation. This will often result in more uniform
distribution in the pot and reduce undesired
leaching. In some situations, it may also allow a
slight reduction in the total irrigation time and
water use.
RIGHT-SIZED IRRIGATION DELIVERY
Using two 4 liter per hour drip emitters or a
1 gpm overhead nozzle to water a crop of plants
that require the application of a 0.5 liter per day
will result in excessive leaching and water waste,
in addition to waste of expensive nutrients. In
flood irrigation systems, for example, most pot
sizes and growing media combinations will
take up 100% of the moisture they need and
70-80% of the moisture capacity of the pot
Shown here is a constant pressure variable speed
pump system. Professionally engineered and sized,
along with piping system, helps to supply consistent
specified flow and pressure to drip irrigation zones.
and allows an additional pump to be slid into place
when needed.
within a few minutes of being flooded. Yet I
continue to see flood cycles of 20 to 60 minutes
in many flood systems resulting in wasted water,
wasted nutrients and increased the plants
susceptibility to root and foliar diseases.
Selecting the right sized delivery devices and
systems also allows for a more efficient and
often smaller and more flexible irrigation water
management system (tanks, pumps, injectors,
pipes, valves, etc.). It may also reduce the
cost of treatment and filtration systems due to
reduced volumes and flow rates.
ADEQUATE PRESSURE AND FLOW
Oversizing of the delivery devices and systems
is a problem. However, undersized systems are
far more common, with an inadequate flow rate,
pressure, or both. This is quite common simply
due to the expanding nature of our industry. The
pumps and piping that once were adequate for
an acre are now being asked to service three
acres or more. Inadequate flow and/or pressure
result in poor and inefficient performance of
downstream irrigation delivery systems. Fog
and spray nozzles, drip emitters, and sprinklers
do not deliver their specified flow rates or cover
the same area they were designed to cover; the
nozzle or sprinkler may emit large drips, causing
damage to plants below; and irrigation cycle
times may no longer be adequate or may require
excessive time and resulting poor uniformity.
Irrigation distribution systems (pumps,
pipes) should be sized to provide higher flow
rates and higher pressures than the totals of
the downstream demand. I like to size pumps
and pipes for 25-30% over the calculated
demand. This will compensate for clogged and
sagging aging pipes, expected and unseen
leaks, reduced capacity resulting from the weardown
of pump impellers, and, of course, those
three or four extra bays or ground to grounds
just added. It is also a good idea to allow
installation space for the addition of another
pump in the future to accommodate that
expansion or additional demand in the future.
A larger and longer pump manifold is cheap
CLOSED LOOP IRRIGATION
There has been a continual rise in the use of
closed loop irrigation systems as the industry
expands and pressures increase to reduce runoff
and be more efficient with water use. Closed loop
irrigation systems can be a great way to address
this. Flood irrigation systems, deep water culture
(DWC) and nutrient film technique (NFT) systems
all come in several flavors now. Traditional flood
benches/tables, concrete flood floors, cascading
concrete floors, gravel flood floors, cascade/flow
troughs and unique hybrid combinations of two or
more of these are readily available and allow the
retention and reuse of up to 100% of irrigation
water not taken up by the plants.
These systems are safe and proven. All drain water
is captured, filtered, disinfected, reinjected with
fertilizer to replace nutrients that have been taken up
by the plants, and then pumped back out for the next
irrigation cycle. Adequate attention to this requires
an entire article ... or book ... of its own. Closed
loop irrigation works great, but not for all crops or
growing styles. Ask an irrigation professional for
direction on suitability.
IRRIGATION CONTROLS
Still one of my favorite subjects and, by my
observation, still one of the least understood by
many growers. Automate your irrigation. Go ahead
- just do it and you will see the results.
Automation involves more than just opening and
closing solenoid valves. Many growers find it easy
to turn over the opening and closing of valves to a
control system. That control is great
because Leroy the irrigator sometimes can't run
fast enough to turn on the next valve or waits too
long to close the valve because he's on
his cell phone. Automation of irrigation also should
include automating the decision of
when to irrigate each zone, and the automation
of pumping. Again, this deserves an article of
its own, or a book, several of which have already
been written so please Google those to learn more.
It will suffice to say that the major industry
computer control manufacturers have perfected,
or nearly perfected, this task and the choices in
programs, control methods, sensors and usability
have improved enormously over the past 30 years
and will pay for themselves in nearly every size and
type of growing operation.
Al Zylstra is manager of DRAMMwater, a segment of the
Dramm Corp. He can be reached at azylstra@dramm.com.
GREENHOUSE PRODUCT NEWS 43
February 2022

Table of Contents for the Digital Edition of February 2022
