Time is Money

Metering pumps in center-pivot irrigation systems allow growers to apply
fertilizers and chemicals in the most precise, timely and cost-effective manner

Over many hundreds of years of trial and error, growers
have learned that the viability and optimization of their
crops relies on a series of operations that require precise
timing. The timing process begins in the spring when
climatic conditions are observed and past weather patterns
are consulted to determine the best time to plant the crop,
with different conditions more favorable for different types
of crops. The timing cycle concludes in late summer or fall –
again depending on the climate, weather patterns and type
of crop – when the grower chooses the optimum time for
his harvest.
In between planting and harvesting, though, there are a
number of other timing decisions that need to be made,
such as identifying the best times to apply nitrogen
fertilizers and chemicals (insecticides, fungicides and
herbicides) to the crop. Hand in hand with that is knowing
the precise amount of those products that should be applied
at the precise time. With the prices of fertilizers and the
chemicals used to make insecticides, fungicides and
herbicides continuing to increase, choosing the perfect
times to apply them and the precise amounts that should be
applied can often be the difference between a bumper crop
and one that fails to meet expectations.
Then, of course, even the best-laid plans can be scuttled by
the most fickle of players in this yearly drama: Mother
Nature. Knowing the best time to plant and harvest, as well
as the right time to apply fertilizers and crop protectants, is
helpful. However, one ill-timed hailstorm, or an infestation
of grasshoppers, aphids, corn borers or other insects or a
fungus outbreak can quickly turn what should have been,
for all intents and purposes, a profitable crop into a
scramble for survival.
It is during these moments when the unknown occurs that
a grower’s precise optimization of time can be the
most crucial.

Finding The Right Choice
As mentioned, trying to predict what can never be known
– just because it was 82ºF without a cloud in the sky from
June 13-26 last year doesn’t mean it won’t be 59ºF with a
foot of rain over the same time period this year – is the
most daunting challenge the grower faces every season.
This has forced growers to find, usually by weighing past
success against past failures, the best ways possible to
optimize their crop production.
Over the years, some basic guidelines have emerged when
it comes to applying fertilizers and chemicals:
• Fertilizers are generally applied to the crop at the time
of planting and again at multiple intervals throughout
the growing season, in precise amounts and at
precise times
• Different chemicals are applied at different precise
points during the growing season:
– Herbicides are generally post-emergent and
applied after the crop has come up, though there
are some that contain weed killer and can be
applied to the ground prior to crop germination
– Fungicides have traditionally been post-emergent,
but some newer formulations allow them to be
applied in a pre-emergent fashion
– Insecticides are usually applied when signs of an
imminent insect infestation begin to appear
With all of these fertilizers and chemicals needed to
ensure a maximized crop yield, the ultimate challenge for
the grower comes down to applying them in precise
amounts and at precise times while doing so in the most
efficient, environmentally friendly and energyconscious
Over the years, a number of technologies have risen to the
forefront where fertilizer and chemical applications
are concerned:
• In the United States and North America, metering
pumps are the most common technology used for
both fertilizer and chemical applications through
irrigation systems
• In Latin America, Venturi tubes are used to suck
fertilizer into the irrigation water supply
• In the Middle East and North Africa, metering pumps
are used to inject fertilizer, but with cheap labor
available, oftentimes chemicals may be applied
through such relatively primitive means as a
hand sprayer
In terms of inefficiencies, using Venturis is less precise
than using metering pumps, which can harm the bottom
line if overfeeding (more product is used than needed) or
harm the crop if underfeeding (the crop does not meet its
full potential). Also, relying on untrained manual labor
can often result in a level of fertilizer and chemical
application that is not what the grower expects
or requires.
One other method of application that is used throughout
the world – though it is in decline in North America – is
an aerial application where the chemicals are sprayed on
the crop from above. This mode of application has a
number of inherent drawbacks: aerial applications can be
expensive ($5 to $9 per acre in the U.S., with the cost of
the chemical on top of that), and they are susceptible to
wind-caused drift, overspraying or unintended applications.
The Ultimate Solution
For the grower looking to optimize cost, efficiency, return
on investment and, most important, yield, the ultimate
solution is a chemigation or fertigation system (which
consist of some combination of hoses, injectors, mixers/
agitators and product-storage tanks) that utilizes metering
pumps to introduce the grower’s desired amount of
fertilizers and chemicals – no more and no less – into the
farm’s center-pivot water irrigation system at the
precise time.
Metering pumps are perfect for these operations because
they are reciprocating positive-displacement pumps that
deliver precise amounts of fertilizers and chemicals, which
enables the grower to control the amount and the timing
of the application. They are highly accurate, repeatable
and provide flow rates that are easily adjustable. They are
also able to meet the unique handling characteristics
required for fertilizers (which are usually solutions) and
chemicals (which are often suspensions of fine particles
in liquid).
A chemigation/fertigation system that features a metering
pump is perfect for use with a center-pivot watering
system because the pump’s operations overcomes the
challenges that most perplex the grower. Anybody that
can use a calculator can set the needed flow rate for a
metering pump. Once the flow rate is determined, that
precise amount of fertilizer or chemical will be applied
through the center-pivot irrigation system. Because of the
metering pump’s efficiency, a large crop-growing operation
can effectively and efficiently use one pump to service up
to three center-pivot systems. Additionally, applying
precise amounts of fertilizer via a metering pump through
a center-pivot system at precise times during the growing
season will boost yield while needing less fertilizer to
realize those higher yields.
The use of metering pumps in conjunction with a centerpivot
system also keeps the grower more nimble and able
to adjust to changing growing conditions. For example:
• If fertilizer is applied other than by a center pivot one
day and the next day a storm leaches it away not only
is that fertilizer lost, but the chances are likely that
the field will be too wet for a number of days,
hampering the opportunity to apply another dose of
fertilizer. Applying the fertilizer through the center
pivot means it can be reapplied the next day, or when
the grower feels it is most appropriate. The ability to
adjust the metering pump’s flow rate also means that
more fertilizer can be applied with less water required,
which the crop doesn’t need after a heavy rain anyway.
• Metering pumps also provide benefits when insect
infestations occur. Growers will often know a few days
in advance if a wave of insects is entering the area.
When this happens, a mad scramble usually ensues as
competing growers try to contract with aerial sprayers
that can apply insecticides to their crops. The grower
using a metering pump for chemical application can
apply a precise amount of insecticide immediately
when needed through his center-pivot system to
thwart what could be a disastrous situation.
When considering metering pumps, one company stands
out – Neptune™ Chemical Pump Co., North Wales, PA.
Neptune’s hydraulic and mechanical diaphragm metering
pumps have become the industry standard in a wide
variety of applications, including irrigation, whether for
acres of corn or acres of country-club fairways. Neptune
has developed several families of metering pumps for
precise application of a wide variety of fertilizer and
chemical products in agricultural applications, including:

Series 500 pumps are hydraulically actuated diaphragm metering pumps with a micrometer
stroke adjustment dial to allow capacity changes while the pump is running or stopped
(10:1 turndown). Hydraulically actuated diaphragms offer the greatest life. Maintenance
is simplified through the use of valve cartridges that can be removed for cleaning or
replaced without disturbing the piping. They are available with flow rates from 1 to 80
gallons per hour in stainless-steel, PVC, Alloy 20 and Kynar® construction, making
them compatible with corrosive liquids. Series 500VS models offer special liquid ends
to handle suspensions of wettable powders or moderate viscosities. All moving parts
run submerged in oil for extended service life.

Series 7000 are mechanically actuated diaphragm metering pumps that eliminate the use of
contour plates on the liquid side of the diaphragm which improves flow patterns and
allows injection of suspensions. They are self-priming and have the ability to handle
chemicals with viscosities to 5,000 cP or that produce off-gas. Pump capacity can be
adjusted by a micrometer dial while the pump is running (10:1 turndown). They are
available with flow rates from 15 to 300 gallons per hour at pressures to 150 psi. All
models are available in stainless steel, PVC and Kynar® construction and all moving
parts run submerged in oil for extended service life.

PZ Series are electronically actuated diaphragm metering pumps and offer the industry’s
leading “pulse” design as the pumps operate on any single-phase voltage from 94 VAC
to 264 VAC, making them immune to low-voltage or ”brownouts.” Manual speed
adjustment allows operation from 15 to 300 strokes per minute (20:1 turndown).
Optional features include flow pacing, cycle timer and counter functions. Models are
available from 0.5 to 20 gallons per hour in PVC, acrylic and Kynar® materials of
construction. Models are available with an automatic de-gassing valve for chemicals
and liquids that “off” gas, such as sodium hypochlorite.

The ultimate benefit of utilizing metering-pump technology
for the application of fertilizers and chemicals through the
center pivot is the positive return to the grower’s bottom
line. The rising prices of fertilizers and chemicals make it
necessary to inject the exact amount of each at precisely
the right time. Aerial application of insecticides, fungicides
and herbicides is expensive and the timing of the
applications is not completely under the grower’s control.
A center-pivot irrigation system can cost upwards of
$80,000. A chemigation system that utilizes metering
pumps will cost $3,500 to $4,000, while a fertigation
system (which doesn’t require a mixer/agitator to keep the
product in suspension) can run between $2,500 and $3,000.
Using the center pivot as a spray boom for chemicals and
fertilizers allows reduced input costs, precision timing and
increased yields, money that can accelerate the repayment
of the original investment in the center-pivot system.
While growers will never be able to precisely predict
weather patterns (with any measurable accuracy), they can
expand the window of crop viability by making the best use
of the best application technology that is available. In this
case, that is metering-pump technology, which can be a key
and cost-effective component in any center-pivot
irrigation system.

Robert Gates is an Irrigation Product Specialist for Neptune™
Chemical Pump Co., North Wales, PA. He can be reached at
(970) 301-6294 or neptunepump@plains.net. For more
information on Neptune’s full line of products, please go to
www.neptune1.com. Neptune is a member of the Dover
Corporation’s Pump Solutions Group (PSG™), which is comprised
of the following leading pump brands – Almatec®, Blackmer®,
EnviroGear®, Griswold™, Mouvex®, Neptune™ and Wilden®.
You can find more information on PSG at www.pumpsg.com.