Even More Ways To Decrease Pumping Costs
PORTAGEVILLE, MO.
As if the current energy
costs for irrigators in the
southeast Missouri
(SEMO) region aren’t bad
enough, the one positive note
– the low-cost electricity – may
now become a thing of the
past. A June article in the
Chicago Tribune stated that
the pending environmental regulations that will
start in 2014, will lead to a 40 to 60 percent increase
in what consumers will pay for electricity.
The rate jump comes both from the high
cost of energy companies that have to retrofit
scrubbers onto existing coal-fired generating
plants (used in half the country’s energy generation)
which will be passed directly on to customers
and, secondly, from the fact that energy
companies will close down many coal-fired generating
plants rather than invest in the expensive
equipment to make them compliant. With
less power generation capacity online, the rules
of supply-and-demand take over.
Since energy costs are becoming more critical,
several agencies
have organized
an Irrigation Energy
Field Day to
take place
Thursday, July
28th at the MU
Delta Center in
Portageville to
assist local irrigators
with ideas
on how to decrease
energy
costs. Information
on how to
register and get
more information
for this free
Field Day can be
found below.
In the last
issue it was discussed
that savings
in irrigation
energy costs can
come from a variety
of ways.
The first three of
the broad categories
for decreasing
out of
pocket expenses for irrigation
were previously discussed:
1. Reduce the cost you
pay for fuel/energy.
2. Decrease Pumping
Head.
3. Improve the efficiency
of the pumping plant.
The last three categories
will be discussed now:
4. Decrease losses in irrigation
systems so pumps
don’t run as long.
5. Agronomic ways to either
reduce crop water requirement
or decrease
water losses.
6. Miscellaneous methods.
Water Loss in Irrigation
Systems. Cutting down water loss to evaporation,
deep percolation, and run-off improves
an irrigation system’s application
efficiency (AE), resulting in pumps not having to
run as long. Methods to increase AE depend on
the irrigation method used.
Pivot Irrigation. Water loss to evaporation
and wind drift can be reduced by dropping nozzles
lower to the ground with pivot drops. Also,
serrated splash plates that break up a nozzle
stream into “spider legs” are more efficient than
flat-surface splash plates that splatter the nozzle
stream into tiny droplets. Nozzles that shoot
out rotor streams are even more efficient. The
smaller the droplet or rotor stream, the higher is
the loss. Retrofitting a pivot with a low pressure
nozzle package (an energy savings in and of itself
just from lower input pressures) has the
added energy benefit of increasing AE by creating
bigger droplet sizes and reducing pressure
which tends to atomizes droplets.
Furrow Irrigation. The biggest improvements
in AE for furrow systems come from items that
allow the furrows to get out faster to the end.
This increases AE and reduces energy as most
farmers key on turning off pumps based on the
majority of water furrows being “out” getting
them out faster, means turning off the pump
sooner. Surge flow, shorter runs, and “cut back
irrigation” (CBI) help. If you use a diesel or
propane engine, CBI is remarkably simple and
effective. One merely revs up high to start out
with, thus putting more water into every furrow
and thus making them advance faster. When
the water furrows are about 3/4ths the way out,
idle the engine back to avoid runoff. This operation
could easily be set up with a Murphy
switch to make it simpler yet. Because of the
high flow rates we have in the Delta, we are one
of the few places in the irrigation world that can
readily use CBI. We probably ought to be taking
more advantage of it.
As implied above, larger furrow streams lead
to faster advancement down the field. One can
double furrow stream size by cutting in half the
number of furrows watered in a set by using an
extra half roll of Polypipe plus a tee, Y, or surge
valve that lets the flow be moved back and forth.
The half-roll waters the furrows closest to the
tee, whereas, the full roll doesn’t have any orifices
punched in until half way. Most SEMO furrow
irrigators water every 2nd furrow; going to
every 3rd, every 4th, etc. will increase furrow
stream size. However, the jury is out on whether
yields are impacted.
Flood Irrigation. The use of multi-inlet Polypipe
is felt to reduce pumping costs by 15 to 20
percent. Also, if there are sandy portions in rice
fields, they should be bermed up and planted to
soybeans. These sandy spots act like a bathtub
drain. Running an EM machine over the field
will produce a map of soil textural differences
that can be used to identify areas that will seep.
Agronomic Methods. Irrigation pumping requirements
can be decreased by the choice of
plant/hybrid grown and when it is planted.
Early planting can decrease crop water needs
because the weather is milder and more rainfall
can be harvested. Minimum-till and narrow-row
planting will lead to some water savings. The
University of Nebraska has suggested that irrigators
apply 100 percent of the corn water
needs during tasselling and silking, and 75 percent
at all other times. This leads to an energy
saving with only a 3 percent drop in yield. Two
technologies can help decrease energy use. The
first is a wonderful method that keeps over-irrigating
from happening. Wireless moisture sensors
are being used by more and more people in
SEMO. Such a monitoring system using moisture
blocks and a canopy temperature sensor is
seen being installed (Figure 1). The very exciting
thing about this technology is that area
farmers and irrigation companies have become
local dealers. Formerly, the customers of these
wireless sensor manufacturers were PhD researchers
doing small-plot work, and these
companies didn’t quite understand the real
needs and requirements of the farmer. Now we
have farmer talking to farmer and dealers that
are well acquainted with the needs of their customer.
Another device that can save irrigation energy
costs is on the other spectrum of technology,
and was a tooled developed during the Dust
Bowl – furrow dikers. Furrow dikers are simple
paddle-wheel devices that are attached to a tool
bar. A paddle blade drags the soil between two
furrow beds and when the pile of pulled soil gets
heavy enough, it flips the paddle wheel making
a mini basin. Figure 2 shows furrow dike basins
catching water in a rain storm in Georgia. Russell
Nuti of the USDA/ARS National Peanut Research
Laboratory in Georgia has found energy
savings and yield increases for a number of
crops, including peanuts, cotton, and corn.
Fig. 2. Furrow dikes capturing water during a
rain event in Georgia.
Miscellaneous Methods. Well efficiency, the
amount of water produced per foot of drawn
down, effects irrigation pumping requirements.
Using the proper size of gravel pack and screen
size will mean that the well does not draw down
as deep as one that is incorrectly designed. In
some parts of the SEMO area ponds could be
used to capture to catch rainfall. Pulling water
from a pond requires less head than pulling it
from a well.
More information on energy savings for irrigated
agriculture will be found at the Irrigation
Energy Field Day to be held in Portageville, MO
on Thursday, August 28th. Δ
DR. JOE HENGGELER: Extension Agricultural
Engineer, University of Missouri