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Where drip irrigation fits in

By Chester Peterson Jr.

There are three main types
of irrigation in the country: gravity, center pivot, and subsurface drip
irrigation (SDI). Roger Brining has experience with all three on his Great
Bend, Kansas, and Alamosa, Colorado, farms.

His remarks about gravity
irrigation are unkind at best. “I hated it,” Brining says. “In fact, we rented
out all the flood-irrigated land because it wasn’t cost effective for us. As for
center pivots, I put one on any field where I have the opportunity to run a
full circle and can water all of its permitted acres.”


Mixed Results With SDI

“So far, on smaller fields,
I’m not seeing dramatically different yields for my SDI that’s 16 inches deep
on 40-inch centers than I’m seeing for my pivots,” he notes. “The SDI uses 25%
less water, though.”

Brining points out that,
depending on field size, SDI installation costs can range from $850 an acre
(when the pipelines are installed at 60-inch centers) to $1,500 an acre (on
40-inch centers) with automatic controls. Although there has been government
cost-share available of late to lessen that pain.

“With SDI, I have more
precise watering micromanaging it. For instance,” he says, “I can set the programs
early and late in the season to run a minimal .18 inch to .20 inch every two or
three days. Then in peak season, when usage picks up, I’ll run every single day
with the amount the crop requires, plus fertilizer as needed.”


Brining’s experience indicates
that SDI requires half the water of gravity irrigation, which represents a
dramatic savings. The only loss with SDI is the water used to flush filters.

Another advantage to SDI is
its ability to capture a heavy rain without runoff, since the top 8 to 12
inches of the field remain dry and sop up rainfall.

SDI has its shortcomings, he
points out. For example, a center pivot can be utilized to water up a newly
planted crop, which SDI is incapable of doing.

Brining double-crops 40% of
his cropland. Excellent germination is possible when seeding wheat into corn
residue only when moisture is applied by his pivots. But double-cropping beans
or milo into wheat stubble is where a center pivot can help the most with
germination, he believes.

The Challenge Of Rodents

Then there’s the rodent
problem. In his first year with SDI, Brining had to make a dozen gopher-caused
repairs to the buried dripline. And in order to prevent clogging of the
dripline pores, Brining uses filters that he periodically cleans. At the end of
the season he flushes with sulfuric acid to dissolve calcium deposits.

“I think that if you have
the water, it’s a good combination to pick up the corners of a center
pivot-irrigated field with SDI,” he advises.

Gravity Has Huge Drawbacks

Like Brining, Duane Ochsner
has been working with SDI to irrigate some odd-shape fields. As for gravity,
the Hastings, Nebraska, farmer says, “They’ve messed up more ground with land
levelers than they’ve helped around here. That’s because a lot of good soil got
buried. And there’s the lack of uniform application over a field, labor
intensiveness, and the inefficiency of gravity.”

Ochsner installed SDI in
60-inch centers 16 inches deep on two odd-shape fields five years ago. Those
fields couldn’t be irrigated via a center pivot. His cost for SDI was $1,100 an
acre, and that was with Ochsner and his family doing some of the installation


The main strong point of
SDI, he feels, is that with no evaporation, it’s almost completely efficient.

He thinks SDI is probably
best adapted for areas that have special needs, such as small or irregular
fields. That situation makes it easier to balance the higher initial cost for
installing SDI.

On the other hand, a center
pivot must be maintained and insured, and it’s subject to flat tires and strong
wind damage.

“Now compare center pivot to
gravity irrigation, say on the same size field (like a 160-acre field),”
Ochsner says. “With gravity, a 1,500- to 2,000-gallon-per-minute well and a
week or more of watering time are required. A center pivot will go around twice
in that same time and do it with an 850-to 900-gallon-per-minute well.”

He also says a center pivot
is unbeatable in getting a newly planted crop germinating and seeing daylight.

And, Ochsner adds, with a
pivot there’s less worry about proper filtering of sediment and sand plus zero
worries about unseen, chomping rodents as compared to SDI .


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