Irrigation Face Off

Center pivot or subsurface drip?

Farmers are professional decision makers. In every aspect of their work they are faced with choices and options to consider, even when it comes to irrigation systems.

Subsurface drip irrigation or SDI, a low-pressure, high efficiency irrigation system that uses buried drip tubes or drip tape to meet crop water needs is one option. SDI technologies have been a part of irrigated agriculture since the 1960s; with the technology advancing rapidly in the last two decades.

But how does an SDI system stack up to the more popular center pivots that roll over many of the irrigated acres in the Midwest?

“SDI systems are generally thought to be at least as efficient in terms of irrigation water use as center pivot irrigation systems, primarily because they avoid the evaporative losses that occur from exposing irrigation water on the soil surface and in the open above ground environment,” said K-State Extension Specialist, Daniel O'Brien.  “At K-State we have used conservative estimates of 10-20% water savings efficiency with SDI compared to center pivot irrigation.  In field situations were irrigation water availability is not limited, these efficiency gains may not be that important.  But where irrigation water supplies are more limited, 10-20% efficiency gains in irrigation water use could be extremely important and beneficial to an agricultural producer.”

It’s the system’s efficiency that attracted producers Jim and Jeff Reinert, a father/son farming duo from Ensign, KS. Their farm includes two separate SDI systems both 60 acres each, one with 30 inch tape the other with 60 inch.

“The thing you ultimately look for is the value of water,” Jim said.  “As water becomes more and more important to us, it’s something we need to do a better job of conserving.  We also want to be more efficient with our water allocations in relation to our acres. If we can maximize the productivity with a drip tape system to better use our water—that adds a value that is extremely important. Everything we can do to conserve water can only work in our benefit. I’ve been irrigating for the better part of 50 years and I hope my son has that same capability.

Jeff agreed that it’s hard to determine the monetary value of increasing your longevity as an irrigator. “The drip system definitely has merit—I wish it was a little more monetarily friendly but we just have to make the best of it and think long-term.”

A subsurface drip system may require higher initial investment and cost will vary due to water source, quality, filtration need, choice of material, soil characteristics and degree of automation desired. System cost, including installation, may range from $1,000 to $2,000 per acre. “The cost is really the only downside to the system we’ve seen so far,” Jim said.

The Reinert’s are no strangers to irrigation technology. Jim’s father was an early adapter on the western Kansas plains, and throughout the years they have progressed from one system to the next. Always irrigating and always seeking to irrigate better. “Learning the intricacies of the system are probably the most difficult, Jeff said. “There are more management responsibilities to the drip tape than there is to the flood irrigation or center pivots.”

Jim said that there’s still a lot to learn about drip tape systems, which will come with time and experience. “You simply have to manage it differently and really look more at water quality and water quantity,” he said. “Longevity is really key—so taking proper care of the system is a high priority.”

Normal life expectancy of a system is considered to be 12-15 years. Some systems have been reported to last 20 years with good maintenance and could last longer provided good quality water is used. SDI system life must be at least 10-15 years to reasonably approach economic competitiveness with full sized center pivot sprinkler systems that typically last 20-25 years.

While curiosity and interest continues to buzz around SDI, it’s important to do your homework about the system to determine if it’s suitable for your farming operation. “Farmers need to consider whether particular factors such as small or irregularly shaped fields, declining irrigation water availability, proximity to towns or production of high value-labor intensive crops may favor subsurface drip irrigation as opposed to center pivot or surface furrow irrigation systems,” O'Brien said.

Typically, SDI has higher investment costs as compared to other irrigation systems such as center pivot sprinklers. However, there are realistic scenarios where SDI can directly compete with center pivot sprinklers for production in the Great Plains.

A free Microsoft Excel spreadsheet template was introduced by K-State Research and Extension for making economic comparisons of center pivots and SDI systems and is available at http://www.oznet.ksu.edu/sdi/.