Return on Investment
Apples and oranges may be the best way to describe Anthony’s ROI of drip vs. center pivot. But his improved irrigation efficiency strongly contributes to the economic competitiveness of SDI.
“We’re in an area where water regulations permanently remove any land not watered two out of the last 10 years from ‘irrigated’ status, so the tape is a defensive measure for our balance sheet,” Anthony says. “Comparison with our (center pivot) circles is not apples-to-apples.”
Pivots are more expensive to install on odd-shaped fields than large fields, he says.
“However, our irrigation efficiency is much better with drip. The drip system typically uses 65-75% of the water and energy needed to irrigate with a pivot. It often uses less than one-third of furrow watering.”
Lamm notes that on similar smaller fields, the cost of a center pivot per acre may be about the same cost of SDI. “In addition, SDI will likely be able to irrigate more of the land area in these odd shaped parcels,” he says.
Initial cost of Anthony’s drip system was about $1,400/acre. Common SDI systems cost from $1,200 to $1,400/acre, compared to about $800-1,000/acre for a typical 132-acre circular pivot,” says Inge Bisconer, technical marketing manager for Toro Micro Irrigation.
“Pivots can be even more if they’re fitted with swing arms to irrigate the corners. On the other hand, SDI systems can easily accommodate both square fields or odd shaped fields, irrigating over 155 acres of a typical quarter section.”
Lamm, who has led K-State SDI research more than 20 years, says yields from SDI can compete closely with pivot irrigation using much less water. “Careful management of SDI systems reduces net irrigation needs by nearly 25%, while still maintaining top yields of 200 bu./acres,” he says.
“The 25% reduction in irrigation needs potentially translates into 35-55% savings when compared to sprinkler and furrow irrigation systems which typically operate at 65%-85% application efficiency.”
A seven-year field study the past decade compared simulated low energy precision application (LEPA) sprinkler pivot irrigation to SDI for corn and soybean production on silt loam soils in northwest Kansas. LEPA corn averaged 235 bu./acre, while SDI averaged 233.
“There was little difference in average corn grain yields between system type across all comparable irrigation capacities,” Lamm says. “However, LEPA had higher grain yields for four extreme drought years (about 15 bu./acre more) and SDI had higher yields in three normal to wetter years (about 15 bu./acre more).”
Lamm says there were no significant differences in soybean yield (73 bu./acre for SDI compared to 70 bu./acre for LEPA). Lamm says there was a trend toward SDI having greater yield at deficit irrigation levels and LEPA having greater yield at the full irrigation level.