Irrigated, dryland grasses examined for profitability
Brent Bean, Texas AgriLife Extension Service agronomist, Amarillo, is trying to answer a question about the profitability of warm-season grass production for hay, or grazing, under dryland production and irrigation on the High Plains.
He says producers in cattle country are looking for an option to complement their row-crop program. But not enough is known about the production of some of the improved native and introduced warm-season grass species.
In a project funded in part by the Ogallala Aquifer federal initiative and a state cropping systems initiative, he began the study in 2007 by establishing six warm-season grasses at the North Plains Research Field south of Etter, Texas.
The grasses are Hatchita blue grama, Texoka buffalograss, WW Spar Old World bluestem, Haskell side-oats grama, Wrangler bermudagrass and Blackwell switchgrass. Each was planted under dryland, and limited and full irrigation.
• Warm-season grass in dryland and irrigated conditions studied.
• Some Old World bluestem had high yields for cattle production.
• Interest grows in some areas to return to native prairies.
Daily water use
Irrigation applications are based on data from a weather station that is part of the North Plains Potential Evapo-transpiration Network, which allows Bean and crew to determine daily water use.
“The fully irrigated plots are irrigated weekly with the amount of water needed to replace the water used from the previous week,” he points out, adding that the limited-irrigation lots receive half the amount of water and the dryland receives no supplemental irrigation.
In addition, both nitrogen and phosphorus have been applied each year based on soil tests to ensure nutrients did not limit yield potential, Bean says.
“Since 2008, we have been collecting yield and nutrient data,” he says.
Emalee Buttrey, AgriLife Extension assistant and a West Texas A&M graduate student, works on the project from a cattle-management standpoint, specifically cattle nutrition.
There was no extra water applied to dryland acres in 2008; the limited-irrigation plots received 7.33 inches; and the fully irrigated land received 14.7 inches from June through September. Rainfall in the growing season in 2008 was 5.84 inches, and for 2009 it was 6.13 inches up to September.
There was 0.72-inch irrigation applied to dryland plots after fertilizer in 2009 to help fertilizer incorporate, and 6.81 inches and nearly 14 inches applied in 2009 to limited and irrigated plots, respectively.
Not surprisingly, in 2008 with four harvests, yield increased with irrigation. “Some grass species responded differently to different amounts of water,” Buttrey says.
The Spar Old World bluestem produced the most tonnage over a season. But in gathering nutritive data, the energy value was highest with switchgrass and full irrigation.
“The highest level of crude protein was on dryland,” she says. “With less yield, we can have higher protein, since more of the nitrogen is available for conversion to crude protein.”
For the June 1 harvest, there was a marked response to water, Buttrey says. Bermudagrass on dryland was low yielding with 0.15 ton per acre, compared to 0.73 ton per acre for switchgrass. Because precipitation was almost nil during May and June, little forage was present in the dryland plots during the July 1 harvest, Bean says.
Under irrigation, the Old World bluestem in midsummer was the highest yielder, but it was low in June, showing the grasses respond differently to water at different times.
On Aug. 3, the blue grama, bluestem and side-oats grasses in the dryland block yielded about 0.4 ton per acre.
Highest yielding under full and limited irrigation were Old World bluestem, Haskell side-oats grama and bermudagrass.
Ledbetter is with Texas A&M Communications, Amarillo.
This article published in the March, 2010 edition of THE FARMER-STOCKMAN.