Irrigated, dryland grasses studied for profitability
Dr. Brent Bean, Texas AgriLife Extension Service agronomist in Amarillo, is trying to help answer a question about the profitability of warm-season grass production for hay or grazing under dryland and irrigation in the High Plains.
In a region known as cattle country, Bean said producers are looking for an alternative that would 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 and varieties.
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.
The six grasses were: Hatchita blue grama, Texoka buffalograss, WW Spar Old World bluestem, Haskell sideoats grama, Wrangler Bermuda grass and Blackwell switchgrass. Each grass was planted in blocks under dryland, limited and full irrigation conditions.
The irrigation applications are based on data gathered from a weather station that is part of the North Plains Potential Evapotranspiration Network, which allows Bean and his crew to determine water use on a daily basis.
"The fully irrigated plots are irrigated weekly with the amount of water needed to replace the water used from the previous week," he said, adding the limited-irrigation plots 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 test analyses to ensure that nutrients did not limit yield potential, Bean said.
"Since 2008 we have been collecting yield and nutrient data," he said.
Two papers on the results can be found at http://amarillo.tamu.edu/programs/agronomy/publications/Other.
Emalee Buttrey, AgriLife Extension assistant and West Texas A&M University graduate student, is working on the project from a cattle-management standpoint, particularly cattle nutrition.
There was no additional water applied to the dryland in 2008, the limited-irrigation plots received 7.33 inches and the fully irrigated received 14.7 inches from June through September, Buttrey said.
Growing season rainfall in 2008 was 5.84 inches and so far in 2009 there's been 6.13 inches, she said. There was 0.72 inch of irrigation applied to the dryland plots after fertilizer this year to help get the fertilizer incorporated; and 6.81 inches and almost 14 inches were applied this year to the limited and irrigated plots, respectively.
"We made four harvests last year and, as we would expect, as irrigation levels increased, the yield increased," Buttrey said. "Some grass species responded differently to different amounts of water."
The Spar Old World bluestem has produced the most tonnage over the entire season, she said. When gathering nutritive value data, the energy value was highest with switchgrass under full irrigation.
"The highest level of crude protein was on dryland," Buttrey said. "With less yield, we can have higher protein since more of the nitrogen is available for conversion to crude protein."
During the June 1 harvest this year, there was a marked response to water, Buttrey said. Bermuda grass on dryland was pretty low yielding with 0.15 tons per acre compared to 0.73 tons per acre for switchgrass.
"As we increase water, we increase yield in all of the grasses," she said.
Because precipitation was almost nonexistent during May and June, very little forage was present in the dryland plots during the July 1 harvest, Bean said.
Under irrigation, the Old World bluestem in July was the highest yielder, but it was low in June, Buttrey said, showing the grasses respond differently to water at different times. On Aug. 3, the blue grama, bluestem and sideoats grasses in the dryland block yielded about 0.4 tons per acre.
"So far this year, the highest yield under full and limited irrigation has been with the Old World bluestem, (Haskell) sideoats grama and Bermuda grass," Bean said.
The grass plots will receive one more cutting in September, and a final nutritive value analyses for each harvest will be completed, Buttrey said.
Dr. Larry Redmon, AgriLife Extension forage specialist from College Station, said his primary interest is in the dryland grasses to absolutely reduce the amount of water used in the production system.
"Getting some warm-season perennial grasses established was the goal," Redmon said. "I think there will be a lot of interest eventually in people going back to grass. One question we had was: How do introduced warm-season perennial grasses compare with the native species?"
He said while there are several native grass species found in the High Plains, three species -- buffalo grass, blue grama and side oats grama -- are the most dominant.
"But there's been interest in the past in putting Bermuda grass under a circle (of irrigation). Due to the demand for water and fertilizer and coupled with a short growing season in the High Plains, Bermuda grass has not proved economically viable for most producers," Redmon said.
He said some Conservation Reserve Program fields have Old World bluestems that haven't had a bit of care but have persisted for many years, and that a small amount of nitrogen fertilizer can go a long way with them.
Spar is a variety that has a reputation of having the highest level of drought tolerance among the Old World bluestems, Redmon said. In the Plains mixture of 30 different grass lines, Spar rose to the top for drought tolerance.
"There's others that probably have a higher nutritive value, but might not have the cold or drought tolerance of Spar," he said.
WW B Dahl is another Old World bluestem with promise, Redmon said, although its lack of cold tolerance is still up for discussion. It is late-maturing, produces more nutritive value, but it doesn't have quite the level of drought tolerance as does Spar.
"I'm a little concerned about Bermuda grass up in this country," he said. "It's probably not the best idea. Likely we'll have $1,200-a-ton phosphorus again and $700-a-ton urea again. As we look down the road at declining water resources for irrigated agriculture and the projected increases in fertilizer costs, my attention is drawn to these natives."
Even in the Brazos Valley and the Trinity River Basin, there's a tremendous interest in restoring these Bermuda grass fields to native prairie vegetation, Redmon said.