Is there a better way to grow alfalfa? Which cultivars are suited to the semi-arid Texas environment, where precipitation often limit yields and productivity?

Researchers at the Texas A&M University System's Agricultural Research and Extension Center here are looking for answers to those questions.

"Alfalfa is a very important hay and grazing crop on the Texas Rolling Plains," said Dr. Dariuz Malinowski, Texas Agricultural Experiment Station assistant professor-forages. "Wilbarger County, where our center is located, is a top producer of alfalfa statewide."

Higher energy prices, inadequate supplies of surface water and declining water tables due to repeated drought are affecting producers' profitability and productivity, Malinowski said.

"We started our alfalfa research in 2002 to evaluate productivity, drought tolerance and persistence of alfalfa cultivars under irrigated and rain-fed (dryland) conditions," he said. "We are looking at how alfalfa responds to defoliation and water stress. Hopefully, our work will give producers a better understanding of available cultivars, help them make wise choices and lead to ways we can reduce water use and production costs while maximizing returns."

Malinowski conducted this research with Dr. William Pinchak, Experiment Station ruminant nutritionist based at Vernon; research associate Betty Kramp and technician Matt Angerer.

According to the Texas Agricultural Statistics Service, Texas producers harvested more than 855,000 tons of alfalfa from 150,000 acres in 2004, with an average yield of 5.7 tons per acre. These producers received an average price of $132 per ton and generated more than $112 million in farm-gate receipts statewide.

Water is the limiting factor in alfalfa production. The crop's water use requirements, or thirst, is directly related to the length of the growing season. At Vernon, the growing season is typically about 221 days.

"Previous research has shown that it takes about 23 inches of water for alfalfa to hit its maximum potential of forage yield production,"

Malinowski said. "In terms of yield, conventional wisdom holds that alfalfa can require between 4 and 10 inches of irrigation to produce a ton of yield. The crop's total water requirement in this area is met by a combination of available soil moisture, seasonal rainfall and supplemental irrigation."

Average annual precipitation on the Texas Rolling Plains varies from 19 inches in the west to about 25 inches in the east. Most of this rainfall occurs in spring and fall, but alfalfa's peak water demand typically occurs in July.
To compare performance, the researchers planted 16 different cultivars representing alfalfa fall dormancy ratings from 1 to 8, using seed provided by several seed companies. They used common cultural practices for seedbed preparation and planting. They also used herbicides to control winter annual weeds during crop establishment, and treated for insect pests as necessary.

"We are fortunate that alfalfa faces little or no insect or disease pressure here in Wilbarger County," Malinowski said. "Aphids and armyworm larvae can be a problem, but we do not have to deal with blister beetles at all."
All of the cultivars were grown dryland and under limited irrigation.

Irrigated plots were watered to simulate traditional flood irrigation and meet the difference between the actual precipitation and long-term monthly average precipitation for May through October.

In order to test their hypothesis that profitable yields could result from limited or reduced irrigation, the researchers chose varieties with a range of fall dormancy ratings.

"Fall dormancy is rated on a scale of 1 to 9. Varieties with a higher dormancy rating, say 7 or 8, are less dormant in fall and winter," Malinowski said. "In North Texas, varieties with fall dormancy ratings of nine or higher may be too susceptible to freezes. Varieties with a lower rating typically go dormant during this time because they are more adapted to areas with colder winters.

"We think varieties with a higher fall dormancy rating may be better suited to the Rolling Plains because they are more active in spring and fall when we get most of our rainfall."

The researchers harvested their plots when the plants exhibited 10 percent bloom. This is the accepted growth stage for harvest, when the plants are high in protein that makes good hay. Their irrigated plots made up to eight cuttings in the growing season, while their dryland plots only produced three to four cuttings.

Rainfall during the May through October growing season of the study varied widely, from a high of 28.1 inches in 2002 to 11.4 inches in 2003, 18.6 inches in 2004 and 19 inches in 2005. Supplemental irrigation also varied, from 7.2 inches in 2002 to 12.2 inches in 2003, 5.8 inches in 2004 and 6 inches in 2005.

After four years of comparing alfalfa cultivars, the researchers reached these conclusions:

• Under dryland conditions, all alfalfa cultivars produced about the same yield – roughly 2.5 tons of dry matter per acre.
• Under partial irrigation, cultivars that are less fall dormant – those with higher fall dormancy ratings – produced more total forage per acre. "Cultivars with a fall dormancy rating of 5 to 8 produced an average of 9 tons of dry matter per acre," Malinowski said. "Cultivars with fall dormancy ratings of 1 to 4 only produced an average of 7.5 tons per acre. "Cultivars that are less fall dormant produced more because they are active in spring and fall. They also seem to be more efficient in utilizing the available water."
• All cultivars grown under partial irrigation in 2003, 2004 and 2005 produced an average of 8.5 tons of dry matter per acre.
• "Texas Common," a popular cultivar of unknown parentage was a top performer in both dryland and limited irrigation trials. It produced 2.6 tons of forage per acre under dryland conditions, and 9.5 tons of forage per acre under limited irrigation.

"We thought improved cultivars would out-produce Texas Common, but this mainstay cultivar held its ground well," Malinowski said.

"The main take-home message is that we were able to produce a ton of yield from all cultivars under partial irrigation on less water," he added. "We averaged a ton of dry matter forage yield per 2.94 inches of supplemental irrigation. Conventional wisdom says you are going to apply at least 4 inches or more to get a ton of yield.

"The second take-home is to be sure the cultivar you choose is adapted to and tested in your area. We made very good yields with less fall dormancy, and we saw good recovery from hard freezes in this area. The third take-home is to water adequately during the time of intensive growth, when your alfalfa is regrowing after a cutting."
The researchers plan to continue their alfalfa studies. They want to compare forage quality among the cultivars grown, run an economic analysis on costs and returns, and include genetically modified cultivars in future trials.
"All of the cultivars we have studied so far are entirely natural, none are genetically modified," Malinowski said. "But we hope to expand the study to evaluate RoundupReady varieties in the future, with the help and cooperation of the Noble Foundation in Oklahoma."