Underlying 80 percent of the High Plains is the Ogallala Aquifer, which provides water to nearly one-fifth of the wheat, corn, cotton and cattle produced in the U.S. The Ogallala Aquifer also serves as the main water supply for people throughout the High Plains. Unfortunately, this million-year-old, 174,000-square-mile underground reservoir is being depleted at an unsustainable rate.
Nearly 200,000 wells are withdrawing water from the Ogallala Aquifer. Estimated withdrawal rates are 10 to 50 times greater than recharge. In certain areas, the water table has dropped 100 to 200 feet. Through monitoring studies, it is estimated the aquifer will run dry in 50 years unless water consumption is decreased.
The Ogallala Aquifer is a crucial, but finite resource in the Texas High Plains where average annual precipitation ranges from 15 to 20 inches.
The Texas High Plains provide grazing for stocker cattle with wheat, alfalfa, warm-season grasses and other forages. Research at Texas Tech University, Lubbock, Texas, involves integration of beef cattle grazing systems with annual crop farming.
These systems can reduce inputs of limited irrigation water, as well as fertilizer and pesticides, while building soil organic matter and microbial diversity.
Crop choices by producers normally follow crop prices and input costs, which can lead to excessive water use. Limited planting of strategically irrigated crops and a perennial grass grazing-based beef industry extends water supply.
Research at Texas Tech University
Texas Tech University graduate studies play an integral role in the research of forage-based crop and livestock systems to better manage water, improve production efficiency and maximize profitability across the Texas High Plains.
Southern Sustainable Agriculture Research & Education (SSARE) has funded several graduate student grants at Texas Tech in addition to other funding to the university.
Lisa Baxter, a Ph.D. student in forage systems, explored regional novel forage species and grazing techniques to construct grazing systems that limit costly inputs and maximize productivity without jeopardizing environmental resources. The objective was to compare animal performance in an improved grass-legume pasture to a grass-only grazing system.
“Both systems contained native grass pastures of WW-B.Dahl Old World bluestem (OWB) and annual teff grass,” Baxter says. “In the grass-legume system, we interseeded alfalfa and yellow sweetclover into OWB at 15 percent of the forage composition. A small area of alfalfa and tall wheatgrass was managed as a protein bank. This smaller area contained 70 percent alfalfa and 30 percent tall wheatgrass.
“A protein bank allowed us to allocate our limited water resources onto a small land area which generates a high-quality supplement to other, warm-season grass-dominant pastures. Including legumes into the diet of grazing steers increased crude protein and forage digestibility, which improved animal weight gains from 150 pounds per acre in the grass-only system to 168 pounds per acre in the grass-legume system."
"Overall, these novel grazing management strategies offer promising methods for providing less water-demanding forage production on the Southern High Plains.”
Baxter also received a SSARE grant to test effects of winter irrigation and cover crop species on soil moisture depletion, cover crop yield and subsequent summer teff yield.
Water consumption by dryland and irrigated rye, wheat, burr medic, hairy vetch and rape-kale was compared to winter fallow for their effects on teff grass. Irrigation was used to supplement rainfall at a maximum of 1 inch per month.
“Results obtained during the first year of study showed both irrigated and dryland rye was the best overall option for supplying winter forage,” Baxter says. “Rye did not reduce soil moisture reserves or the following crop yield."
"Another year of data collection is in progress to determine how tillage regimes impact previous-year results. The tillage regimes are no-till and lightly disking the top 3 inches of soil as done in the first year.”
Victoria Xiong, graduate student at Texas Tech, is adding the ability to calculate forage yield of OWB in response to water supply. Texas Alliance for Water Conservation (TAWC) has online tools for calculating irrigation needs for cotton, corn and grain sorghum, but not for OWB.
“I am correlating plant growth to soil water content so a forage producer can predict forage yield depending on amount of rain or irrigation,” Xiong says. “This will allow a producer to plan ahead for forage production and determine cattle stocking rates in response to available water supply."
"We are making frequent measurements of forage growth and soil water content to facilitate calibration of a model for the Southern High Plains. A comparison is also being made of grazed OWB to grass cut for hay so that we can extend capability of the TAWC model to simulate water usage for both pasture and hay management.”
“Through our research programs, we’ve learned to use water-frugal old world bluestem in our grazing systems rather than the more popular bermudagrass, which needs a larger amount of water for growth,” says Chuck West, director for the College of Agricultural Science and National Resources (CASNR) Water Center at Texas Tech University.
“To improve the fair forage quality of bluestem, we grow it in a mixture of alfalfa and sweetclover and apply no more than 9 inches of irrigation water per year. The alfalfa-tall wheatgrass protein bank receives no more than 12 inches of irrigation per year. Over the past three years, we’ve averaged about 7 inches of irrigation on the bluestem-alfalfa mixture and approximately 10 inches on the wheatgrass-legume mixture.”
“Why do we use alfalfa?” West asks. “Alfalfa has a deep root system which allows it to use soil moisture from a greater depth than many of the other forage species. The great pasture potential of alfalfa is unrealized because most people think it needs 36 inches or more of irrigation. It does for high-yielding hay crops, but not for stocker beef cattle grazing.
“Fifteen to 20 percent alfalfa content mixed with the small area of alfalfa managed as a protein bank can produce an average daily gain of 2.1 pounds. This gain is 0.33 pounds higher than gain produced by steers grazing grass alone. When good-quality, water-efficient forage crops are raised with low to medium water input, the efficiency of converting water to animal gain becomes very good,” West says.
“A midseason hay harvest captures unused forage for later feeding,” West explains. “Hay harvest causes plant transpiration to quickly diminish, which conserves soil water for crop regrowth. It also prevents plants from developing low-digestible stems and nutrient-deficient leaves as they mature. Two inches of irrigation initiates regrowth resulting in uniform plant canopy.”
SSARE reports that research at Texas Tech University has increased awareness of critical water conservation needs across the High Plains. Producers are using information generated by Tech to initiate water conservation by targeting realistic yield goals rather than maximum production.
Information generated by Texas Tech University researchers has implications beyond the Texas High Plains and will help to sustain agricultural productivity while minimizing negative impacts on natural resources. 
PHOTO: With diminishing water availability, research addresses grazing strategies, crop choice and tillage methods to maximize natural resources. Photo by Lisa Baxter, Ph.D. graduate student at Texas Tech University.
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Robert Fears
- Freelance Writer
- Based in Texas
