Alfalfa is native to semi-arid southwest Asia, and countries such as Iran, Georgia and Afghanistan, where it has developed under very hot, dry conditions. Although much of it is irrigated, it also grows on rangeland as well, and it can be successful in the dry areas of the United States with help from grass varieties.
“Our overall aim is to help producers in the Texas High Plains and elsewhere, transition toward lower water use by integrating grazing into cropping systems so it’s not just all cotton or all corn,” said Chuck West, plant and soil science professor at Texas Tech University. “We’re all aware of the water supply declining in the Ogallala Aquifer. My work is in low-cost pasture production, improving the quality of pastures and a particular interest in tracking the amount of water it takes to grow the forage. Alfalfa is famous for being a high-water using crop, but my emphasis is on grazing alfalfa in mixture with grasses. We want to take advantage of two fantastic traits alfalfa has, one is that it fixes its own nitrogen due to its deep roots and the other is that it has a high nutritive value.”
The conventional use of alfalfa is as a highly irrigated, high water use, multiple cuttings crop for dairy farms and to sell as a commodity. However, West sees alfalfa’s potential as a low-water input crop, used as a protein bank for grazing and mixed with perennial grasses. A protein bank is a small acreage of high-protein forage for limit grazing in rotation with a large acreage of low-protein forage. Rye and wheat are widely grown across the southern Plains with winter-dormant, warm-season grass with limit grasses. They work well while the cattle also have a stockpile of bermudagrass or Old World bluestem.
West said the main warm-season perennial grass that he uses with alfalfa is a type of Old World bluestem grass called WW-B. Dahl. It is a low-water use grass that is late flowering in July or early August, which is a big advantage over the native warm season grasses that flower and become stemmy.
“This means it stays leafy during June and July and we can get some very good grazing out of it,” West said. “It support average daily gains of anywhere from 1 to 2.5 pounds per day. Typically it’s more like 2.5 in the May, June and early July months, then it drops down to about a pound to a pound and a half later in the season.”
West said in an alfalfa and grass pasture mixture with no nitrogen applied, cattle experienced 2.1 average daily gains over four months and protein content was double with the mixture. In a grass-only system with 60 pounds of applied nitrogen fertilizer, cattle experienced 1.7 pounds of average daily gain. Both systems were receiving similar amounts of moisture.
“For steers to gain weight, we need a protein content of at least 12.5% so the grass-only cattle were protein deficient because the grass was only 7% protein,” West said.
As far as water use per weight gain, for the alfalfa and grass mixture, it took 364 gallons per pound of gain versus 501 for the grass-only system.
“So it took 27% less water to produce a pound of gain when we had a legume compared to grass only,” West said. “High-quality alfalfa made all other inputs more efficient. Plus, no nitrogen fertilizer was applied to the alfalfa system.”
Additionally, the quality of the alfalfa meant that the other inputs were not being wasted. In the grass only scenario, quality was limiting the animal growth. When the value of added gain dollars per pound was calculated over five years, the alfalfa and grass system came out to $1.15 and grass only was $1.05. There was an added $0.10 gain with the alfalfa and grass pasture and part of that value from saving money on nitrogen.
The value of live weight gain dollars per acre for grass and alfalfa equaled $108, while grass only was $74. West said this varies with the market, because some years will show negative margins and other years will show a huge advantage with the alfalfa and grass system. However out of a five year span three of the years it was an advantage to use the alfalfa and grass combination. Although the grass and alfalfa pasture did receive slightly more water over the grass-only pasture, the water footprint was less with alfalfa.
In grass-only systems, production was 2,200 pounds per acre, versus alfalfa and grass with 28-inch row spacing that was 2,900 pounds per acre and alfalfa and grass in 14-inch spacing at 3,100 pounds per acre.
“So going to the higher density gives you very little advantage in forage productivity,” West said. “Low density gives you a large advantage.”
The grass-only forage was 62% digestible energy, alfalfa in 28-inch spacing was 68% digestible energy and 14-inch spacing was 71%. In addition, grass-only had 8% crude protein, 28-inch spaced alfalfa and grass was 13% crude protein and 14-inch alfalfa was 14%. Water depletion for grass only came out to 7 inches, 28-inch spaced alfalfa was 8 inches and it was 10 inches for 14-inch rows.
“The wide spacing gave us a big increase in forage quality and only a mild increase in amount of water depletion,” West explained. “Water use per pound of forage was 290 pound for grass-only, 240 for 28-inch alfalfa and grass and 230 pounds for 14-inch. Less rain water was used to produce a pound of forage where we had alfalfa in there.”
Low-density interseeding of alfalfa made large increases in forage yield and quality with fairly low trade-off in water depletion compared to high density planting. A modest amount of alfalfa in the system goes a long way toward improving native and non-native grass pastures and efficiency of converting water to forage and animal production.
“Alfalfa is the best legume option in low-input irrigated stocker pastures in the Texas High Plains when grown as a minority component with grasses,” West said. “A persistent hay-type alfalfa has potential in dryland and very low irrigated pastures on good water-holding soils. Use alfalfa on good soils where you can manage to avoid overgrazing. In a minority, we can get significant improvement in quality with only minimal changes in water intake.”
Lacey Newlin can be reached at 620-227-1871 or email@example.com.