Legume grass mixtures reduce nitrogen requirements and production costs
October 16, 2013
Based on first-year data from a study by the University of Wyoming's Department of Plant Sciences, it appears that a 50-50 ratio of grass-legume mixture could increase yield, improve quality and reduce production costs (no use of nitrogen) in forage production systems.
A study initiated in 2011 at the James C. Hageman Sustainable Agriculture Research and Extension Center near Lingle, Wyo., sought to increase yield and quality of forage, reduce production costs and improve long-term profitability and sustainability of the forage production system by selecting an appropriate ratio of grass-legume mixture.
Two cool-season perennial grasses (meadow brome and orchard grass) and a legume (alfalfa) with different mixture ratios with two levels of nitrogen (zero and recommended dose at 134 pounds nitrogen per acre as urea) were used.
Sixteen treatments, including monoculture grass (with or without nitrogen), monoculture legume, two grass mixtures, one grass and one legume mixture, and two grasses and one legume mixture were used.
Grass-legume Mixtures increase forage Yield
First-harvest dry matter yield of forage ranged from 733 to 1,631 pounds per acre.
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Among the 16 treatments, yield was highest from treatment No. 9 (50-50 mixture of alfalfa and meadow brome).
The 50-50 (alfalfa and meadow brome) mixture produced greater forage yield than the nitrogen-added treatments.
The yield from all treatments increased in the second harvest and ranged from 1,143 to 2,625 pounds per acre.
The yield was highest from treatment No. 9 (50-50 mixture of alfalfa and meadow brome) and lowest from treatment No. 2 (100 percent orchard grass).
The dry matter yield again increased for all treatments in the third harvest and ranged from 1,892 to 4,812 pounds per acre.
Similar to previous harvests, the highest dry matter yield was obtained from treatment No. 9 (50-50 mixture of alfalfa and meadow brome).
Grass-legume Mixtures improve forage Quality
The crude protein content of forage ranged from 18 to 27 percent in the first harvest; was highest from treatment No. 11 (75-25 mixture of alfalfa and orchard grass); and lowest from treatment No. 1 (100 percent meadow brome).
Some grass-legume mixtures (50-50 mixture of alfalfa and orchard grass, 25-75 mixture of alfalfa and orchard grass) had similar crude protein content to 100 percent alfalfa.
The crude protein of forage varied from 18 to 28 percent in the second harvest and was highest from treatment No. 11 (75-25 mixture of alfalfa and orchard grass).
A similar trend was also found in the third harvest in terms of crude protein content and ranged from 15.5 to 26.9 percent.
This clearly indicates that legume in the grass mixtures improves forage quality.
Fiber content (both acid detergent fiber and neutral detergent fiber) was low in earlier harvests (first and second) compared to late harvest (third) and also in alfalfa monoculture and grass-legume mixtures.
highest forage, crude protein Yield
The study shows that 50-50 alfalfa and meadow brome has the highest forage and crude protein yield among the treatments.
In contrast, the highest forage quality was obtained from 75-25 alfalfa and orchard grass, indicating the superior quality of alfalfa and orchard grass compared to meadow brome.
The study is ongoing and will continue for at least two more years.
Researchers anticipate that results from this study will be useful to researchers and forage growers in the region in the long-term to improve profitability and sustainability of for- age production systems. ❖
This article appeared in most recent edition of the University of Wyoming College of Agriculture and Natural Science's magazine, Reflections, published annually by the Agricultural Experiment Station. To see the entire issue, go to http://www.uwyo.edu/uwexpstn/publications/reflections/.