Cattle farming and hay production are interrelated agricultural practices and the major economic contributors to the state of Wyoming.
According to Wyoming 2015 Agricultural Statistics, the cattle industry contributed 62 percent to the Wyoming agriculture economy with a total cash receipt of $937 million. On the other hand, hay contributed 67 percent of the total cash receipts for all crops in Wyoming, with a total cash receipt of $317 million. Among the different forage species, about 54 percent of the 1,060,000 acres planted for hay production was cultivated with grass, and the remaining was with alfalfa.
Grass hay producers in the state apply a significant amount of nitrogen (N) fertilizers to increase productivity. Chemical fertilizers, however, increase production costs and may degrade the soil and environment
if the fertilizers are not applied and managed carefully. Natural fertilizers such as legumes can fix free atmospheric N. Grass-legume mixtures could be a good alternative to reduce production costs and increase yield, quality, and stand persistence of forage crops; however, information is lacking on the optimum seeding mass ratios of grass-legume mixtures in Wyoming conditions.
Based on over three years’ study in Wyoming’s environments, there is clear evidence grass-legume mixtures have beneficial effects on forage productivity, quality, and stand persistence. There are numerous, unquantifiable environmental benefits as well. The 50-50 percent seeding mass ratio of grass-legume mixture performed very well and provided the following outcomes:
Grass-legume mixtures improve forage yield, quality, stand persistence
Dhruba Dhakal
Anowar Islam
Dhruba Dhakal, Department of Plant Sciences,
University of Wyoming, Laramie, WY 82071
Regional Agronomy Specialist, Northeast Region,
University of Missouri Extension, Keytesville, MO 65261
Anowar Islam, Associate Professor and Extension Forage Agroecologist, Department of Plant Sciences, University of Wyoming, Laramie, WY 82071
August 2017
B-1309.1
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Photo 2. Harvesting plots using custom-built research harvester at the James C. Hageman Sustainable Agriculture Research and Extension Center, Lingle, 2014.
Photo 1. Quadrat (20 inches × 20 inches) clipping to estimate the forage dry matter yield from the experiment at the James C. Hageman Sustainable Agriculture Research and Extension Center, Lingle, 2013.
Experimental Evidence
To obtain field-based information, an experiment was conducted from 2011-2014 at the James C. Hageman Sustainable Agriculture Research and Extension Center (SAREC) near Lingle to identify optimum seeding mass ratios of grass and legume for improved forage yields, quality, and stand persistence. The experiment consisted of 13 treatments with different seeding mass ratios of two grasses (‘Fleet’ meadow bromegrass and ‘Paiute’ orchardgrass) and one legume (‘WL 319 HQ’ alfalfa). The recommended seeding rates of alfalfa, meadow bromegrass and orchardgrass at 20, 20, and 6 pounds pure live seed (PLS refers to amount of live seed in bulk seed and is calculated multiplying seed purity percentage by seed germination percentage) per acre, respectively, were used. The treatments were repeated three times to collect precise information. Grass plots received either no N or 134 pounds N per acre as urea (Table 1). Plots were harvested three to four times each year from 2012 to 2014 (Photos 1 and 2). Forage dry matter (DM) yield was recorded and forage nutritive values were determined using near infrared reflectance spectroscopy (NIRS) at each harvest.
Grass-legume Effect on Forage Production
Variations were observed among the treatments for the total forage DM yield (Table 1). The 50-50 percent seeding mass ratios of meadow bromegrass-alfalfa provided the highest total forage DM yield followed by the 50-50 percent seeding mass ratios of orchardgrass-alfalfa with no N fertilizer application.
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Application of N fertilizer increased DM yields of monoculture grasses; however, these yields were lower than all seeding mass ratios of grasses and alfalfa. The 50-50 percent seeding mass ratios of meadow bromegrass and alfalfa produced 37 percent more forage yield than N applied (134 pounds N per acre) monoculture meadow bromegrass (29,260 vs. 21,378 pounds per acre), and 42 percent more than monoculture alfalfa (29,260 vs. 20,615 pounds per acre) over the three-year period. The higher yield from grass-legume mixtures than monoculture of either species was due to more efficient utilization of light, water, and nutrients. It was also due to mutual benefits from legume and grass in mixtures – legumes transferred fixed N to grasses and grasses reduced the hindering effect of soil N on biological N fixation by legumes.
Grass-legume Effect on Forage Nutritive Value
Grass-legume mixtures also affected forage nutritive values such as crude protein (CP), in vitro dry matter digestibility (IVDMD), acid detergent fiber (ADF), and neutral detergent fiber (NDF) contents during study period (Table 2).
In general, the CP and IVDMD of forage increased with increasing proportion of alfalfa in the mixtures. On the other hand, the ADF and NDF content of forage decreased with increasing proportion of alfalfa in the mixtures.
The N fertilizer application increased CP and IVDMD of grasses; however, these values were lesser compared to grass-legume seeding ratios containing at least 50 percent legume. Mixing legume with grass at least by 50 percent by seeding ratio also reduced ADF and NDF contents of forage compared to N fertilized monoculture grass. The total CP yield in three years from 50-50 percent seeding ratios of alfalfa and meadow bromegrass was 20 percent higher than monoculture alfalfa (6,847 vs. 5,689 pounds per acre).
Grass-legume Effect on Stand Persistence
Stand persistence of alfalfa in the mixtures was also determined during the three-years of study period. The proportion of alfalfa DM production was measured at each harvest in each year from all mixtures and analyzed for their changing pattern over the study period (data not shown). Among different treatments, the
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highest yielding 50-50 percent grass-legume seeding ratio of alfalfa-meadow bromegrass had constant alfalfa biomass proportion clearly indicating the persistent alfalfa stand during the study period (Photo 3).
Summary
Overall, there is positive impact of legumes on the mixed stands. At least 25 percent legume in the mixed stand can produce higher forage yield and quality than monoculture alfalfa and N fertilized grasses. The 50-50 percent would be an optimum seeding proportion of meadow bromegrass and alfalfa under Wyoming conditions for improved forage yield, forage quality, and stand persistence.
Issued in furtherance of extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Glen Whipple, director, University of Wyoming Extension, University of Wyoming, Laramie, Wyoming 82071.
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Photo 3. Plots with different seeding mass ratios of meadow bromegrass-alfalfa at the James C. Hageman Sustainable Agriculture Research and Extension Center, Lingle, 2014.
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100% meadow bromegrass with 134 pounds N per acre applied
25-75% seeding mass ratio of meadow bromegrass-alfalfa
50-50% seeding mass ratio of meadow bromegrass-alfalfa
100% alfalfa
References
Gebhart, D.L., C.A. Call, and R.W. Weaver. 1993. “Dinitrogen fixation and transfer in legume crested wheatgrass mixtures.” J. Range Manage. 46:431-435.
Mooso, G.D., and W.F. Wedin. 1990. “Yield dynamics of canopy components in alfalfa-grass mixtures.” Agron. J. 82:696-701.
WAS (Wyoming Agricultural Statistics). 2015. United States Department of Agriculture, National agricultural Statistics Service, Wyoming Field Office. p. 88.
Zhang, X., D.L. Mauzerall, E.A. Davidson, D.R. Kanter, and R. Cai. 2014. “The economic and environmental consequences of implementing nitrogen-efficient technologies and management practices in agriculture.” J. Environ. Qual. 44:312-324.