Economic and Environmental Sustainability of Irrigated Grass-Legume Mixtures

Economic and Environmental Sustainability of Irrigated Grass-Legume Mixtures

Summary

The project is well-established and progressing very well. Following the same protocols as in 2014, the experimental plots were maintained at the University of Wyoming Sheridan Research and Extension Center in Sheridan, Wyoming. Likewise in 2014, the stands performed very well. Plots were harvested three times in 2015: first, second, and third harvest were made in June, August, and October, respectively. All forage samples were processed and analyzed for quality. Nitrogen fertilizer was applied in two-splits: early spring and late fall of 2015. Soil samples were collected for soil microbial, nutrients, and moisture content analyses. Additionally, soil moisture readings were taken three times from the installed neutron probes from each plot.

Data collected in 2014 and 2015 is being summarized and subjected to statistical analyses. In general, forage dry matter (DM) in mixture treatments was relatively lower than their respective sole stand treatments in 2014. An opposite trend in forage DM was observed in 2015. The highest yield (8580 kg ha^-1) was observed in 25% alfalfa + 25% birdsfoot trefoil + 50% meadow bromegrass treatment. Average forage yield was higher in 2015 (6854 kg ha^-1) than 2014 (4611 kg ha^-1), indicating clearly a well-established stand. Soil water depletion between April 4 and August 15, 2015 ranged from 301 to 318 mm. Water use efficiency ranged between 44 kg DM mm^-1 water (100% sainfoin; 50% sainfoin + 50% meadow bromegrass treatments) to 74 kg DM mm^-1 water (30% alfalfa + 70% meadow bromegrass treatment). Nutritive value of the legumes was higher than meadow bromegrass, and this resulted in higher nutritive value in meadow bromegrass-legume mixtures than sole meadow bromegrass with or without N application. Birdsfoot trefoil either grown in mixtures with alfalfa and meadow bromegrass or as monoculture shows potential along with alfalfa in Wyoming.

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Objectives/Performance Targets

1. Assess the effects of different ratios of grass-legume mixtures and nitrogen fertilizer rates on forage yield and quality;
2. Determine the effects of grass-legume mixtures on the persistence of legumes;
3. Assess the efficiency of water and nitrogen fertilizer use in the grass-legume mixtures cropping systems;
4. Determine the economic profitability of sole grass stands fertilized with nitrogen, sole legume stands, and grass-legume mixtures;
5. Evaluate the effects of grass-legume mixtures on soil organic matter buildup, pH, and microorganism populations.

Accomplishments/Milestones

Preliminary data of the study was presented in field days at Sheridan Research and Extension Center (2014 and 2015); in Western Alfalfa and Forage Symposium at Reno, Nevada (2015); and recently in Wyoming Forage Field Day at Sheridan (2016). The field plots were demonstrated to about 100 participants at the Wyoming Forage Field Day. Additionally, two field day bulletin articles and one proceedings article were published from the study.

Publications:

Adjesiwor, A.T. and Islam, M.A. 2015. Grass, legumes, and grass-legume mixtures: yield, nutritive value, and soil water use. In: Proceedings, 2015 Western Alfalfa & Forage Symposium Reno, Nevada December 3‐4, 2015. Western Alfalfa & Forage Symposium, 1521 I Street, Sacramento, CA 95814. (http://calhay.org/symposium/)

Adjesiwor, A.T., Islam, M.A., Jeliazkov, V., Ritten, J.P., and Garcia y Garcia, A. 2015. Productivity and Profitability of Irrigated Grass‐Legume Mixtures. 2015 Field Days Bulletin, University of Wyoming Agricultural Experiment Station, pp. 123-124. Available at http://www.uwyo.edu/uwexpstn/_files/docs/2015-field-days-bulletin.pdf.

Adjesiwor, A.T., Islam, M.A., Jeliazkov, V., Garcia y Garcia, A., and Ritten, J. 2014. Irrigated Grass-Legume Mixtures. 2014 Field Days Bulletin, University of Wyoming Agricultural Experiment Station, pp. 121-122. Available at http://www.uwyo.edu/uwexpstn/_files/docs/2014-field-days-bulletin.pdf.

Impacts and Contributions/Outcomes

Results of the study showed that birdsfoot trefoil has the potential to use as a good substitute for alfalfa in Wyoming. With the added benefits of non-bloating and resistance to the alfalfa weevil, birdsfoot trefoil will be suitable as a forage crop both for grazing and haying for Wyoming producers and perhaps for producers in neighboring states. Preliminary economic analysis showed that birdsfoot trefoil grown both in mixtures with meadow bromegrass and as a sole stand will be profitable.

Collaborators: