Nitrogen Use Efficiency of Cool-Season Perennial Forage Grasses Planted With and Without Alfalfa Under Irrigation for Hay Production

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2008: $14,999.00
Projected End Date: 12/31/2010
Region: Western
State: Wyoming
Principal Investigator:
Dr. Blaine Horn
University of Wyoming

Annual Reports


  • Agronomic: general hay and forage crops, grass (misc. perennial), hay


  • Animal Production: feed/forage
  • Crop Production: nutrient cycling, application rate management, tissue analysis
  • Production Systems: general crop production
  • Soil Management: soil analysis


    ‘NewHy’ hybrid wheatgrass and ‘Oahe’ intermediate wheatgrass produced the most hay with no applied nitrogen, and ‘Paiute’ orchard grass produced the least. ‘Manchar’ smooth bromegrass produced more hay per pound of nitrogen than the other grasses in 2011, whereas ‘Luna’ intermediate wheatgrass did so in 2010. However, the greatest net income at all nitrogen rates was obtained with ‘Oahe’. To ensure grass hay crude protein content is sufficient for a lactating beef cow, the grass should be fertilized with at least 50 pounds of nitrogen per acre. However, at rates above 100 pounds per acre high nitrate-nitrogen content can result.


    Alfalfa produces high quality hay of good yields, but stands can be short-lived, resulting in high establishment costs and increased potential for soil erosion due to tillage. In addition, weed control options are limited, and insect, nematode and disease infestations can increase production costs and reduce yields. Alfalfa also can cause bloat in ruminant livestock and, after a hard fall freeze, few leaves are left on the stems for grazing.

    Cool season grasses can produce respectable hay yields in the Western U.S., potentially for more years than alfalfa, and generally have less weed, insect, nematode and disease problems, reducing pesticide need, thus protecting the health and safety of agricultural workers. In addition, grass hay fields should maintain or enhance soil quality and productivity, as well as maintain or improve water quality.

    Diversifying haying operations with cool season grasses could provide agricultural producers more management flexibility, increasing sustainability of their operations. Cool season grass hay fields could be grazed in the spring and yet produce a respectable hay crop. In addition, they could be grazed throughout the summer if needed or in the fall, after livestock are taken off native range pastures. This could greatly benefit Western U.S. ranchers, especially during drought, by providing growing season rest to their native range pastures.

    Thus cool season grasses for hay production could enhance the quality of life of Western U.S. agricultural producers by reducing hay production costs (establishment and pest control), increasing management flexibility and improving land stewardship. If so, the viability of Western U.S. agricultural communities would be maintained, as these lands would remain in agricultural production instead of being sub-divided.

    With rising energy costs and high fertilizer prices, it is imperative that irrigated cool season grass hay fields be managed for optimum forage production. Cool season grasses require nitrogen (N) fertilization to produce comparable yields to alfalfa and to maintain stand health and longevity. Thus N fertilizer management by Western U.S. hay producers will be important for stewardship and sustainability of their grass hay lands. Fertilizer recommendations based on a soil test for cool season perennial forage grasses are the same regardless of species. However, some of these grasses may be more nutrient use efficient with respect to N and produce more forage on less N fertilizer. If there are cool season grasses that are more N use efficient, producers could potentially lower their N fertilizer use and resultant costs without sacrificing hay yields and stand longevity.

    Project objectives:

    1) Compare forage yields of cool season perennial grasses under irrigation.

    2) Compare nitrogen use efficiency (NUE) of cool season perennial grasses (soil residual nitrate levels and forage yields per lb N fertilizer).

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.