Using Annual Forages to Replace Declining Cool-Season Grass Pasture Availability

Authors

Jonathon Matthew Jenkins, University of Nebraska-LincolnFollow

First Advisor

John A. Guretzky

Second Advisor

Daren D. Redfearn

Third Advisor

Mary E. Drewnoski

Date of this Version

5-3-2024

Document Type

Thesis

Citation

Presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Agronomy

Under the supervision of Professor John Guretzky

Lincoln, Nebraska, May 2024

Comments

Copyright 2024, Jonathan Matthew Jenkins. Used by permission

Abstract

As land area in grain crop production increases in the US Midwest, perennial pasture availability decreases but the demand increases. Matching the seasonal growth patterns of C₃ and C₄ plant species to grow forages that are complementary allows producers to fill production gaps in otherwise monoculture systems and possibly increase overall productivity. One way to fill the forage production gap of C₃ grass dominated pastures is by producing a warm-season, annual forage in a separate field. However, with continual reductions in land availability, this may not be an option. Using two studies, our objectives were to improve forage crop production within existing perennial pastures and in historical cropland converted to annual pastures. We also wanted to compare the effects of N fertilized grass monocultures to non-N fertilized grasses mixed with legumes to see if N fertilization could be replaced by legumes. To improve the total forage production within smooth bromegrass pastures, we sod-seeded sorghum × sudangrass but found too large a reduction in smooth bromegrass forage mass the following year with no improvement in forage production. To sustainably improve forage production and distribution within land area under annual forage production, we tested the viability of a double cropped forage system using fall planted triticale cut once in the spring followed by pearl millet cut once in the summer and compared it to a perennial system containing smooth bromegrass. We found that timely precipitation was crucial to the success of the annual system and when abundant, the double cropped annual forage system produced most of the forage during the summer. This contrasts with smooth bromegrass pastures, which produced the greatest during the spring. Nitrogen fertilization and mixed grass-legume produced similar forage mass in smooth bromegrass pastures, but mixed grass-legume pastures produced less mass in the annual forage system.