Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Lemus, Rocky W.

Committee Member

Baldwin, Brian S.

Committee Member

Rivera, J. Daniel

Committee Member

Lang, David J.

Committee Member

Denny, Geoffrey C.

Other Advisors or Committee Members

Varco, Jac J.

Date of Degree

5-1-2018

Document Type

Dissertation - Open Access

Major

Agronomy

Degree Name

Doctor of Philosophy

Abstract

Alfalfa overseeded into warm-season perennial grasses such as bahiagrass or bermudagrass has the potential to increase forage quality and dry matter yield as well as extend the growing season. Many of the challenges associated with alfalfa in mixtures have been observed in warm-season grasses, but few studies have attempted to explain the dynamics between these grasses and alfalfa when grown together. Two studies were designed to note these relationships: The objective of the first study was to observe the effect of seeding rate and sod preparation on alfalfa and bermudagrass persistence over three years by using minimum tillage and alfalfa seeding rates of 17, 22, 28, and 39 kg ha-1. Results indicated that sod preparation had no effect on establishment compared to no-tillage. Seeding rates resulted in similar biomass yields and species composition by the second year suggesting that increased seeding rates were unnecessary. Forage quality and yield were improved throughout the year, but alfalfa composition generally decreased towards the end of summer. The objective of the second study was to quantify the amount of nitrogen recovered when alfalfa was overseeded into bahiagrass and bermudagrass and fertilized with ammonium nitrate during late summer. This was accomplished by using two nitrogen rates of 15N labeled fertilizer (28 and 56 kg N ha-1) and two application times (after 2nd and 3rd harvest) and in two separate planting environments (planting I and II). It was found that bahiagrass was more competitive than bermudagrass when overseeded with alfalfa. Alfalfa/grass mixtures did not increase forage dry matter yield, nutritive value or grass composition with N application. Nitrogen fertilizer recovery was variable between plantings due to a large variation of alfalfa persistence within different soil types. Where alfalfa was limited, grass fertilizer recovery was over 60%, but when grass composed less than 10% in the mix, then alfalfa had the potential to recover over 40% of the applied fertilizer. The greatest N recovery by grass were favored during late N application. On the other hand, alfalfa N recovery was favored by early fertilizer application.

URI

https://hdl.handle.net/11668/17654

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