Doctoral Dissertations

Date of Award

5-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant Sciences

Major Professor

Renata L. G. Nave Oakes

Committee Members

Renata L. G. Nave, Gary Bates, Chris Boyer, Harley D. Naumann

Abstract

Mixed pastures are known to produce greater biomass yields and higher nutritive value than monocultures. Intercropping biologically N fixating legumes, along with the use of intercropping warm-season annual grasses, such as crabgrass [Digitaria ciliaris Retz.], provides the potential to aid tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] productivity. To determine the benefits of intercropping species into tall fescue forage systems in the Southeastern U.S., two studies were developed. The first study consisted of 9 tall fescue paddocks, in which 3 paddocks contained red clover (Trifolium pratense L. [TRC]) mixed with tall fescue, 3 paddocks contained sunn hemp (Crotalaria juncea L. [TSH]) mixed with tall fescue, and 3 paddocks had only tall fescue with a late summer application of urea (TU). Black Angus steers [Bos taurus] were selected to graze the stockpiled paddocks during the grazing period. The study evaluated the botanical composition (BC), herbage mass (HM), nutritive value (NV), steer’s average daily gain (ADG), and net return (NR) values. In 2021, the TU treatment showed an overall greater amount of HM at the beginning of the grazing period and greater average CP values compared to the other treatments. The second experiment focused on aiding tall fescue productivity that consisted of tall fescue with no N source (TF-0), tall fescue mixed with red clover (TFR), tall fescue mixed with sunn hemp (TFS), tall fescue plus the application of ammonium nitrate (TFA), tall fescue mixed with crabgrass with no N source (TFC-0), tall fescue mixed with crabgrass and red clover (TFCR), tall fescue mixed with crabgrass and sunn hemp (TFCS), and tall fescue mixed with crabgrass plus the application of ammonium nitrate (TFCA). The study evaluated BC, HM, and NV. The plots containing red clover showed greater HM and crude protein (CP) values along with lesser NDF and NDFD48 values compared to the other treatments in 2020 and 2021. The TFCS plots showed approximately 38% greater herbage mass compared to TFS in 2020; approximately 32% greater HM in 2021. Suggesting the incorporation of cool and warm-season species with tall fescue can aid in tall fescue productivity.

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