Date of Award

12-2015

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant Sciences

Major Professor

Renata L. Nave Oakes

Committee Members

Patrick D. Keyser, Gary E. Bates, Travis Mulliniks

Abstract

Beef producers need drought tolerant options when selecting forage grasses and also practical methods to estimate forage nutritive value, which this study aims to provide for warm-season grasses. The objective of the first experiment was to develop estimates of warm-season forage nutritive value and herbage mass based on harvest timing. The experiment was conducted from 2013 to 2015 at the University of Tennessee Plateau AgResearch and Education Center (PREC) in Crossville, TN. Four species were evaluated, each for two years: bermudagrass [Cynodon dactylon (L.) Pers. cv. Vaughn’s # 1], switchgrass [Panicum virgatum (L.) cv. Alamo], sorghum-sudangrass [Sorghum bicolor (L.) Moench ×Sorghum Sudanese (P.) Stapf, cv. FSG208BMR], and crabgrass [Digitaria sanguinalis( L.) cv. Quick-N-Big]. Results indicate that there is a strong linear relationship between herbage mass and crude protein in both switchgrass and sorghum-sudangrass which could be used to estimate forage nutritive value based on herbage mass. The objective of the second experiment was to use water use efficiency (WUE) to evaluate the productive potential of grass species during limited rainfall. This experiment consisted of a greenhouse study followed by a field study. Water use efficiency data was collected through a greenhouse experiment held at The University of Tennessee, Knoxville. Species tested included crabgrass (Digitaria sanguinalis cv. ‘Red River’), switchgrass (Panicum virgatum (L.) cv. Alamo), big bluestem (Andropogon gerardii cv. ‘OZ-70’), indiangrass (Sorghastum nutans cv. ‘Rumsey’), eastern gamagrass (Tripsacum dactyloides cv. ‘Pete’), and bermudagrass (Cynodon dactylon cv. ‘Vaughn’s #1’). Results aided in forming hypotheses of species performance in the field. The field experiment took place at the Highland Rim AgResearch and Education Center (HRREC) in Springfield, Tennessee and the Ames Plantation (APREC) AgResearch and Education Center in Grand Junction, Tennessee during the growing seasons of 2014 and 2015. Results from the second experiment indicated that WUE of switchgrass and eastern gamagrass were greater than indiangrass and bigbluestem at APREC , but species did not differ at HRREC. In addition WUE differed with time of year at HRREC, but did not at APREC. Temperature and WUE were positively correlated at both locations suggesting that as temperature increases, WUE increases.

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