Nutritive Value of Switchgrass and Sudex As Influenced By Forage Management.

Warm-season grasses are competitive candidate species for grazing pastures in the Southern United States. Their high yielding and heat tolerant properties provide forage to grazing animals through the hottest months of summer, however they have lower nutritive values than cool-season grasses. In order to provide the best nutritive value possible, practical methods are needed to estimate nutritive value before cutting or grazing. The objective of this experiment is to develop practical, real-time, estimations of warm-season forage nutritive value that can be made easily by producers that will lead to better forage management practices and provide higher nutritive value throughout the summer. The experiment will be conducted during the 2013 and 2014 growing seasons at the University of Tennessee Plateau Research and Education Center in Crossville, TN. Two species will be evaluated: switchgrass -Panicum virgatum ‘Alamo’ and sudex -Sorghum bicolor ‘FSG208 BMR’. Species will be separately subjected to five treatments: June, July, August, and September cutting initiations and a height prescribed cutting. Monthly cutting will occur during the first week of each month and prescribed cutting will be implemented when swards reach 76.2 cm, cutting them to 20.3 cm. Each treatment will be replicated four times, in 13.9 m² plots, arranged in a completely randomized design with sub-sampling occurring weekly. Observations of visual morphological characteristics and data collected using Near-Infrared Spectroscopy will be used to analyze forage nutritive value in relation to cutting management. It is hypothesized that as herbage mass and age increase, forage nutritive value will decrease and that early cutting initiation dates followed by regular defoliation will lead to lower forage nutritive value across the growing-season. Regression analysis in SAS will be used to track and estimate weekly changes in nutritive value and compare 2013 and 2014 results.