|GELLEY, CHRISTINE - The Ohio State University|
|KEYSER, PATRICK - University Of Tennessee|
|NAVE, RENATA - University Of Tennessee|
|RHINEHART, JUSTIN - University Of Tennessee|
Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2020
Publication Date: 9/12/2020
Citation: Gelley, C.H., Ashworth, A.J., Keyser, P.D., Nave, R., Rhinehart, J. 2020. Water-Use efficiency of forage crops in the Southeastern United States. Agronomy. 10(9):1377. https://doi.org/10.3390/agronomy10091377.
Interpretive Summary: The Southeastern United States has been subjected to multiple severe droughts during the past decade and climatologists expect this trend to continue. Increasing the use of warm-season forages may minimize impacts of future droughts and assist in maintaining beef production, which is the United States’ largest agricultural sector. However, it remains unclear which warm-season forages are the most efficient water users under water-limited conditions. ARS and University Researchers evaluated water-use efficiencies of eight forages in a greenhouse and in-field study under grazing conditions. Their study concluded that the native warm-season grass switchgrass was among the most efficient user of water, as was crabgrass (which is an introduced forage). Study results can help producers select more drought tolerant species in grazing systems of the Southeast.
Technical Abstract: In recent years, livestock producers in the southeastern United States have experienced increasingly variable weather patterns throughout the growing-season, thus altering management of integrated crop-livestock systems. Preparing producers to cope with volatile changes in weather, specifically drought, requires a better understanding of forage water-use efficiency (WUE) potentials. This experiment’s objective was to initially measure WUE through real-time gas exchange measurements of photosynthesis and transpiration to evaluate forage productive potential in a 1) greenhouse study where drought was enforced and later 2) under in-field grazing conditions. Both instantaneous water use efficiency (iWUE) and mass based WUE (mWUE) data were collected. Under Study 1, species tested included: crabgrass (CG; Digitaria sanguinalis cv. ‘Red River’), switchgrass (SG; Panicum virgatum cv. ‘Alamo’), big bluestem (BB; Andropogon gerardii cv. ‘OZ-70’), indiangrass (Sorghastum nutans cv. ‘Rumsey’), eastern gamagrass (EG; Tripsacum dactyloides cv. ‘Pete’), bermudagrass (Cynodon dactylon cv. ‘Vaughn’s #1’), sorghum-sudangrass [Sorghum bicolor (L.) ×Sorghum sudanese (P.) cv. ‘Greengrazer’] and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort]. Imposed drought in Study 1 did not impact iWUE rates of tested species, but differences between species were observed (P=0.05). Crabgrass responded similarly to drought as native warm-season grasses and was selected for the larger field experiment. Study 2 occurred at Highland Rim AgResearch and Education Center (HRREC) in Springfield, Tennessee and Ames Plantation (APREC) AgResearch and Education Center in Grand Junction, Tennessee during three growing-seasons (2014- 2016) and evaluated CG, SG, BG, EG, and BB. Overall, in situ iWUE of CG, SG, EG, and BG did not differ (P=0.05), while iWUE of big bluestem and indiangrass were less drought tolerant than SG and CG. Study results can help producers select more drought tolerant species in grazing systems of the Southeast.