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Texas Tech University (2017)

Novel grazing management strategies for the southern high plains

Baxter, Lisa L.

Titre : Novel grazing management strategies for the southern high plains

Auteur : Baxter, Lisa L.

Université de soutenance : Texas Tech University

Grade : Doctor of Philosophy (PhD) 2017

Résumé
The imminent depletion of the Ogallala Aquifer demands innovative cropping alternatives to prevent dramatic losses of income when water levels are insufficient for irrigated row-crop production in the Southern High Plains. This research can help rejuvenate the region’s ranching heritage by promoting forage-based livestock systems that are potentially more productive and profitable than traditional rangelands, yet more water-frugal when integrated into a row-crop dominant ecosystem. Multiple research trials were conducted to investigate how selected novel grazing management strategies may optimize the sustainability and productivity of pasture-based beef stocker systems in the Southern High Plains, especially with respect to water use. The productivity and efficiency of a grass-legume pasture system employing novel forages and grazing techniques was compared to a grass only pasture system previously examined at the research site. The effect of legume inclusion on three water footprints of calculating water footprints of grass-based, beef stocker grazing systems with respect to stocker liveweight gain was determined. Five popular and novel nondestructive sampling techniques were compared in their ability to predict forage mass in tall wheatgrass-alfalfa pastures [TW, Thinopyrum ponticum (Podp.) ; Medicago sativa L. ; TW-alfalfa]. Finally, four nondestructive sampling techniques were compared to traditional botanical hand separations to determine their ability to predict legume content in TW-alfalfa and Old World bluestem-alfalfa yellow sweetclover pastures [OWB, Bothriochloa bladhii (Retz) S.T. Blake ; Melilotus officinalis L. ; OWB-legume]. Key research conclusions include : • Inclusion of legumes increased crude protein and improved forage quality. Longer, less frequent rotations into the protein bank resulted in higher ADG and translated to higher seasonal liveweight gain ha-1 in the grass-legume treatment in each trial year. • Inclusion of legumes reduced the water footprint of stocker grazing systems with respect to observed liveweight gains, despite water inputs. If rainfall was included in the calculation, the grass-legume system resulted in a lower water footprint ; whereas if rainfall was excluded, the inclusion of legumes increased the water footprint. • The PowerPoint® calibration model was the most precise option if restricted to a single sampling procedure, whereas the combined linear model (ImageJ + Height) would be more applicable since the inclusion of Height prevented saturation when predicted forage mass of TW-alfalfa pasture exceeded 1200 kg DM ha-1. • Nondestructive sampling procedures better predicted legume content in the OWB-legume pasture than the TW-alfalfa pasture as indicated by the higher R2pred values. Overall, predictive accuracy of the PowerPoint® model was best for OWB-legume pasture. The visual model possessed the highest R2pred while ImageJ best minimized predictive error in TW-alfalfa predictions. Overall, these novel grazing management strategies are promising in improving sustainable forage production here on the Southern High Plains.

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Page publiée le 23 octobre 2017