Continuous grazing of mixed native warm‐season grass in the fescue belt

Abstract

Continuous, season-long (May-August) grazing is the most commonly used grazing strategy among tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] belt beef (Bos taurus) producers. However, little information is available regarding the feasibility of managing native warm-season grass (NWSG) pastures in this region with continuous, season-long grazing. We compared stand sustainability, beef cattle performance, and pasture production between continuous (CONT), season-long grazing and heavy-early (HEAVY), a modified continuous grazing strategy, on mixed-NWSG pastures. Heavy-early was designed to match the growth curve of NWSG, with an initial stocking target of 1.25 times the CONT density until 25 June, at which time stocking was reduced to 0.75 times the CONT density. Pastures were mixed big bluestem (Andropogon gerardii Vitman), indiangrass [Sorghastrum nutans (L.) Nash], and little bluestem [Schizachyrium scoparium (Michx.)]. The plant population (plants m −2) was similar between treatments, but years differed (P < .001), with a 35% reduction from 2017, the third and final year of grazing, to 2018. Despite the decline in plant density, overall tiller density (tillers m −2) increased 14%, indicating that the grazing strategies were likely sustainable. The grazing strategies had similar (P > .05) average daily gain (ADG; kg d −1), animal-days ha −1 , and total gain (kg ha −1). Weaned steer ADG was 0.98 kg d −1 for CONT and 0.89 kg d −1 for HEAVY. Total gain was 379 kg ha −1 for CONT and 334 kg ha −1 for HEAVY. Continuous grazing appears to be an appropriate strategy for managing NWSG pastures in the Fescue Belt.

Forage production and persistence characteristics of grazed native warm‐season grass mixtures with or without nitrogen fertilizer

“…CP concentration and IVTD were less than values reported for big bluestem, little bluestem, and indiangrass mixtures under clipping studies or grazing evaluations by 2-4 percentage points (Backus et al, 2017;Brazil et al, 2020;Rushing et al, 2019Rushing et al, , 2020. Differences in forage nutritive value responses among these studies and the present trial may be due to relative canopy height and stage of maturity of NWSG during the first 30 days of defoliation management.…”

“…The response of NWSGs in monoculture or mixtures to N fertilization is well reported in the literature under clipping, bioenergy, or hay production systems (Angima et al, 2009; Duran et al, 2016; Lowe et al, 2015; Popp et al, 2018; Waramit et al, 2011, 2012), with generally increased forage mass observed with seasonal N application rates of up to 168 kg N ha −1 . Forage production responses of NWSG to N fertilizer application rates under grazing are more limited (B. Anderson et al, 1988; Berg, 1995; Gillen & Berg, 1998), especially in NWSG mixed species swards (Backus et al, 2017; Brazil et al, 2020; Rushing et al, 2020). Backus et al (2017) evaluated NWSG monocultures or mixtures of big bluestem and indiangrass under continuous stocking using a similar N fertilization strategy as in the present trial with an annual spring application of 67 kg N ha −1 .…”

“…Pastures in their evaluation were initially stocked at a rate of 1245 and 953 kg of animal BW per hectare in Year 1 and Year 2 of the study, respectively. Whereas early‐season forage growth of NWSG mixtures may initially support greater stocking densities (Brazil et al, 2020), adjustments to lower stocking densities on NWSG by mid‐to‐late season have been reported in the literature and coincide with the slower growth rate of NWSG as the season progresses (Backus et al, 2017; Brazil et al, 2020; Rushing et al, 2020). Nitrogen fertilization at rates used in the present study may support greater initial stocking, but adjustments in stocking management should be made during the subsequent months of the growing season to reduce grazing pressure and the potential for overgrazing (Backus et al, 2017; Brazil et al, 2020).…”

“…Forage production responses of NWSG to N fertilizer application rates under grazing are more limited (B. Anderson et al, 1988;Berg, 1995;Gillen & Berg, 1998), especially in NWSG mixed species swards (Backus et al, 2017;Brazil et al, 2020;Rushing et al, 2020). Backus et al (2017) evaluated NWSG monocultures or mixtures of big bluestem and indiangrass under continuous stocking using a similar N fertilization strategy as in the present trial with an annual spring application of 67 kg N ha −1 .…”

“…Whereas several trials in the continental United States have evaluated NWSG monocultures or mixtures and their forage growth response to N fertilization for hay, bioenergy crop production, or dual-purpose use with grazing (Angima et al, 2009;Backus et al, 2017;Duran et al, 2016;Lowe et al, 2015;Popp et al, 2018;Waramit et al, 2011Waramit et al, , 2012Waramit et al, , 2014, few studies have evaluated N-input strategies for full-season grazing of NWSG mixtures to characterize system-level forage responses under these conditions (Boyer et al, 2020;Brazil et al, 2020;Keyser et al, 2016). Brazil et al (2020) noted that adoption of NWSG in the southeastern United States has been relatively slow and that evaluation of forage and animal management practices, which more closely mimic labor and input willingness of farmers, may help demonstrate the feasibility of NWSG in the region. This information can be used to guide on-farm recommendations to forage-livestock operators who may consider NWSG as an alternative, warm-season perennial forage option given shifts in N fertilizer-use dynamics.…”