Abstract
Simple SummaryCanadian grasslands are recognized for providing high quality forage for grazing livestock and wildlife. The study was conducted on a re-established pasture in a Western Canadian semi-arid climate to investigate the effect of pasture species mixture and grazing management on pasture productivity, animal performance, and soil carbon sequestration. Pasture productivity and animal response were independent of pasture mixture but affected by grazing management. Average pasture dry matter productivity was greater with deferred-rotational grazing while pasture quality and animal gain were higher with continuous grazing. Soil carbon change varied with pasture seed mixture and grazing management interaction where pasture with 7-species mixture under continuous grazing had the lowest soil carbon gain. The objective of the study was to determine the effect of type of pasture mix and grazing management on pasture productivity, animal response and soil organic carbon (SOC) level. Pasture was established in 2001 on 16 paddocks of 2.1 ha that had been primarily in wheat and summer fallow. Treatments consisted of a completely randomized experimental design with two replicates: two pasture mixes (7-species (7-mix) and 12-species (12-mix)) and two grazing systems (continuous grazing (CG) and deferred-rotational grazing (DRG)). Pasture was stocked with commercial yearling Angus steers (Bos Taurus, 354 ± 13 kg) between 2005 and 2014. All pastures were grazed to an average utilization rate of 50% (40% to 60%). Average peak and pre-grazing pasture dry matter (DM) yield and animal response were independent of pasture seed mixture but varied with grazing management and production year. Average peak DM yield was 26.4% higher (p = 0.0003) for pasture under DRG relative to CG (1301 kg ha−1). However, total digestible nutrient for pasture under DRG was 4% lower (p < 0.0001) as compared to CG (60.2%). Average daily weight gain was 18% higher (p = 0.017) for CG than DRG (0.81 kg d−1), likely related to higher pasture quality under CG. Soil carbon sequestration was affected by seed mixture × grazing system interaction (p ≤ 0.004). Over the fourteen years of production, pasture with 7-mix under CG had the lowest (p < 0.01) average SOC stock at 15 cm (24.5 Mg ha−1) and 30 cm depth (42.3 Mg ha−1). Overall, the results from our study implied that increasing species diversity for pasture managed under CG may increase SOC gain while improving animal productivity.
Highlights
Native prairie grasslands are recognized as important resources in producing quality forage for Canadian beef production
Our study showed that pasture yield and quality and cattle performance were independent of native grass species mixture but varied with grazing management (CG and deferred-rotational grazing (DRG))
The increased pre-grazing pasture dry matter (DM) yield for DRG resulted in a greater stocking density but reduced pasture quality and animal performance
Summary
Native prairie grasslands are recognized as important resources in producing quality forage for Canadian beef production. Clayton et al [2] indicated that prior to their conversion into cropland, it is estimated that about 61.5 million ha of Canadian prairie soils were covered by native grassland vegetation. Given the diverse and essential ecological resources and services provided by native grasslands [3,4], there have been, over the past decades, several federal and provincial initiatives in Canada to revegetate marginal annual croplands to perennial forage production [5,6,7]. Management practices (e.g., grazing, burning, and fertilization) have been shown to influence carbon (C) sequestration of rangeland [8,10]. Improved grassland management practices that increase net accumulation of C in grasslands are gaining attention for their potential to minimize the rising concentration of atmospheric carbon dioxide
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