A Global Meta‐Analysis of Grazing Impacts on Soil Health Indicators

Abstract

Grazing lands support the livelihoods of millions of people across nearly one-half of the globe. Soils are the backbone of stability and resilience in these systems. To determine livestock grazing impacts on soil health, we conducted a global meta-analysis of soil organic carbon (SOC), total N, C/N ratio, and bulk density responses to grazing strategies (continuous, rotational, and no grazing) and intensities (heavy, moderate, and light grazing) from 64 studies around the world. Across all studies and grazing intensities, continuous grazing significantly reduced SOC, C/N, and total N compared with no grazing. Soil compaction (i.e., increased bulk density) was greater under both continuous and rotational grazing compared with no grazing; however, rotational grazing had lower bulk density than continuous grazing. Rotational grazing had greater SOC than continuous grazing and was not different from no grazing. The positive responses of SOC to rotational grazing could create climate change mitigation opportunities. Grazing strategy comparisons were minimally conditioned by aridity class (i.e., arid, subhumid, and humid); however, complete observations were notably limited or missing for many rotational grazing comparisons. For continuous and no grazing strategy comparisons, we found that grazing management can significantly influence soil function and health outcomes; however, site-specific environmental factors play important moderating roles. Greater coordination across regional, national, and global efforts, as well as consistent guidelines for soil health evaluation, would help overcome these knowledge gaps and vastly improve our collective understanding of grazing impacts on soil health, providing greater management and policy impacts.

Moderate grazing promotes the root biomass in Kobresia meadow on the northern Qinghai–Tibet Plateau

“…Many studies have documented how overgrazing can alter both pasture production and the composition and structure of grassland (Pulido, Schnabel, Lozano‐Parra, & González, ; Török et al, ; Tóth et al, ). For instance, the regenerative ability of grasslands was significant reduced, and the physical and chemical properties of soil were clearly altered (for example soil bulk density, soil water content and soil nutrients) following overgrazing (Byrnes, Eastburn, Tate, & Roche, ; Lin et al, ). There is growing evidence that soil bulk density and soil moisture content, respectively, increase and decrease significantly, after long‐term heavy grazing (Hofstede, ; Lu et al, ).…”

Measurements and Models to Identify Agroecosystem Practices That Enhance Soil Organic Carbon under Changing Climate

“…Dynamic process-based models to evaluate SOC † stocks Cavigelli et al (2018) Simulated Byrnes et al (2018) A Global Meta-Analysis of Grazing Impact on Soil Health Indicators Long-term field experiment Sherrod et al (2018) Soil Carbon Pools in Dryland Agroecosystems as Affected by Several Years of Drought † SOC, soil organic C.…”

“…In addition, the spatial assessments produced as part of the study could be used to reduce land degradation and restore degraded areas, which would be critical for climate change adaptation of these rangelands. Byrnes et al (2018) conducted a global meta-analysis of SOC, total N, C/N ratio, and bulk density responses to grazing intensities (heavy, moderate, and light grazing) and strategies (continuous, rotational, and no grazing) from 64 studies around the world to determine the impacts of livestock grazing on soil health. Across all studies and grazing intensities, continuous grazing significantly reduced SOC, C/N, and total N compared with no grazing.…”

Seasonal Hay Feeding for Cattle Production in the Fescue Belt

“…Incorporating other cool-and warm-season forages and grazing management practices into a tall fescue, cow-calf grazing system can also improve pasture conditions by reducing overgrazing and extending grazing days (Byrnes et al, 2018;Muir et al, 2011;Stanley et al, 2018). The diversification of forage for grazing systems allows producers to rest tall fescue pasture while grazing other forages.…”

“…The diversification of forage for grazing systems allows producers to rest tall fescue pasture while grazing other forages. Reducing overgrazing can reduce runoff and erosion leading to improvements in water quality and soil health (Byrnes et al, 2018;Muir et al, 2011). Rest periods also provide producers an opportunity to stockpile tall fescue forage growth during the fall for winter grazing, effectively extending grazing days and reducing fed hay costs (Ward et al, 2008).…”