A global meta-analysis of livestock grazing impacts on soil properties

Abstract

Grazing effects on soil properties under different soil and environmental conditions across the globe are often controversial. Therefore, it is essential to evaluate the overall magnitude and direction of the grazing effects on soils. This global meta-analysis was conducted using the mixed model method to address the overall effects of grazing intensities (heavy, moderate, and light) on 15 soil properties based on 287 papers published globally from 2007 to 2019. Our findings showed that heavy grazing significantly increased the soil BD (11.3% relative un-grazing) and PR (52.5%) and reduced SOC (-10.8%), WC (-10.8%), NO 3-(-23.5%), and MBC (-27.9%) at 0-10 cm depth, and reduced SOC (-22.5%) and TN (-19.9%) at 10-30 cm depth. Moderate grazing significantly increased the BD (7.5%), PR (46.0%), and P (18.9%) (0-10 cm), and increased pH (4.1%) and decreased SOC (-16.4%), TN (-10.6%), and P (-23.9%) (10-30 cm). Light grazing significantly increased the SOC (10.8%) and NH 4 + (28.7%) (0-10 cm). Heavy grazing showed much higher mean probability (0.70) leading to overgrazing than the moderate (0.14) and light (0.10) grazing. These findings indicate that, globally, compared to un-grazing, heavy grazing significantly increased soil compaction and reduced SOC, NO 3-, and soil moisture. Moderate grazing significantly increased soil compaction and alkalinity and reduced SOC and TN. Light grazing significantly increased SOC and NH 4 +. Cattle grazing impacts on soil compaction, SOC, TN, and available K were higher than sheep grazing, but lower for PR. Climate significantly impacted grazing effects on SOM, TN, available P, NH 4 + , EC, CEC, and PR. Heavy grazing can be more detrimental to soil quality based on BD, SOC, TN, C: N, WC, and K than moderate and light grazing. However, global grazing intensities did not significantly impact most of the 15 soil properties, and the grazing effects on them had insignificant changes over the years.

Effects of Grazing on Water Erosion, Compaction and Infiltration on Grasslands

“…Lai and Kumar [40] (2020) analysed 287 papers about grazing impacts on soil properties from 2007 to 2019. They found that heavy and moderate grazing both caused a significant increase in bulk density and penetration resistance and a decrease in soil organic carbon and total nitrogen content in the 0-10 cm layer.…”

Optimizing Beef Cow-Calf Grazing across Missouri with an Emphasis on Protecting Ecosystem Services

“…Cattle grazing impacts on soil compaction, soil organic carbon, total nitrogen, and available potassium were greater than sheep grazing. Dahal et al [40] demonstrated that strategic grazing reduced nitrate runoff, whereas Schon et al [41] reported that proper grazing pressures increase earthworm populations.…”

“…The University Missouri Soil Health laboratory will perform the following health parameters: (i) total nitrogen and potentially mineralizable nitrogen, (ii) wet aggregate stability and bulk density, (iii) total organic carbon and active carbon, and (iv) phospholipid fatty acids. Perennial pastures may support soil health by (i) reducing erosion, (ii) accumulating soil organic matter, (iii) increasing macro and micropore space, and (iv) increasing the potential water availability for plant growth and development [39][40][41]. Moving cattle frequently, maintaining soil surface residue, avoiding grazing when soils are wet, and providing plant recovery after grazing are attractive attributes of a viable grazing program.…”

“…Excessive animal grazing creates soil compaction, erosion, nutrient depletion which leads to soil structure degradation, loss of soil carbon and nitrogen, reduced plant diversity and biomass, reduced microbial activity, increased soil acidity [36,37,[39][40][41]49,62]. However, conversion to rotational grazing alone will be insufficient to re-establish a full complement of ecosystem services.…”

Designing Grazing Susceptibility to Land Degradation Index (GSLDI) in Hilly Areas

“…Grazing, as a component of land use, is associated with certain patterns in hydrosedimentary conditions from event-scale to the catchment scale (e.g., Bartley et al, 2007;Rodriguez-Lloveras et al, 2015) and several studies have analyzed the relationship between unsustainable grazing, grassland status, and animal types (e.g., Warren et al, 1986;Mwendera and Saleem, 1997;Meyles et al, 2003;Pande and Yamamoto, 2006;Kidron, 2016;Pulley and Collins, 2019;Lai and Kumar, 2020). Unsustainable and prolonged grazing may trigger hydrological changes such as soil water content, but also the activation of runoff with an impact on the streamflow regime (e.g., maximum and minimum flow) affecting runoff coefficients (Gifford and Hawkins, 1978;Gifford et al, 1983;Markart et al, 2006;Sadeghi et al, 2007;Ruggenthaler et al, 2015), even with modifications of the terrestrial water (Vörösmarty and Sahagian, 2000).…”