Removing Grazing Pressure from a Native Pasture Decreases Soil Organic Carbon in Southern New South Wales, Australia

Abstract

Grazing management is a known influence of carbon accumulation in agricultural soil, but there is conflicting evidence on the extent. This study compared organic carbon and nitrogen stocks at the conclusion of a 5‐year grazing trial on a fertilised native pasture in south‐eastern Australia. The study included three grazing treatments: ungrazed, tactically grazed (set stocking with biannual rest periods) and cell grazed (intense stocking with frequent long rest periods). There was no influence of grazing treatment detected on pasture sward composition when averaged over seasons or on total nitrogen or bulk density. The cell grazing treatment had total carbon stock of 32·9 Mg C ha−1 (SE = 1·8) in the 0–0·30 m soil layer, which was a significant increase (p < 0·05) relative to the ungrazed treatment at 25·6 Mg C ha−1 but not statistically greater than the tactical treatment at 29·5 Mg C ha−1. There was no difference detected in labile carbon stocks to 0·30 m, which indicates that differences in soil carbon due to grazing was accumulated over the 5‐year trial rather than reflecting short‐term seasonal impacts. We propose that a combination of factors contributed to a greater stock of soil carbon under grazed pastures including differences in plant shoot/root allocation, root growth and root turnover with defoliation under grazing as well as lower plant productivity where grazing is excluded because of shading and nutrient tie‐up. This study demonstrates removing grazing pressure may lead to lower soil carbon stocks in native pastures over time and provides evidence of the potential for grazing management to increase soil carbon in the short‐term. Copyright © 2016 John Wiley & Sons, Ltd.

Long‐Term Grazing Alters Soil Trace Gas Fluxes from Grasslands in the Foothills of the Rocky Mountains, Canada

“…However, in the absence of a moderate cattle stocking rate, it is difficult to pin‐point the optimal role of grazing in this ecosystem. Soil organic C was not significantly affected by grazing intensity, which is consistent with some other studies (Kieft, ; Shrestha & Stahl, ; Li et al, ), but inconsistent with others (Orgill et al, ), which likely reflects site‐specific edaphic properties and environmental conditions.…”

Grassland Management Affects Delivery of Regulating and Supporting Ecosystem Services

“…In a South African mesic grassland, soils were 31 and 19% more compacted under the high-density method than conventional rotational stocking (low-density stocking), but the treatments did not differ in total soil C or total N (Chamane et al, 2017b). After 5 yr of grazing fertilized native pasture in southeastern Australia, there was no difference in pasture species composition, total soil N, or total C stock (0-to 30-cm layer) for continuous stocking with biannual rest periods compared with highdensity stocking with long rest periods (Orgill et al, 2018). In degraded South African rangeland, high-density, short-duration stocking increased SOC in the top 5-cm soil layer by an average of 12.4 g C m −2 yr −1 compared with 3.9 g C m −2 yr −1 in the typical continuous stocking management (Chaplot et al, 2016).…”

“…No difference in soil C (0-30 cm) between highdensity and continuous; high-density had greater C than ungrazed Orgill et al, 2018 to a 100-cm depth was 20% greater in pinto peanut (Arachis pintoi Krapov. & W.C.…”

Agricultural land abandonment in Mediterranean environment provides ecosystem services via soil carbon sequestration

“…The positive use of grasslands to restore degraded land and recover soil organic matter stocks has also been found in other regions, and the grasslands are very efficient even under grazing pressure (Lu et al, 2015;Orgill et al, 2016). The four Soil Regions were characterized by different IPCC factors (IPCCf i ) related to agricultural abandonment that ranged from 1.12 to 1.44 in SR1 and SR4, respectively (Table 1).…”