Long-term effects of pasture management and fenced riparian buffers on soil organic carbon content and aggregation

Authors: XU, SUTIE - University Of Tennessee; JAGADAMMA, SINDHU - University Of Tennessee; Ashworth, Amanda; SINGH, SURENDRA - University Of Tennessee; Owens, Phillip; Moore, Philip

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2020
Publication Date: 9/16/2020
Publication URL: https://handle.nal.usda.gov/10113/7129844
Citation: Xu, S., Jagadamma, S., Ashworth, A.J., Singh, S., Owens, P.R., Moore Jr, P.A. 2020. Long-term effects of pasture management and fenced riparian buffers on soil organic carbon content and aggregation. Geoderma. 382. Article 114666. https://doi.org/10.1016/j.geoderma.2020.114666.
DOI: https://doi.org/10.1016/j.geoderma.2020.114666

Interpretive Summary: Soil organic carbon (SOC) is the greatest source of terrestrial carbon, therefore, SOC storage is considered a potential mitigation option for global climate change. Furthermore, grazing lands have considerable potential to sequester carbon globally, with over half this being attributed to improved grazing land management. Grazing activities can promote SOC accumulation via increased plant deposition following animal trampling. Overgrazing, however, can be detrimental to SOC accumulation, mainly because of reduced carbon sources from greater animal consumption. In addition, fertilizing pastures with poultry litter may enhance SOC accumulation due to nutrient additions spurring SOC formation. However, information is lacking on how best management practices (e.g. rotational grazing) alter soil aggregation and C protection, which also controls SOC stability. Therefore, a team of researchers measured various forms of SOC to determine how different pasture management practices influenced SOC dynamics after 13 years of continuous management. Researchers found that the conservation management practice (or rotational grazing) promoted the formation and storage of stable carbon in soils. This study also showed that cattle manure and poultry litter had a stronger effect on SOC accumulation than pasture management practices. Authors therefore recommend animal manure inputs (both poultry litter and cattle manure) and rotational grazing systems for increased stable carbon storage and ecosystem services.

Technical Abstract: Soil organic carbon (SOC) plays a key role in sustaining pasture agroecosystem function and its rate of accumulation can be influenced by management practices including manure deposition and grazing intensity. This study was conducted to determine the impacts of 13-years of different pasture management practices on SOC accumulation and aggregation. The field experiment consisted of five pasture management practices: (i) hayed (H), (ii) continuously grazed (CG), (iii) rotationally grazed (R), (iv) rotationally grazed with a grass buffer strip (RB), and (v) rotationally grazed with a fenced riparian buffer (RBR). Each treatment was replicated three times for a total of 15 watersheds. Starting from the top of hillslope, each watershed was divided into three landscape positions (A, B, and C). In addition, the fenced riparian buffer strip (RBS) at the bottom of the RBR watershed was also studied. Since 2004, all treatments received 5.6 Mg ha-1 of poultry litter annually except the buffer area. In general, soils in the landscape position A had greater SOC than RBS. However, permanganate oxidizable C was higher in all the pasture treatments compared to the RBS. Rotational grazing practice promoted the formation of large macroaggregates compared to other pasture management practices and RBS. All five pasture management treatments improved large macroaggregate-associated SOC content than RBS, and it was higher in grazed plots than the hayed plots. Overall, this study showed that organic manure input had a stronger effect on SOC accumulation and distribution compared to change in pasture management practices. We suggest a long-term monitoring at finer temporal- and spatial-scales to understand the interaction of pasture management strategies with organic inputs on accumulating SOC and providing ancillary ecosystem services.