In this study, researchers wanted to understand the impact of vineyard grazing on soil organic carbon and underlying biochemical processes to develop best management practices for this growing management outlook. The authors looked to identify the benefits and trade-offs of re-introducing livestock to farming systems to decrease the dependency on fossil fuels (e.g. pesticides, mineral fertilisers and fuel) and sequester additional carbon in vineyard soils.
- Four sites were identified in Northern California where integrated sheep grazing was practised for more than ten years prior, and a suitable adjacent conventionally managed vineyard was present for comparison.
- Grazing practices were defined as high-density, short-duration rotational grazing. In practical terms, sheep grazing during vine dormancy, managed by electrical fencing, ~ 1-acre (0,4 ha) temporary paddocks, approximately 250 ewes grazing for 1-2 days, removing 80% of understory vegetation before rotating to the next temporary paddock.
- Soils were sampled at three depths (15cm, 30cm, 45cm) in the middle row before the termination events (grazing/integrated or mowing/conventional) and subjected to a series of analyses covering the following:
- Soil physio-chemical properties
- Soil microbial community
- Soil carbon flux and soil carbon storage pools
- Additional sites were added in a second sampling round to corroborate the initial findings.
- Grazing increased the quantities of active, labile, soluble soil carbon.
- Grazing stimulated microbial growth efficiency and biomass accumulation.
- Grazing increased inorganic soil nitrogen (N) and phosphorous (P) content.
- Grazing did not increase soil bulk density/compaction.
- Grazing increased mineral-associated organic carbon in the subsoil (45cm).
Significance of the study
Overall, the study’s findings show the strong potential of well-designed grazing systems to enhance soil functioning and increase soil organic carbon storage in vineyards in Mediterranean climates. The results shed light on the benefits of grazing, specifically in the realm of ‘soil health’ and potential mitigation strategies for climate change. However, it is important to note that this study did not focus on grapevine interactions; therefore, grazing-induced soil alterations and the resulting impact on yield and quality did not fall within the scope of this investigation.
Kelsey M Brewer, Mariana Muñoz-Araya, Ivan Martinez, Krista N Marshall, Amélie CM Gaudin, Long-term integrated crop-livestock grazing stimulates soil ecosystem carbon flux, increasing subsoil carbon storage in California perennial agroecosystems, Geoderma, Vol 438, 2023, 116598, ISSN 0016-7061, https://doi.org/10.1016/j.geoderma.2023.116598.
Photo credit: Etienne Terblanche