Effect of dairy cattle production systems on sustaining soil organic carbon storage in grasslands of northern Spain

Abstract

Predicting the regional net greenhouse gas emissions (Net GHG) of grasslands is increasingly important, as these are one of the most globally widespread vegetation types, providing several ecosystem services. In this study, we assessed the regional soil organic carbon (SOC) change over a 30-year period (1981–2010), and the annual GHG balance for 405,000 ha of moist temperate Spanish grassland associated with dairy cow production. To do this we used the following: (i) an integrated modelling framework comprising geographic information systems (GIS); (ii) the RothC model to simulate SOC changes in managed grasslands under moist temperate conditions; and (iii) Tier 2 recent IPCC methods to estimate emissions. The results showed an average regional SOC change rate of 0.16 Mg C ha−1 year−1, associated with the initial SOC and livestock density. The annual GHG balance was positive, contributing to global warming by 5.6 Mg CO2-e ha−1 year−1. Livestock density was the main factor affecting net GHG emissions in the grasslands associated with dairy production in northern Spain. We determined a livestock density threshold of 0.95 LU ha−1, below which there is no SOC accumulation, and a threshold of approximately 0.4 LU ha−1, above which net GHG per livestock unit (LU) are reduced. In conclusion, our study confirms the importance of dairy cow grazing systems in preserving and/or enhancing SOC stocks in the grasslands of northern Spain. It is therefore crucial to optimise the livestock density considering large variety of feed intake and alternative manure management mitigation options to reduce the net GHG emissions. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.