Soil management and compost amendment are the main drivers of carbon sequestration in rainfed olive trees agroecosystems: An evaluation of chemical and biological markers

11 páginas.- 10 figuras.- 2 tablas.- referencias.- Supplementary data to this article can be found online a https://doi.org/10.1016/j.catena.2022.106258

Traditional olive groves are considered at high risk of erosion and desertification due to low organic matter inputs and scarce vegetation cover coupled to highly intensity tillage, leading to a further decrease in soil organic carbon contents. In a context of climate change, carbon sequestration through waste management in the framework of a circular economy becomes of primary importance for rainfed Mediterranean agricultural soils. To unveil the mechanisms of carbon sequestration in those agroecosystems, we evaluated the effect of the application of two composts (olive waste “alperujo” and biosolid) at two different doses coupled to the sustainable soil management allowing spontaneous vegetation growing on the soil surface. With this aim, solid state nuclear magnetic resonance was used to trace the evolution of the chemical composition of compost-derived and soil-derived organic matter. Successively, the activity of soil microbial community after the compost addition was monitored by measuring two enzymatic activities (β-glucosidase and dehydrogenase) and soil CO2 respiration. Lastly, the adaptation of microbial communities was quantified using the genes encoding soil enzymes associated with C cycling -glucosidase and laccase-like multicopper oxidases. The results of this study show that biosolid compost has a higher potential for C storage at mid-term (24 to 30 months after first application) than alperujo compost, yielding up to 50% net C sequestration in the topsoil in addition to the compost-derived C applied. We attribute these results to biosolid compost chemical composition, closer to that of the native organic matter, which led to a less abrupt adaptation of soil microbial functioning (lower flushes of water soluble C, lower number of copies of genes encoding enzymatic activities) to the new C source, if compared to alperujo compost. The results encourage the reduction of soil perturbation and the use of organic amendments instead of mineral fertilizers to increase carbon storage and improve sustainability of olive groves in the Mediterranean agroecosystems.

This study was financially supported by the the Spanish Ministry of Science, Innovation and Universities [project number AGL2017-84745] and European FEDER funds. Research activity of Dr. M. Panettieri has been funded by Spanish Ministry of Science, Innovation and Universities post-doctoral fellowship [grant number IJCI-2016-27693] and Comunidad de Madrid and the Spanish National Council of Scientific Researches research grant Atraccion de Talento [grant number 2019T1/ AMB14503]. Research activity of Dr. Laura L. de Sosa has been funded through the Junta Andalucía and European Union for the research grant awarded in the area of the Andalusian Research, Development and M. Panettieri et al. Innovation [PAIDI 2020]

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