Carbon sequestration potential of residues of different types of cover crops in olive groves under mediterranean climate

The maintenance of plant cover between olive grove lanes until the beginning of spring is a soil management alternative that is gradually being adopted by olive growers. As well as protecting the soil from erosion, plant covers have other advantages such as improving the physicochemical properties of the soil, favouring its biodiversity and contributing towards the capturing of atmospheric carbon and its fixation in the soil. A trial was conducted over three growing seasons in an olive plantation situated in southern Spain. It was designed to evaluate the C fixation potential of the residues of the cover species Brachypodium distachyon, Eruca vesicaria, Sinapis alba and of spontaneous weeds; and also to study the decomposition dynamics of plant residues after mowing cover. After 156 and 171 days of decomposition, the species that released the largest amount of C was Brachypodium with values of 2,157 and 1,666 kg ha(-1) respectively, while the lowest values of 461 and 509 kg ha(-1) were obtained by spontaneous weeds. During the third season (163 days of decomposition) and due to the weather conditions restricting the emergence and growth of cover, spontaneous weeds released the most C with a value of 1,494 kg ha(-1). With respect to the fixation of C, Sinapis records the best results with an increase in soil organic C (SOC) concentration of 7,690 kg ha(-1). Considering the three seasons and a depth of 20 cm, the behaviour sequence of the different species in favouring the fixation of soil organic C was Sinapis > Brachypodium > spontaneous weeds > Eruca.