Short-term effects of repeated application of solid digestate on soil C and N dynamics and CO2 emission in a clay soil olive (Olea europaea L.) orchard

•Effects of repeated application of solid digestate were assessed in an olive orchard.•Single amendment with solid digestate produces significant legacy effects after one year.•Repeated application of solid digestate does not cause negative effect to the soil.•Repeated application compared to single application increases CO2 emission by 27%.•Over two-year application solid digestate determines growing benefits on soil fertility.