Perennial alley cropping contributes to decrease soil CO2 and N2O emissions and increase soil carbon sequestration in a Mediterranean almond orchard

The implementation of alley cropping in orchards can be a sustainable strategy to increase farm productivity by crop
diversification and contribute to climate change mitigation. In this research, we evaluated the short-termeffect of alley
cropping with reduced tillage on soil CO2 and N2O emissions and soil total organic carbon (TOC) in an almond orchard
under Mediterranean rainfed conditions. We compared an almond monoculture with tillage in all plot surface (MC)
with almond crop with reduced tillage and growth of Capparis spinosa (D1) and almond crop with reduced tillage and
growth of Thymus hyemalis (D2). For two years, soil CO2 and N2O were measured, with soil sampling at the start and
end of the experimental period. Results showed that CO2 emission rates followed the soil temperature pattern, while
N2O emissions were not correlated with temperature nor moisture. Soil CO2 emissions were significantly higher in
MC(87mgm−2 h−1), with no significant differences between D1 and D2 (69mgm−2 h−1). Some peaks in CO2 effluxes
were observed after tillage operations during warm days. Soil N2Oemission rateswere not significantly different among
treatments. Cumulative CO2 and CO2 equivalent (CO2e) emissions were significantly highest in MC. When CO2e emissions
were expressed on a crop production basis, D2 showed the significantly lowest values (5080 g kg−1) compared to
D1 (50,419 g kg−1) and MC (87,836 g kg−1), owing to the high thyme yield, additional to the almond yield. No production
was obtained for C. spinosa, since at least two more years are required. TOC did not change with time in MCneither
D1, but it significantly increased inD2 from3.85 g kg−1 in 2019 to 4.62 g kg−1 in 2021. Thus, alley cropping can contribute
to increase the agroecosystem productivity and reduce CO2 emissions. However, it is necessary to grow