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Cover crops can perform multiple ecosystem functions, including weed control, soil quality enhancement and support to pollinators. While the contribution of individual cover crop species or mixtures to each of these functions has been extensively investigated, experiments testing all these ecosystem functions simultaneously to select the best species or mixture overall are rare. In this study, we evaluated the performance of six summer cover crop species in terms of biomass production, weed suppression, soil fertility enhancement potential and support to wild and managed pollinators. Tested species included buckwheat (Fagopyrum esculentum Moench.), white mustard (Sinapis alba L.), berseem clover (Trifolium alexandrinum L.), blue tansy (Phacelia tanacetifolia Benth.), fenugreek (Trigonella foenum-graecum L.) and common vetch (Vicia sativa L.). Field work was carried out in four fields in Northern Italy during the summer months of 2020 and 2021. Buckwheat was identified as the overall best-performing species, by virtue of its high biomass production, ability to control weed growth, and abundant and long-lasting flowering that could support honeybees and hoverflies during a low-resource period without promoting competition. Buckwheat was, however, less promising regarding soil enhancement potential and support to wild bees, highlighting the need to continue searching for complementary cover crop species to be used alongside it in a mixture. Our results could improve cover crop selection schemes, suggesting the necessity for a comprehensive approach aimed at enhancing multiple ecosystem functions in agroecosystems. • Buckwheat was the best cover crop in terms of biomass production and weed control. • Buckwheat can support honeybees and hoverflies without promoting competition. • Buckwheat is lacking in terms of soil quality enhancement and support to wild bees. • Other cover crop species complementary to buckwheat should be considered. • An evaluation approach based on multiple functions might improve crop selection. [ABSTRACT FROM AUTHOR]

Carbon sequestration in soil has been extensively sought in the agroecosystems through practices which increase organic carbon inputs and/or decrease soil organic carbon (SOC) degradation processes. Less is known about the extent of shallow water table influences in mineral soils, despite being soil moisture a major driver in modifying the C cycle. To examine its effects, a 4-yr lysimetric experiment was set up to measure the C balance components under free drainage and shallow water table at 60 and 120 cm depth. Two levels of N input (250 and 368 kg N ha−1 y−1) were also studied, using dry manure in 2011 and 2012 and fresh manure in 2013 and 2014. Carbon balance was estimated through the difference between inputs (C from organic inputs and root residues and exudates) and outputs (heterotrophic respiration, methane, and C leaching). A negative C balance was measured under all treatments (−3487 kg C ha-1), being respiration not compensated by the consistent C input of organic fertilizer. Furthermore, high N inputs increased SOC mineralization, decreasing the C balance. The role of soil was also observed by the SOC analyses, which confirmed the losses estimated through C balance. The study substantiated also the interacting effect between shallow water table and type of organic carbon, which was revealed crucial for C balance in mineral soils. To conclude, results suggested that water table level around 120-cm depth could limit SOC depletion. • C depletion over a 4-yr period was higher at high N inputs. • WFPS effect on CO2 emissions depended on amount of recalcitrant C in fertilizer. • C roots and heterotrophic respiration were pivotal. • C leaching and methane emission were negligible. • Maintaining water table level around 120-cm depth could limit SOC depletion. [ABSTRACT FROM AUTHOR]

A new principle for measuring soil CO2 efflux at constant ambient concentration is introduced. The measuring principle relies on the continuous absorption of CO2 within the system to achieve a constant CO2 concentration inside the soil chamber at ambient level, thus balancing the amount of CO2 entering the soil chamber by diffusion from the soil. We report results that show reliable soil CO2 efflux measurements with the new system. The novel measuring principle does not disturb the natural gradient of CO2 within the soil, while allowing for continuous capture of the CO2 released from the soil. It therefore holds great potential for application in simultaneous measurements of soil CO2 efflux and its δ13C, since both variables show sensitivity to a distortion of the soil CO2 profile commonly found in conventional chamber techniques. [Copyright &y& Elsevier]