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Simple Summary: Farming systems in which no-till (NT) and cover crops (CC) are preferred as alternatives to conventional practices have the promise of being more resilient and climate smart. Our field study aimed to assess the long-term impact of NT plus CC, with vs. without short-term water stress, on soil microbial biodiversity, enzymatic activities, and the distribution of C and N pools within soil aggregates. We found that the diversity of bacteria and fungi in the soil was positively affected by NT + CC, especially under water stress conditions. Under NT + CC, the presence of important plant growth-promoting rhizobacteria was revealed. Soil enzymatic activity confirmed the depleting impact of conventional tillage. Soil C and N were increased under NT + CC due to their inclusion into large soil aggregates that are beneficial for long-term C and N stabilization in soils. Water stress was found to have detrimental effects on aggregates formation and limited C and N inclusion within aggregates. The microbiological and physicochemical parameters correlation supported the hypothesis that long-term NT + CC is a valuable strategy for sustainable agroecosystems, due to its contribution to soil C and N stabilization while enhancing the biodiversity and enzymes. Combining no-till and cover crops (NT + CC) as an alternative to conventional tillage (CT) is generating interest to build-up farming systems' resilience while promoting climate change adaptation in agriculture. Our field study aimed to assess the impact of long-term NT + CC management and short-term water stress on soil microbial communities, enzymatic activities, and the distribution of C and N within soil aggregates. High-throughput sequencing (HTS) revealed the positive impact of NT + CC on microbial biodiversity, especially under water stress conditions, with the presence of important rhizobacteria (e.g., Bradyrhizobium spp.). An alteration index based on soil enzymes confirmed soil depletion under CT. C and N pools within aggregates showed an enrichment under NT + CC mostly due to C and N-rich large macroaggregates (LM), accounting for 44% and 33% of the total soil C and N. Within LM, C and N pools were associated to microaggregates within macroaggregates (mM), which are beneficial for long-term C and N stabilization in soils. Water stress had detrimental effects on aggregate formation and limited C and N inclusion within aggregates. The microbiological and physicochemical parameters correlation supported the hypothesis that long-term NT + CC is a promising alternative to CT, due to the contribution to soil C and N stabilization while enhancing the biodiversity and enzymes. [ABSTRACT FROM AUTHOR]

• No-till (NT) with cover crops (CCs) maintains yield of wheat, maize and soybean. • NT-CCs increased SOM from 20% to 30% compared to CT in the 0-30 cm soil layer. • NT-CCs increased STN from 21% to 28% compared to CT in the 0-30 cm soil layer. • Replacing CT with NT and winter CCs enhances soil fertility in the long-term. Introducing no-till and cover crops in arable agro-ecosystems leads to the restoration of soil fertility, through the increase of soil organic matter (SOM), soil total nitrogen (STN), and available phosphorus (P), therefore maintaining or enhancing crop yield and reducing costs. Although the effects of those practices have been widely examined, many studies show conflicting results and little is known about the combined effects of no-till (NT) and cover crops (CCs) under intensive arable cropland in the Po Valley (Northern Italy). The objectives of this study were: (i) to evaluate if NT management coupled with CCs negatively affects yields during the transition period and how yields evolve; (ii) to assess SOM, STN, and P dynamics in the 60-cm soil depth layer; and (iii) to evaluate the effects of different types of winter cover crops on yield and soil parameters. A six-year field experiment was established in Piacenza, on a silty-clay soil under temperate climate conditions. The crop sequence was: winter wheat, maize, maize, soybean, winter wheat, and maize. The four experimental treatments were: (1) conventional tillage (CT) as control; (2) NT with CC of rye (NT-R); (3) NT with CC of hairy vetch (NT-V); and (4) NT with a mixture of CCs (rye, hairy vetch, crimson clover, Italian rye-grass and radish) [NT-M]). Dry biomass yield of CCs ranged between 2.2 and 3.1 Mg ha−1 for rye; 1.9 and 3.0 Mg ha−1 for hairy vetch; and 1.9 and 3.2 Mg ha−1 for mixture. In the present study, yields of winter wheat, maize, and soybean were generally not reduced with NT-CCs since the first year after conversion. The different composition and thickness of cover crop mulch showed an opposite yield response to rainfall pattern: under NT-R, a negative correlation was observed between grain yield and rainfall, while under NT-V this correlation was positive. After six years, SOM and STN concentrations in the 0-30 cm soil layer increased in NT-CCs. SOM concentration was +30%, +23% and +20% higher than CT for NT-R, NT-M and NT-V, respectively. STN was +28% higher under NT-R and NT-V, and +21% higher under NT-M, than CT. Conversely, P concentration was not influenced by the NT-CCs system, although we observed a tendency to increase under NT-V. In the 30-60 cm soil, layer, the tillage systems did not affect SOM and STN. We concluded that introducing NT with winter CCs into intensive arable agricultural systems is an effective strategy for enhancing soil fertility in fine-textured soils under temperate climates, without penalizing yields. [ABSTRACT FROM AUTHOR]

• Minimum tillage (MT) increased grain yield (+7%) in an 8-year maize monoculture. • Maize yield was reduced by no-till (NT) during the initial 5 years, while increased afterwards. • NT and MT increased C sequestration by 1.45 and 1.52 Mg ha−1 yr−1 compared with CT. • C and N associated to microaggregates within macroaggregates accounted for 41–65 % of total soil C and N under NT and MT. Intensive management of agroecosystems has been widely indicated as major responsible for soil degradation, thus negatively impacting on relationships between agriculture and climate change. Conservation tillage (i.e. no-till and minimum tillage) has been recommended for enhancing soil organic carbon (SOC) and total nitrogen (STN) stocks while having a positive impact on food security, biodiversity, water quality and the environment. Nevertheless, positive responses were mainly reported in hot and semiarid climates, with rainfed crops and low N fertilization rates. Therefore, the main objective of this study was to test the adoption of conservation tillage in intensive maize cropping systems under temperate soil, with high N fertilization rate (> 200 kg N ha−1 yr−1) and organic matter input (i.e. manure distribution and high biomass return), and with permanent optimum water moisture due to irrigation. We conducted an 8-year field experiment on a maize (Zea mays L.) monoculture to assess: (i) the effect of no-till (NT) and minimum tillage (MT), on grain yield and biomass return as compared with conventional tillage (CT); (ii) how tillage systems affect the evolution of SOC and STN levels over time under these conditions; (iii) soil aggregation processes and mechanisms leading to SOC and STN changes in the long-term. Results showed that MT increased maize grain yield (+7 %) and total biomass (+10 %) compared with CT. Conversely, NT reduced maize grain and biomass production during the initial 5-year transition, but afterwards increased maize yield up to that of CT. At the end of the experiment, SOC sequestration was increased under NT and MT by 1.45 and 1.52 Mg C ha−1 yr−1 compared with CT, respectively. Also, STN accumulation was higher under NT and MT than under CT (+0.15 and +0.17 Mg N ha−1 yr−1, respectively). Most of such a SOC and STN increase was located into C- and N-rich macroaggregates. Within those macroaggregates (large macroaggregates, LM; small macroaggregates, sM), we found that C and N pools associated to mM accounted for between 41 and 65 % of total C and N content in NT and MT systems across the different soil layers, which is beneficial for long-term C and N stabilization in soils. Thus, introducing conservation tillage within intensive agricultural context devoted to maize monoculture as that of the Po Valley should be recommended to: (i) maintain (or even increase) maize yield, and (ii) enhance SOC and STN accumulation and stabilization. [ABSTRACT FROM AUTHOR]

No-till (NT) and cover crops (CCs) have been repeatedly recommended for building-up resilience of agro-ecosystems, enhancing soil biodiversity, and steering efficient nutrients cycling and yield. Yet, the overall impact of CCs on soil properties and dynamics during transition may highly change depending on CC species and interactions with field condition. In the present 3-yr field study, we (i) examined how selected CCs (i.e. rye [ Secale cereale L.]; phacelia [ Phacelia tanacetifolia Benth.] + white mustard [ Sinapis alba L.]; Italian ryegrass [ Lolium multiflorum Lam.] + crimson clover [ Trifolium incarnatum L.] + Persian clover [ Trifolium resupinatum L.]; hairy vetch [ Vicia villosa Roth] + crimson clover) affect yield performance in a crop sequence of maize (Zea mays L.), soybean (Glycine max L. Merr.), and maize under NT, and (ii) assessed the effects of CCs on inputs to the soil (i.e. biomass, carbon [C], and nitrogen [N]), soil organic C (SOC) and pools, as well as microarthropods and earthworms abundance and diversity. Grain yield during the initial 2-yr period was on average reduced with CCs by 1–23% in maize, and 1–33% in soybean. This effect was less evident with CC residues having low C:N ratio (< 20; i.e. hairy vetch + crimson clover) and erect habitus after termination (i.e. rye). Thereafter, CCs had no effect on maize yield the third year. Soil organic C and pools indicated that (i) the effect of our CC treatments over a 3-yr application is limited to the topmost 5 cm of soil, and (ii) the biomass input with CC residue and its C:N ratio are crucial for boosting soil C cycling. This was also the case for earthworm-related indicators, while arthropods mainly responded to different CCs in terms of evenness. Yet, our results on soil fauna showed that different groups or species need different time for showing effects, thus suggesting that responses may be fully effective in a >3-yr term. We concluded that CC mixtures that allow the best compromise between the high amount of residue and the low residue C:N ratio should be preferred for: (i) reducing possible detrimental effects on grain yield of maize and soybean, and (ii) enhancing soil C cycling and biodiversity. Therefore, selecting appropriate CC species in mixtures represents the main challenge at the field level for pursuing both objectives in the shortest timeframe. Within all options in summer crop sequences, here we reported that mixtures including leguminous cover crops might be primarily considered. • Cover crops during transition to NT may affect negatively maize and soybean yield. • Low C:N ratio of cover crop residues is pivotal to promote soil C cycling • Responses of soil C and pools to CCs over 3 years is limited to the topmost 5 cm of soil. • Leguminous-based mulch supports arthropod and earthworm communities. [ABSTRACT FROM AUTHOR]