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The design of sustainable, high-yielding continuous cropping systems requires to maintain, or even restore, critical ecosystem properties, such as soil functioning. In the rolling Pampa (Argentina), total soil organic carbon decreased by 15–40% due to continuous agriculture. Therefore, soils are far from their potential carbon saturation. The most promising strategies to increase yield and restore carbon rely on the sustainable intensification of the current cropping systems based on no-tillage practices. Such strategies also involve increasing resource use through cover crops, increasing cropping intensity, and performing accurate and flexible fertilization and crop protection schemes. This study evaluated the effects of different cropping systems on soil organic carbon stocks in the uppermost 20 cm of the soil profile. We performed a 5-year experiment combining five cropping systems with different cash crop sequence (soybean mono-cropping and two different rotations) and agronomic technology (genotypes, fertilization, and crop protection), which in turn were evaluated under both fallow and cover cropping. Five years after the beginning of the experiment, all systems had a net positive balance of soil carbon accumulation, which averaged 2.25 t C.ha-1.yr-1. On average, 41% of plant carbon inputs remained within the first 20 cm of the soil profile. Cover crops increased plant carbon inputs, with larger effects as the cash crops occupied a shorter period in the field. Therefore, compared to fallow, cover crop doubled carbon input in soybean mono-cropping, had intermediate increments in the maize-soybean sequence, and had the lowest increments in the wheat/soybean-maize-soybean sequence. Under fallow, both rotations outperformed the plant carbon inputs of soybean mono-cropping. Management intensification, only evaluated for rotations, increased plant carbon inputs and soil carbon accumulation in a synergistic interaction with cover crop. Our results indicate that increasing carbon inputs through crop rotation, cover cropping and better agronomic technology is an opportunity to revert the long trend of soil carbon deficit of these agricultural lands. • Approximately 41% of plant carbon inputs remained in soil. • Intensified management and cover cropping acted synergically. • Crop rotations with more frequency of maize accumulated more soil carbon. • Cover cropping doubled annual carbon inputs of soybean mono-cropping. [ABSTRACT FROM AUTHOR]

Agricultural intensification has increased food production by reducing crop diversity and increasing fertilization and crop protection. Unfortunately, intensification has also reduced soil ecosystem services. Diversifying crop rotations could be a feasible alternative to promote positive feedbacks between soil biota and soil properties. Here, we investigated the impact of diversifying crop rotations on functional composition and diversity of the heterotrophic soil bacterial communities. We studied three frequent rotations with a total number of crops ranging from two to four. Before the experiment, all plots were cultivated with soybean. In the first experimental year, the crop sequences were (1) fallow/soybean, (2) barley/soybean, and (3) field pea/maize. In the second year, all plots were subjected to a wheat/soybean double crop. The experiment was replicated in three locations of the Rolling Pampa (Argentina). Soil and plant sampling took place immediately after the soybean harvest, in the second year. The most diverse rotation (field pea/maize, wheat/soybean) showed the highest standing biomass and litter and the most metabolically diverse and active soil microbial community (P ≤ 0.05). In turn, metabolic diversity was positively associated with plant and litter biomass (r 2  = 0.7) and with soil pH (r 2  = 0.72). Our results revealed that crop rotation affects soil metabolic bacterial diversity and activity (P ≤ 0.05). The most diverse rotation (four different crops) had also the most diverse and active soil microbial biota, concomitantly with a higher plant biomass production and soil pH. Because soil microbial activity and metabolic diversity detected in specific rotations potentially contribute to soil aggregate formation and other soil properties intimately related with nutrient cycling and plant production, the negative effect of agricultural intensification could be attenuated by designing specific and more diverse crop rotations. [ABSTRACT FROM AUTHOR]

Many complex, natural landscapes have been transformed into simpler agroecosystems by continuous cropping and the application of glyphosate and fertilizers. The current mosaic with different land cover types can harbor different soil microbial communities. Here, we investigated how the microbial community and ryegrass plants responded to glyphosate and nitrogen application to soils from four different cover types (soybean monocropping; wheat/soybean-field pea rotation, herbaceous- and woody- uncropped margins). We predict that soils from different land cover types will display different responses of their detritivore microbial communities and plant growth to herbicide and fertilizer application. All the studied variables differed among land cover types. Woody margins tripled the soil carbon content and the microbial respiration of herbaceous margins, although the later had more diverse soil microbial communities. Soils from soybean monoculture had higher respiration rates (37%) than those from crop rotation, where ryegrass accumulated lower biomass (12% lower). Despite these differences between land cover types, neither glyphosate nor nitrogen fertilization significantly influenced these properties. Only ryegrass plants growing on glyphosate-treated soils accumulated more biomass than the rest whereas they did not respond to nitrogen. These results suggest that glyphosate and nitrogen at recommended doses did not have a significant impact on the soil performance of the different types of cover. • Different land covers promote environmental and microbial heterogeneity in arable soils. • Soil microbes and ryegrass growing in monocropping soils outperformed those from crop rotation. • Microbial respiration and composition from different land covers were not affected by glyphosate and nitrogen addition. [ABSTRACT FROM AUTHOR]