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Deep‐ploughing far beyond the common depth of 30 cm was used more than 50 years ago in Northern Germany with the aim to break root‐restricting layers and thereby improve access to subsoil water and nutrient resources. We hypothesized that effects of this earlier intervention on soil properties and yields prevailed after 50 years. Hence, we sampled two sandy soils and one silty soil (Cambisols and a Luvisol) of which half of the field had been deep‐ploughed 50 years ago (soils then re‐classified as Treposols). The adjacent other half was not deep‐ploughed and thus served as the control. At all the three sites, both deep‐ploughed and control parts were then conventionally managed over the last 50 years. We assessed yields during the dry year 2019 and additionally in 2020, and rooting intensity at the year of sampling (2019), as well as changes in soil structure, carbon and nutrient stocks in that year. We found that deep‐ploughing improved yields in the dry spell of 2019 at the sandy sites, which was supported by a more general pattern of higher NDVI indices in deep‐ploughed parts for the period from 2016 to 2021 across varying weather conditions. Subsoil stocks of soil organic carbon and total plant‐available phosphorus were enhanced by 21%–199% in the different sites. Root biomass in the subsoil was reduced due to deep‐ploughing at the silty site and was increased or unaffected at the sandy sites. Overall, the effects of deep‐ploughing were site‐specific, with reduced bulk density in the buried topsoil stripes in the subsoil of the sandy sites, but with elevated subsoil density in the silty site. Hence, even 50 years after deep‐ploughing, changes in soil properties are still detectable, although effect size differed among sites. [ABSTRACT FROM AUTHOR]

The foothill areas of eastern Turkey are an arid and semiarid region with natural salinization, where calcareous alluvial saline soils (Calcaric Fluvisols) are circulated as a result of floods of the Aras River. In this study, the effects of salinity and alkalinity on soil aggregate size distribution and enzyme activities at different aggregate size were investigated. For this purpose, soil samples were collected with three replicates at saline, alkaline, saline-alkaline and non-saline–alkaline areas and passed through into different sieves (2, 1, 0.850, 0.425, 0.106 and 0.02 mm) by dry sieving method for determining aggregate weight distribution in each macro (2–0.45 mm) and micro (0.45–0.02 mm) aggregates. For determining aggregate size distribution, sieves were shaken using a horizontal shaking machine (Retsch, AS 200 basic, Haan, Germany). The soil enzymes were determined in these aggregate sizes (2–1, 1–0.850, 0.850–0.425, 0.425–0.106, 0.106–0.02 mm) for all soil types. All soils belonged to the clay loam with the carbon content in the range of 0.5–0.8%, while the percentage of exchangeable sodium for the non-saline–alkaline and alkaline–saline soils was from 3.5 to 22%, but the pH diapason from 8.3 to 8.9. Results showed that soil salinity and alkalinity decreased the weight of macro aggregates and increased the weight of micro aggregates, besides soil salinity and alkalinity decreased soil enzyme activities. But soil salinity decreased enzyme activity more than alkalinity. Furthermore, the highest urease and catalase activities were in macro aggregates (0.850–0.425 mm aggregate size) for all soil types. The reason may be that macro aggregates contain higher organic matter and organic carbon than micro aggregates. Consequently, the highest enzyme (urease and catalase) activities were detected in macro aggregates. [ABSTRACT FROM AUTHOR]

• Simulated warming caused a rapid loss of OC in mountainous grassland soils rich in OM. • SOC loss was associated with a disruption of large-macroaggregates. • Intensive grassland slightly offset OC losses and promoted SM formation. • Soil perturbation effects have to be differentiated from climate change effects. Mountainous grassland soils are considered one of the most unique biological hotspots, rich in organic carbon (OC). At the same time, they are exposed to great threats, as climate warming is more pronounced in mountainous regions than in lowland areas. In this study, we assessed the effect of simulated warming (+1K, +2K, and + 3 K) on OC stocks and soil structure in grassland soils of the Northern Limestone Alps in Germany by translocating plant-soil mesocosms from high- (1260 m a.s.l., Rendzic Phaeozem) and mid- (860 m a. s. l., Haplic Cambisol) to low-elevation (600 m a.s.l). Plant-soil mesocosms were exposed to both extensive and intensive grassland management practices. Four years after translocation, we observed a rapid decrease of topsoil SOC stocks under intensive (−1.0 t C ha yr−1) and extensive management (-2.2 t C ha yr−1), under the highest temperature increase. Intensive management with about 1 t C ha−1 yr−1 higher manure C return than extensive management (1.6 vs. 0.8 t C ha−1 yr−1 intensive and extensive, respectively) may explain the difference in SOC losses between different management treatments. Under both management practices, the loss of SOC was mainly associated with a decrease of large macroaggregates, at both management practices. In addition, different aggregate specific OC loss rates resulted in an altered distribution of OC among the aggregate size classes. Our study provides evidence that simulated climate change induced a rapid and substantial decline of SOC in mountainous, OC-rich grassland soils, which may be attributed to decreased physical OC protection within large macroaggregates. Optimized grassland management in form of increased application of organic fertilizers could only partially offset the SOC loss by improved formation of small macroaggregates. [ABSTRACT FROM AUTHOR]

[Display omitted] • Topsoil SOC stocks and soil structure recovered 26 years after topsoil removal. • Topsoil buried under the plough layer non-linearly lost 30–50% of SOC in 55 years. • Topsoil SOC recovery and stability of buried SOC was dependent on N fertilisation. Erosion of fertile topsoil means severe land degradation and yield loss. Here, we show that reformation of the fertile topsoil and crop yield increase is possible by good agricultural management within a few decades. Evidence relies on a unique long-term field experiment in NE Germany, where in 1964 the sandy soil (Luvisol) had been excavated to 52 cm and refilled with subsoil material of 52 cm thickness. Undisturbed trials served as controls, these were all combined with either no fertilisation, mineral fertilisation or a combined mineral and organic fertilisation. It took only 26 years until new topsoil had been formed. Its soil organic carbon (SOC) and total N stocks and the aggregate size distributions equalled that of the other treatments; SOC sequestration corresponded to 28 Mg SOC ha−1. The former topsoil buried below the plough layer lost 30–50 percent of its SOC during 5 decades in a non-linear manner. We conclude that our current agricultural tools can restore degraded arable land rather fast and contribute to climate change mitigation through a significant SOC sequestration as well. [ABSTRACT FROM AUTHOR]