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Ridge and furrow cultivation is the most widely used agricultural technique in medieval and postmedieval Europe, but the fertilization of soils during their use is not yet fully understood. Pedological analyses of this cultivation technique provided information, which led to the assumption that some of the investigated sites in Northern and Central Germany were manured with livestock excrements during cultivation. The objective of this study is to determine whether and how the soils have been fertilized and which materials were applied for this purpose. We investigated soils at five sites using phosphate and steroid analyses (stanols and bile acids), black carbon analyses, and a micromorphology study. The results showed that livestock waste was likely used as fertilizer at four of the five studied sites at low intensities, with pigs and herbivores being the probable sources of the excrement. But also the application of human feces to the soil might be possible at least at one site. Often used agricultural methods such as plaggen cultivation and an intentional charcoal input to enhance soil fertility could not be clearly verified for our study sites. [ABSTRACT FROM AUTHOR]

Substitution of mineral fertilizers with organic soil amendments is postulated to improve productivity‐relevant soil properties such as aggregation and organic matter (OM) content. However, there is a lack of studies analyzing the effects of biochar and biogas digestate versus mineral fertilizer on soil aggregation and OM dynamics under temperate field conditions. To address this research gap, a field experiment was sampled four years after establishment on a sandy Cambisol in Germany where mineral fertilizer or liquid biogas digestate was applied with or without 3 or 40 Mg biochar ha−1 (produced at 650°C). Soil samples were analyzed for soil organic carbon (SOC) content, pH, cation exchange capacity, bulk density, water‐holding capacity, microbial biomass, aggregate size class distribution, and the SOC content associated with these size classes. 40 Mg biochar ha−1 significantly increased SOC content in all fractions, especially free particulate OM and the 2–0.25 mm fraction. The yield of small macroaggregates (2–0.25 mm) was increased by biochar, but cation exchange capacity, water‐holding capacity, and pH were not consistently improved. Thus, high‐temperature biochar applied to a sandy soil under temperate conditions is primarily recommended to increase SOC content, which could contribute to climate change mitigation if this C remains sequestered over the long‐term. Fertilizer type did not significantly affect SOC content or other measured properties of the sandy Cambisol, suggesting that replacement of mineral fertilizer with digestate has a neutral effect on soil fertility. Co‐application of biochar with digestate provided no advantages for soil properties compared to co‐application with mineral fertilizer. Thus, independent utilization of these organic amendments is equally suitable. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, biochar has been discussed as an opportunity for carbon sequestration in arable soils. Field experiments under realistic conditions investigating the CO2 emission from soil after biochar combined with fertilizer additions are scarce. Therefore, we investigated the CO2 emission and its 13C signature after addition of compost, biogas digestate (originating from C4 feedstock) and mineral fertilizer with and without biochar (0, 3, 10, 40 Mg biochar/ha) to a sandy Cambisol in Northern Germany. Biomass residues were pyrolized at ~650°C to obtain biochar with C3 signature. Gas samples were taken biweekly during the growing season using static chambers three years after biochar substrate addition. The CO2 concentration and its δ13C isotope signature were measured using a gas chromatograph coupled to an isotope ratio mass spectrometer. Results showed increased CO2 emission (30%–60%) when high biochar amount (40 Mg/ha) was applied three years ago together with mineral fertilizer and biogas digestate. On average, 59% of the emitted CO2 had a C3 signature (thus, deriving from biochar and/or soil organic matter), independent of the amount of biochar added. In addition, our results clearly demonstrated that only a small amount of released CO2 derived from biochar. The results of this field experiment suggest that biochar most likely stimulates microbial activity in soil leading to increased CO2 emissions derived from soil organic matter and fertilizers mineralization rather than from biochar. Nevertheless, compared to the amount of carbon added by biochar, additional CO2 emission is marginal corroborating the C sequestration potential of biochar. [ABSTRACT FROM AUTHOR]