Past land‐use changes, intensive cropping with large proportions of root crops, and preferred use of mineral fertilizer have been made responsible for proceeding losses of soil organic C (SOC) in the plough layer. We hypothesized that in intensive agriculturally managed regions changes in SOC stocks would be detectable within a decade. To test this hypothesis, we tracked the temporal development of the concentrations and stocks of SOC in 268 arable sites, sampled by horizon down to 60 cm in the Cologne‐Bonn region, W Germany, in 2005 and in 2013. We then related these changes to soil management data and humus balances obtained from farmers' surveys. As we expected that changes in SOC concentrations might at least in part be minor, we fractionated soils from 38 representative sites according to particle size in order to obtain C pools of different stability.We found that SOC concentrations had increased significantly in the topsoil (from 9.4 g kg−1 in 2005 to 9.8 g kg−1 in 2013), but had decreased significantly in the subsoil (from 4.1 g kg−1 in 2005 to 3.5 g kg−­1 in 2013). Intriguingly, these changes were due to changes in mineral‐bound SOC rather than to changes in sand‐sized organic matter pools. As bulk density decreased, the overall SOC stocks in the upper 60 cm exhibited a SOC loss of nearly 0.6 t C (ha · y)−1 after correction by the equivalent soil mass method. This loss was most pronounced for sandy soils [−0.73 t SOC (ha · y)−1], and less pronounced for loamy soils [−0.64 t SOC (ha · y)−1]; silty soils revealed the smallest reduction in SOC [−0.3 t SOC (ha · y)−1]. Losses of SOC occurred even with the overall humus balances having increased positively from about 20 kg C (ha · y)−1 (2003–2005) to about 133 kg C (ha · y)−1 (2005–2013) due to an improved organic fertilization and intercropping. We conclude that current management may fail to raise overall SOC stocks. In our study area SOC stocks even continued to decline, despite humus conservation practice, likely because past land use conversions (before 2005) still affect SOC dynamics.

Europe currently faces a decline in soil organic carbon (SOC) content under arable cropping irrespective of improved management practices. In this study we used more than 32 000 SOC data from the entire North Rhine–Westphalia (NRW) area to elucidate the temporal development and current state of SOC content in arable soil from 1979 to 2015 and, in addition, to identify potential causal factors of changes in SOC content. The dataset comprised 7401 data points for 1979–2003 from FIS StoBo, the branched information system on soil contamination in NRW, and 24 930 data points for 2007–2015 from the Agricultural Investigation and Research Institute NRW (LUFA NRW); all data considered refer to soil sampled at 0–30 cm. We found that topsoil carbon contents in arable soil increased over the entire NRW area during the 1980s (from 1.87% in 1979 to 2.82% in 1987), and that this increase was followed by an exponential decrease from 1988 to 2015 (1.42% SOC in 2015) without a new equilibrium being reached. Livestock‐poor regions showed a more rapid gain and a more rapid loss of SOC contents than regions with large livestock densities. The data correlated with changes in grassland area, which was reduced in NRW by about 360 000 ha mainly between 1970 and 1990; that is, recently ploughed grassland probably contributed to increasing averages of SOC contents in arable land during this period, but not thereafter. We conclude that past changes in land use controlled the evolution in SOC from 1979 to 2015, and there is little opportunity for changed management practices to prevent ongoing loss of SOC from the topsoil. Highlights The SOC contents in arable soil in North Rhine–Westphalia (NRW) show temporal trend. The SOC contents increased during the 1980s, but decreased thereafter. Data from the entire NRW area indicate that new SOC equilibria have not yet been reached. Past changes in land use still control current SOC evolution.

The modification of cellulosic materials is of great interest in materials research. Wet bacterial cellulose sheets were modified by an alkoxysilane under mild conditions to make them accessible to click chemistry derivatization. For this purpose (3‐azidopropyl)triethoxysilane was grafted covalently onto the cellulosic surface. The silanized bacterial cellulose sheets were characterized comprehensively by attenuated total reflectance FTIR spectroscopy, solid‐state NMR spectroscopy, thermogravimetric analysis, SEM with energy‐dispersive X‐ray spectroscopy, and elemental analysis. To demonstrate subsequent click chemistry functionalization, a new fluorophore based on fluorescein was synthesized and clicked to the silane‐modified bacterial cellulose. The new method renders bacterial cellulose and other never‐dried cellulosic materials susceptible to direct and facile functionalization in an aqueous medium without the need to work in water‐free organic phases or to employ extensive protecting group chemistry and functional group interconversion.