-The development and survival or disappearance of civilizations has been based on the performance of soils to provide food, fibre, and further essential goods for humans. Amongst soil functions, the capacity to produce plant biomass (productivity function) remains essential. This function is closely associated with the main global issues of the 21st century like food security, demands of energy and water, carbon balance and climate change. A standardised methodology for assessing the productivity function of the global soil resource consistently over different spatial scales will be demanded by a growing international community of land users and stakeholders for achieving high soil productivity in the context of sustainable multifunctional use of soils. We analysed available methods for assessing the soil productivity function. The aim was to find potentials, deficiencies and gaps in knowledge of current approaches towards a global reference framework. Our main findings were (i) that the soil moisture and thermal regime, which are climate-influenced, are the main constraints to the soil productivity potential on a global scale, and (ii) that most taxonomic soil classification systems including the World Reference Basis for Soil Resources provide little information on soil functionality in particular the productivity function. We found (iii) a multitude of approaches developed at the national and local scale in the last century for assessing mainly specific aspects of potential soil and land productivity. Their soil data inputs differ, evaluation ratings are not transferable and thus not applicable in international and global studies. At an international level or global scale, methods like agro-ecological zoning or ecosystem and crop modelling provide assessments of land productivity but contain little soil information. Those methods are not intended for field scale application to detect main soil constraints and thereby to derive soil management and conservation recommendations in situ. We found also, that (iv)

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To clarify the response of soil organic carbon (SOC) content to season-long grazing in the semiarid typical steppes of Inner Mongolia, we examined the aboveground biomass and SOC in both grazing (G-site) and no grazing (NG-site) sites in two typical steppes dominated by Leymus chinensis and Stipa grandis, as well as one seriously degraded L. chinensis grassland dominated by Artemisia frigida. The NG-sites had been fenced for 20 years in L. chinensis and S. grandis grasslands and for 10 years in A. frigida grassland. Aboveground biomass at G-sites was 21-35% of that at NGsites in L. chinensis and S. grandis grasslands. The SOC, however, showed no significant difference between G-site and NG-site in both grasslands. In the NG-sites, aboveground biomass was significantly lower in A. frigida grassland than in the other two grasslands. The SOC in A. frigida grassland was about 70% of that in L. chinensis grassland. In A. frigida grassland, aboveground biomass in the G-site was 68-82% of that in the NGsite, whereas SOC was significantly lower in the G-site than in the NG-site. Grazing elevated the surface soil pH in L. chinensis and A. frigida communities. A spatial heterogeneity in SOC and pH in the topsoil was not detected the G-site within the minimal sampling distance of 10 m. The results suggested that compensatory growth may account for the relative stability of SOC in G-sites in typical steppes. The SOC was sensitive to heavy grazing and difficult to recover after a significant decline caused by overgrazing in semiarid steppes.

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Summary The composition of soil organic matter (SOM) is influenced by land use and fertilization. We studied changes in the SOM in a long‐term field experiment on a sandy Podzoluvisol. The control plot and four combinations of manurial treatments of the experiment were selected: one with mineral fertilizer only and three combinations of organic manure with mineral fertilizer: cattle manure + NPK, cattle manure + PK and straw + NPK. The SOM was extracted by sodium pyrophosphate solution (pH = 10) and hot water (100°C). The extracts were analysed by Fourier‐Transform Infrared (FT‐IR) spectroscopy and gel permeation chromatography (GPC). The FT‐IR spectra from sodium pyrophosphate extracts indicate that composition of SOM is indeed influenced by different fertilization. The C=O band at 1710 cm–1 in the samples of the plots fertilized with cattle manure has the highest absorption intensity, whereas the material from the plot fertilized with straw + NPK has the least intense. The GPC analyses of the extracts showed that adding cattle manure + NPK increased the molecular size of SOM in comparison with the control plot. The analysis of hot‐water extracts with FT‐IR showed no significant differences in functional groups, but GPC chromatograms distinguished features in molecular size distribution. Fertilization with cattle manure increased the molecular size of the SOM in comparison with the control, but the differences in content of carboxylic groups and molecular weight were detected in sodium pyrophosphate extracts only.