We examined the spatial variability in SOC in a 10 000 ha landscape in SW China. The spatial variability in SOC was largest at the plot scale (1 ha) and the associations between SOC and land use, soil properties, vegetation, and topographical attributes varied across plot to landscape scales. Our results show that sampling designs must consider the controlling factors at the scale of interest in order to elucidate their effects on SOC against the variability within and between plots.

Roots deeper in the soil are made up of more carbon and less nitrogen compared to roots at shallower depths, which may help explain deep-carbon origin. A comparison of prairie and maize rooting systems showed that in moving from prairie to maize, a large, structural-tissue-dominated root carbon pool with slow turnover concentrated at shallow depths was replaced by a small, nonstructural-tissue-dominated root carbon pool with fast turnover evenly distributed in the soil profile.

Alexander von Humboldt was an inspiring scientist in the early 1800s, traveling widely, making many measurements, and linking different scientific disciplines while keeping an eye open to the needs of society. This is particularly relevant today in our information society, and researchers in developing countries are advised to follow the von Humboldt example when planning their future research.

Injection of biogas digestates (BDs) is suspected to increase losses of N₂O and thus to counterbalance prevented NH₃ emissions. We determined N₂O and N₂ losses after mixing high concentrations of BD into two soils by an incubation under an artificial helium–oxygen atmosphere. Emissions did not increase with the application rate of BD, probably due to an inhibitory effect of the high NH₄⁺ content in BD on nitrification. However, cumulated gaseous N losses may effectively offset NH₃ reductions.