Biophysical Drivers of Organic Material Decomposition in Long‐Term Cropping Systems Across Contrasting Soil Textures

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ABSTRACT The decomposition of organic material (OM t ) in agricultural ecosystems impacts soil fertility and is influenced by land management. This study aimed to unravel the biophysical drivers contributing to the decomposition of OM t in long‐term cropping systems (crop rotation with and without ley, bare fallow and perennial grassland) on sandy and silty soils. First, we considered physical properties, such as water‐stable aggregates, gas transport and pore size distribution, as well as microbiological properties, including the biomass of arbuscular mycorrhizal fungi, saprophytic fungi and bacteria and fluorescein diacetate enzyme activity. Soil organic carbon (SOC) content, total nitrogen, water‐extractable phosphorus, plant‐available potassium and magnesium, pH and electrical conductivity were also determined. Finally, we elucidated the relationships between OM t decomposition and the examined soil properties. The OM t decomposition was assessed using the tea bag protocol with two types of tea representing OM t with a high C:N ratio (low quality) and a low C:N ratio (high quality). Results showed that the difference in the soil properties between arable and ley‐arable rotation was more pronounced in the sandy soil than in the silty soil. The OM t decomposition showed no clear difference in the silty soil among different cropping systems, while there was a greater decomposition of both types of OM t in the arable rotation than in the other systems in the sandy soil. For both sites, the greater decomposition of low‐quality OM t was associated with soil biochemical properties, while the decomposition of high‐quality OM t was associated with gas diffusion; for the sandy soil, the former was also associated with nutrient contents, and the latter was associated with SOC, soil structural properties and enzyme activity. In summary, the biophysical drivers for OM t decomposition varied with the OM t quality and soil texture, and there was no consistent effect of crop rotation on OM t decomposition depending on the soil texture.

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