Residue Size, Diffusion, and Redox Potential: Effects of Soil Litter Dispersal on Greenhouse Gas Flux and Nutrient Availability.

There is enormous potential for agricultural soils to help mitigate climate change due to their large area and our control over their structure and inputs. Such an approach requires highly accurate predictions of greenhouse gas budgets for lands under different management practices, however, budgets of strong greenhouse gases CH₄ and N₂O can be difficult to accurately calculate across a field or landscape because of high temporal and spatial variability.  This variability is caused by precipitation events and gradients of electron donors and acceptors (i.e., redox potential) across sub-decimeter scales.   A primary control of redox potential in unsaturated soil is organic matter, for example, high rates of decomposition in patches of plant litter can deplete the region to anoxia causing anaerobic activities to follow.

In a laboratory incubation study we manipulated soil moisture and dispersal of agricultural litters (wheat straw, whole alfalfa) by varying litter patch size while maintaining total litter mass.  Litter patch size altered inorganic nitrogen concentrations and greenhouse gas flux budgets and dynamics.  The effects of litter patch size were generally on the same order of magnitude as effects of soil moisture and litter type, indicating that litter dispersal may be as important as these well-established controls of soil biogeochemistry in some systems.  In particular, agricultural practices that affect litter size and mixing in soils, such as compost additions and reduced tillage, may cause greenhouse gas production to vary in unexpected ways unless these phenomena are accounted for.