Wed, Aug 04, 2021:On Demand
Background/Question/Methods
Recent studies have emphasized the potentially important but opposing effects of manganese (Mn) and nitrogen (N) enrichment on litter decomposition in forest systems. Increasing N deposition can lead to soil acidification that mobilizes Mn. This is particularly relevant in agroecosystems that depend heavily on N fertilization. However, no studies have examined the interactive effect of N and Mn fertilization on crop residue decomposition and soil carbon (C) cycling. Our current study aims to fill this gap. We conducted a laboratory microcosm experiment by adding 13C labeled plant residue to agricultural soils that received 225 kg N ha-1 yr-1 for 27 years and comparable soils that received no N fertilization. These soils also received one out of three levels of Mn: ambient (no additional Mn), low Mn (∼50 kg Mn ha-1), or high Mn (∼250 kg Mn ha-1). The soils were incubated at 65% water holding capacity at 21oC. Soil respiration was measured periodically to determine residue mineralization, and destructive sampling was done at day 30 to determine soil pH, dissolved organic C (DOC) and microbial biomass C (MBC).
Results/Conclusions After 30 days of incubation, DOC, MBC, and cumulative CO2 production from residue was higher in long-term N fertilized soils than in soils without N fertilization, indicating that increased N availability promoted microbial biomass growth and decomposition of the residue Mn amendments at both levels significantly increased 30 days CO2 mineralization from residue in long-term N fertilized soil, but no such effect was found in soil without N fertilization. These results indicate that the effect of Mn on initial residue decomposition depends on soil N availability. Improving our understanding of the factors that alter residue decomposition and C stocks will ultimately help enhance soil health and predict ecosystem-climate feedback.
Results/Conclusions After 30 days of incubation, DOC, MBC, and cumulative CO2 production from residue was higher in long-term N fertilized soils than in soils without N fertilization, indicating that increased N availability promoted microbial biomass growth and decomposition of the residue Mn amendments at both levels significantly increased 30 days CO2 mineralization from residue in long-term N fertilized soil, but no such effect was found in soil without N fertilization. These results indicate that the effect of Mn on initial residue decomposition depends on soil N availability. Improving our understanding of the factors that alter residue decomposition and C stocks will ultimately help enhance soil health and predict ecosystem-climate feedback.