|PARAJULI, BINAYA - Clemson University|
|YE, RONGZHONG - Clemson University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2021
Publication Date: 11/10/2021
Citation: Parajuli, B., Ye, R., Szogi, A.A. 2021. Nitrogen addition reduced the decomposition of organic carbon derived from long-term conservation management. Meeting Abstract. Poster number: 1272.
Interpretive Summary: Abstract Only.
Technical Abstract: Conservation management practices, such as reduced tillage and residue returns, are known to improve soil organic carbon (SOC) content in a range of cropping systems. However, the stabilization and decomposition of the accumulated SOC are rarely addressed, especially in changing management practices. The objective of this study was to investigate how organic inputs and nitrogen (N) fertilization affected the stability and decomposition of SOC in soils, where SOC accumulated after 40-years of conservation management practices. We hypothesized that carbon (C) inputs would increase the decomposition of the accumulated SOC, and N addition would further stimulate the decomposition. We tested these hypotheses by incubating soils with carbon-labeled (13C) residue and inorganic-N in the dark, at room temperature for 55 days. We determined the respiratory production of carbon dioxide (CO2), 13C-CO2, nitrous oxide (N2O) production and enzymatic activities. The addition of plant residues increased microbial biomass C, activities of C-cycling enzymes (ß-D-cellubiosidase, ß-glucosidase, N-acetyl-ß-glucosaminidase, and ß-xylosidase), N-cycling enzymes (leucine aminopeptidase, N-acetyl-ß-glucosaminidase) and cumulative CO2 and N2O production, supporting our C input hypothesis. However, when N was added together with the plant residue, the decomposition reduced by 11%, not supporting our N addition hypothesis. The addition of plant residue increased cumulative N2O production by 12-fold when compared with soils without any amendments, while addition of inorganic-N further stimulated and increased the N2O production by 24-fold. The N addition increased microbial biomass C and N but did not affect cumulative CO2 production and the measured enzymatic activities. Inorganic N concentration was negatively correlated to cumulative CO2 production (R2= -0.60, p<0.001), cumulative N2O production (R2= -0.45, p<0.05) and measured C and N cycling enzyme activities. The result suggests that accumulated SOC derived from long-term conservation management might respond differently to changing management practices that affect the C and N inputs to agricultural soils and hence the SOC stability.