Journal
GEODERMA
Volume 401, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.geoderma.2021.115342
Keywords
CO2 emission; N2O emission; Soil aggregate; Straw addition; Enzyme activities
Categories
Funding
- National Key Research and Development program of China [2017YFD0800102]
- National Natural Science Foundation of China [41671253, 31670506]
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This study revealed that the addition of straw significantly increased CO2 and N2O emissions in soil aggregates, with the <0.25 mm fraction showing a significantly lower CO2 emission compared to the larger fractions. The 1-2 mm fraction had the highest N2O emissions across both straw-unamended and straw-amended treatments.
Greenhouse gas (GHG) emissions from agricultural soil have been widely discussed to combat the risks of global warming. However, GHG emissions at the soil aggregate scale have yet to be elucidated, particularly in association with straw incorporation. In this study, three different sizes of soil aggregates (1-2, 0.25-1, and < 0.25 mm) were incubated in the laboratory at 25 degrees C for 58 days with and without rapeseed straw (Brassica napus L.) addition to determine the extent to which aggregate sizes contribute mostly to carbon dioxide (CO2) and nitrous oxide (N2O) emissions upon straw addition. Results showed that cumulative CO2 emission in < 0.25 mm fraction (546 mg C kg(-1) soil) was significantly (P < 0.001) lower than that in 0.25-1 mm (810 mg C kg(-1) soil) and < 1-2 mm (762 mg C kg(-1)- soil) fractions in straw-unamended treatments. Straw addition increased cumulative CO2 emissions by 7.2-, 5.87-, and 13.1-fold from 1 to 2, 0.25-1, and < 0.25 mm fractions, respectively, compared with those of the corresponding straw-unamended treatments. Straw addition increased cumulative N2O emissions in each size of aggregates, and cumulative N2O emissions in 1-2 mm fraction ranked the first across the straw-unamended and straw-amended treatments. The activities of beta-glucosidase, beta-cellobiohydrolase, N-acetyl-beta-D-glucosaminidase, and leucine aminopeptidase were enhanced by straw addition in each size of aggregates, and < 0.25 mm fraction exerted the lowest enzyme activities. Structural equation modeling and redundancy analysis confirmed that the interaction between soil physiochemical parameters (nitrate nitrogen and dissolved organic C) and specific enzyme activities was the key driver for regulating CO2 and N2O emissions. These results implied that identifying the straw as a function of aggregate-scale GHG dynamics could improve the mechanistic understanding of global warming.
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