Unexpected high reduction of methane emission via short-term aerobic pre-digestion of green manured soils before flooding in rice paddy

• Published in: The Science of the total environment Vol. 711; p. 134641
• Main Authors: Lee, Jin Ho, Park, Mun Hyeong, Song, Hyeon Ji, Kim, Pil Joo
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.04.2020
• Subjects: Agriculture; Biomass; Cover crop; Greenhouse gas; Manure; Methane; Methane flux intensity; Nitrous Oxide; Oryza; Soil; Biomass; Greenhouse gas; Cover crop; Methane flux intensity
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.134641

[Display omitted] •Biomass application as green manure increased CH4 emission by 5.8 times over chemical fertilization (NPK).•More than 10 days of aerobic pre-digestion of biomass amended soil before flooding decreased over 60% of seasonal CH4 flux.•Short-term aerobic pre-digestion of biomass amended soil did not change rice productivity.•More than 10 days of aerobic pre-digestion reduced more than 60% of CH4 flux intensity (kg CH4 kg−1 grain). Soil organic matter (SOM) is used as an important indicator of soil quality and a countermeasure to mitigate global warming. To increase SOM stock, cover cropping and its biomass incorporation as green manure are strongly recommended in mono-rice paddy soils. However, green manure application significantly increased greenhouse gas emission, in particular, methane (CH4) during rice cultivation, and then its simultaneous positive and negative outcome has become a serious issue. We hypothesized that the short-term aerobic pre-digestion of green manured soil under dry soil condition before flooding might degrade labile organic C into carbon dioxide (CO2) and then reduce CH4 production during the flooded rice cultivation period. In order to evaluate the feasibility of the short-term aerobic pre-digestion of green manured soil on reducing CH4 emission in rice paddy, cover crop biomass was incorporated in the inner dry soil at different time intervals from 0 to 30 days before flooding, and then CH4 and CO2 emission rates were monitored. Over 10 days of aerobic pre-digestion significantly decreased CH4 flux by 88–98% over the control (flooded soil without aerobic pre-digestion) during the two month’s incubation test. Similar results were observed during the field test, in which only at 10 days’ aerobic pre-digestion under dry soil condition, total CH4 flux decreased by approximately 60% over the control. This reduction effect was slightly increased when aerobic pre-digestion period was extended. In contrast, rice productivities were not significantly different from 0 to 30 days of aerobic pre-digestion. As a result, more than 10 days of aerobic pre-digestion of green manured soil before flooding decreased CH4 flux intensity (kg CH4 kg−1 grain) by 60% over the control. In conclusion, the short-term aerobic pre-digestion of green manured soil before flooding can be a good soil management strategy to mitigate CH4 emission without productivity decrease in rice field.