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| Titel |
Potential effects of earthworm activity on C and N dynamics in tropical
paddy soil |
| VerfasserIn |
Katharina John, Andrey S. Zaitsev, Volkmar Wolters |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133760
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| Publikation (Nr.) |
 EGU/EGU2016-14404.pdf |
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| Zusammenfassung |
| Earthworms are involved in key ecosystem processes and are generally considered important
for sustainable crop production. However, their provision of essential ecosystem services and
contribution to tropical soil carbon and nitrogen balance in rice-based agroecosystems are not
yet completely understood. We carried out two microcosm experiments to quantify the
impact of a tropical earthworm Pheretima sp. from the Philippines on C and N
turnover in rice paddy soils. First one was conducted to understand the modulation
impact of soil water saturation level and nitrogen fertilizer input intensity on C
and N cycles. The second one focused on the importance of additional organic
matter (rice straw) amendment on the earthworm modulation of mineralization in
non-flooded conditions. We measured CO2, CH4 (Experiments 1 and 2) and N2O
evolution (Experiment 2) from rice paddy soil collected at the fields of the International
Rice Research Institute (Philippines). Further we analysed changes in soil C and N
content as well as nutrient loss via leaching induced by earthworms (Experiment
2).
Addition of earthworms resulted in the strong increase of CH4 release under flooded
conditions as well as after rice straw amendment. Compared to flooded conditions,
earthworms suppressed the distinct CO2 respiration maximum at intermediate soil water
saturation levels. In the first few days after the experiment establishment (Experiment 1)
intensive nitrogen application resulted in the suppression of CO2 emission by earthworms at
non-flooded soil conditions. However, at the longer term perspective addressed in the second
experiment (30 days) earthworm activity rather increased average soil respiration under
intensive fertilization or rice straw amendment. The lowest N2O release rates were revealed
in the microcosms with earthworm and straw treatments. The combined effect of N fertilizer
and straw addition to microcosms resulted in the increased leachate volume due
to earthworm bioturbation activity. The mean relative C loss with leaching was
increased by earthworms under intensive fertilization and consequently resulting soil
C content in the end of Experiment 2 decreased. N concentration in the leachate
remained unaffected by earthworms although the remaining N content in soil with
straw application and earthworm treatment was significantly higher than in the
control.
Our results showed that the potential role of earthworms in C-stabilization is confined to
moderately irrigated soils that allow high earthworm activity. Earthworm effects on C and N
release under non-flooded conditions were largely modulated by the application of N
fertilizer (urea) and by the amendment of rice straw. Our findings suggest that the presence
of earthworms significantly affect C and N budgets in rice paddy soil, especially
in the intensively managed non-flooded fields. In the short term perspective they
sequester C and N loss from soil. However, in the longer term (ca. 30 days) this
sequestration effect remains significant only for nitrogen under the straw application
treatment.
The study was supported by ICON project within the DFG-Research Unit FOR 1701. |
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