Changes in belowground carbon stocks during the rotation "Tree improved fallow - crops" in the dry tropics of Cameroon
Belowground C stocks in the 0-20 cm soil layer were evaluated in a tree fallow/crop rotation on an alfisol in Northern Cameroon (1050 mm annual rainfall). Belowground C was separated into soil C (SOM of 0-2 mm size) and root C. Three separated fallow systems planted with Acacia polyacantha (N2 fixing species), Senna siamea and Eucalyptus camaldulensis were compared to a spontaneous herbaceous fallow. The fallow period lasted 5 years and was followed by maize (Zea mays L.) cultivation. After 5 years of fallow, the root C (1 t ha-1 under the herbaceous fallow to 8.7 t ha-1 under A. polyacantha), was the main contributor to the increases in belowground C stocks and the only significant increase of the soil C occurred in the A. polyacantha fallow (+ 2.5 t ha-1, + 28%), mainly due to particulate macro-organic matter (50 to 2000 microm size fraction). After tree logging, slash and burn, the roots of the fallow vegetation decomposed rapidly within the first two years of cropping, mainly through macrofauna activities, especially termites. By contrast, soil C stocks showed little changes during this period. Only the A. polyacantha fallow resulted in a net increase in maize grain production over two seasons, in relation to greater soil N availability than in the other fallows. In leguminous tree fallow systems, low C sequestration in SOM may be associated with high root mass and fast C turn-over linked with increased nutrient flows and storage, which results in maintaining crop production in the long term.
| Main Authors: | , , , , |
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| Format: | conference_item biblioteca |
| Language: | eng |
| Published: |
IFAS
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| Subjects: | F08 - Systèmes et modes de culture, F60 - Physiologie et biochimie végétale, F40 - Écologie végétale, http://aims.fao.org/aos/agrovoc/c_1229, |
| Online Access: | http://agritrop.cirad.fr/536295/ |
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| Summary: | Belowground C stocks in the 0-20 cm soil layer were evaluated in a tree fallow/crop rotation on an alfisol in Northern Cameroon (1050 mm annual rainfall). Belowground C was separated into soil C (SOM of 0-2 mm size) and root C. Three separated fallow systems planted with Acacia polyacantha (N2 fixing species), Senna siamea and Eucalyptus camaldulensis were compared to a spontaneous herbaceous fallow. The fallow period lasted 5 years and was followed by maize (Zea mays L.) cultivation. After 5 years of fallow, the root C (1 t ha-1 under the herbaceous fallow to 8.7 t ha-1 under A. polyacantha), was the main contributor to the increases in belowground C stocks and the only significant increase of the soil C occurred in the A. polyacantha fallow (+ 2.5 t ha-1, + 28%), mainly due to particulate macro-organic matter (50 to 2000 microm size fraction). After tree logging, slash and burn, the roots of the fallow vegetation decomposed rapidly within the first two years of cropping, mainly through macrofauna activities, especially termites. By contrast, soil C stocks showed little changes during this period. Only the A. polyacantha fallow resulted in a net increase in maize grain production over two seasons, in relation to greater soil N availability than in the other fallows. In leguminous tree fallow systems, low C sequestration in SOM may be associated with high root mass and fast C turn-over linked with increased nutrient flows and storage, which results in maintaining crop production in the long term. |
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