Litter decomposition in the mixed Chromolaena odorata (Asteraceae, herbaceous)-Cajanus cajan (Fabaceae, ligneous) fallow: synergistic or antagonistic mixing effect?

• Published in: Agroforestry systems Vol. 97; no. 8; pp. 1525 - 1539
• Main Authors: Kouadio, Hervé K., Koné, Armand W., Touré, Guy-Pacome T., Konan, Louis N., Yapo, Guy R., Abobi, Hebert D. A.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-12-2023; Springer Nature B.V
• Subjects: Agriculture; Asteraceae; Biomedical and Life Sciences; Cajanus cajan; Chromolaena odorata; Decomposition; Fabaceae; Forestry; Leaf litter; Life Sciences; Litter fall; Magnesium; Mathematical analysis; Mixtures; Organic carbon; Organic soils; Plant species; Soils; Subsistence agriculture; Ecological intensification; Pigeon pea; Species complementarity; Soil carbon sequestration; Litter interactions; Plant functional diversity
• ISSN: 0167-4366; 1572-9680
• DOI: 10.1007/s10457-023-00874-8

One option of improving the
Chromolaena odorata
(Asteraceae) fallow on which subsistence agriculture depends in West Africa could be the integration of ligneous plant species without drastically limiting litter decomposition. This study conducted in Central Côte d’Ivoire aimed to explore the effect of such a mixture (referred to as Mixing effect—ME) on leaf litter decomposition. It included pure fallows of 
C. odorata
(CO) and
Cajanus cajan
(CC), and a mixed fallow of the two species (COCC) established at four sites. Litter decomposition was studied in litterbags for six months. Observed and expected mass losses were calculated in the litter mixture, which then allowed calculation of the ME. Soil-surface litter mass was highest in CC (9.3 ± 0.3 Mg ha
−1
), lowest in CO (5.5 ± 0.2 Mg ha
−1
) and intermediate in COCC (7.9 ± 0.3 Mg ha
−1
). Initial litter C concentration, and the C:N and C:P ratios were higher in CC than in CO while the opposite was observed for litter Ca
2+
and Mg
2+
, reflecting significant dissimilarities in the quality of the litter species. Interestingly, these parameters were those determining the overall litter mass loss. The decomposition coefficient in COCC (
k
 = 0.45 month
−1
) was lower than that in CO (
k
 = 0.93 month
−1
) but higher than that in CC (
k
 = 0.21 month
−1
). The overall ME was found to be non-additive antagonistic (ME = -8.2%,
p
 = 0.005) without being consistent over the decomposition period: it was antagonistic over the first two months (ME = -12%,
p
 = 0.002) and additive afterwards (ME = -1%,
p
 = 0.97). The higher litterfall and litter C concentration in COCC relative to CO fallows coupled with the additive effect over the second phase of decomposition predict a faster soil organic carbon accumulation in the mixed fallow as is perceptible in the two-year old plots of the study.