Muema Esther, Musyoki Mary, Mugadi Doreen, Chotte Jean-Luc, Mburu Harrison N., Vanlauwe Bernard, Kibunja Catherine N., Lesueur Didier.
2008. The impact of soil organic matter applications combined with mineral fertilization on both microbial and fungal soil communities in Kenya.
In : The 13th Congress of the African Association for Biological Nitrogen Fixation, satellite workshop on Mycorrhiza, December 15th - 18th 2008, Hammamet, Tunisia : book of abstracts. CBBC, AABNF, Tunisian Association for Biotechnology
Résumé : Soil fertility decline is increasingly leading to reduced food production worldwide. Over 70 % of small holder farmers in the central high lands of Kenya are using crop manure, animal wastes and inorganic fertilizers to increase their farms fertility and subsequent productivity. The dilemma with these practices is that less is known on the impact of these resources on the below ground biodiversity particularly the microbial communities which play a key role in determining soil quality. A study was carried out on a thirty-two year old long-term trial in Kabete, Kenya. These soils were treated with organic (maize stover at 10 t ha, farmyard manure at 10 t ha-) and inorganic fertilizers (120 kg N, 52.8 kg P plus farmyard manure at 10 t ha (N2P2+FYM), 120 kg N, 52.8 kg P plus maize stover at 10 t ha-1 (N2P2+R), 120 kg N, 52.8 kg P (N2P2), and a control (Nil and fallow) for over 30 years. We examined 16S rRNA gene and 28S rRNA gene fingerprints of bacterial and fungal communities, respectively, by PCR amplification and denaturing gradient gel electrophoresis (PCR-DGGE) separation. Bacterial community structure and diversity were negatively affected by N2P2, as evidenced by changes in the PCR-DGGE banding patterns. Bacterial community structure in the N2P2-treated soil was more closely related to the bacterial structure in the untreated soil (fallow and Nil) than that in soils treated with a combination of inorganic and organic or inorganic fertilizers alone. For the fungal community the negative effect of N2P2 alone was not as adverse as for the bacterial community structure since the soils treated with N,P2 were closely related to those treated with N2P2+FYM and N2P2+maíze stover. However, soils treated with organic inputs clustered away from soils amended with inorganic inputs. Organic inputs had a positive effect on both fungal and bacterial community structures with or without chemical fertilizers. Results from this study suggested that bacterial and fungal community structure was closely related to agro-ecosystem management practices conducted for over the past 30 years. In the frame of two other field trials, a new study compared the effect of different quality organic resources on microbial diversity under two different environments in Kenya. Treatments (Tithonia diversifolia, Calliandra callothyrsus, maize stover, Grevillea robusta, and goat manure), and mineral N (0, 120 kg N ha I) were assigned in a split - plot design laid out in a randomized complete block design (RCBD) with three replicates. The organic resources were assigned to the main plot and mineral N in the sub plots. Denaturing gradient gel electrophoresis (DGGE), was used to assess soil microbial diversity. There was a decrease in diversity of bacterial communities in Embu (Clay soil) and Machanga (Sandy soil) with application of different quality organic resources due to restriction of microorganism decomposers of particular materials. This decrease was significant at (p <0.05) within the clay soil. Different quality organic resources therefore affect soil microbial communities. More work on effect of mineral nitrogen rates, mixing of different quality materials on soil bacteria and narrowing down to specific bacteria groups like nitrifiers are encouraged.
Mots-clés Agrovoc : fertilité du sol, engrais organique, engrais minéral, flore du sol, flore microbienne, agroécosystème, système d'exploitation agricole
Mots-clés géographiques Agrovoc : Kenya
Classification Agris : P35 - Fertilité du sol
F04 - Fertilisation
P34 - Biologie du sol
Auteurs et affiliations
- Muema Esther, TSBF (KEN)
- Musyoki Mary, TSBF (KEN)
- Mugadi Doreen, TSBF (KEN)
- Chotte Jean-Luc, IRD (FRA)
- Mburu Harrison N., TSBF (KEN)
- Vanlauwe Bernard, TSBF (KEN)
- Kibunja Catherine N., KARI (KEN)
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Lesueur Didier, CIRAD-PERSYST-UPR Ecosystèmes de plantations (KEN)
ORCID: 0000-0002-6694-0869
Autres liens de la publication
Source : Cirad - Agritrop (https://agritrop.cirad.fr/562671/)
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