1. SOIL FAUNA AND NUTRIENT MANAGEMENT FOR IMPROVING AGRICULTURAL PRODUCTION
THROUGH LEGUME USE IN OUMÉ, MID‐WEST CÔTE D’IVOIRE
Armand W. Koné 1,*, Jean T. Gonnety 1, Martinez A. Guéi 1, Jules A. Assi 1, Aurélie A. N’Dri 1,
Pascal K.T. Angui 1, Jérôme E. Tondoh 1,2, Y. Tano 3
(1) Université d’Abobo‐Adjamé, 02 BP 801 Abidjan 02, Côte d’Ivoire; (2) AfSIS Project, CIAT‐TSBF, IER Sotuba, BP 262, Bamako, Mali;
(3) Université de Cocody, 22 BP 582 Abidjan 22, Côte d’Ivoire
*Correspondence: konearmand@yahoo.fr
INTRODUCTION
Farmers in the Oumé area are faced with decreasing soil fertility, as a result of widespread deforestation to establish cocoa and coffee farms. In order to address this issue and thereby,
stabilize agriculture in the region, the project, entitled: Conservation and Sustainable management of Below‐Ground Biodiversity (SM‐BGBD) emphasized, soil management systems that
promote soil organisms, which are known to provide many ecosystem services (Hole, 1981; Brown, 1999). In this framework, improved fallows were considered as important components, as
they have a potential to improve the physical, chemical and biological status of soils (Okpara et al., 2005; Blanchart et al., 2006; Koné et al.; 2008a & 2008b). This study deals with both soil
chemical and biological characteristics, and their relationship to maize production after 9‐month of legume fallows establishment.
MATERIAL AND METHODS
Study site and experimental design Soil and fauna samplings
The study was carried out in Goulikao (6.3 N, 5.3 W) village and surrounding camps (Petit‐ Soil samples were collected from the 0‐10 cm layer, In both legume‐based and control
plots, at 3 points, and mixed into a composite sample. Then, they were air‐dried, at
Bouaké and Djèkoffikro) in Oumé, mid‐West Côte d’Ivoire. The mean annual rainfall is
ambient temperature, sieved at 2 mm and stored in plastic bags for later analyses of soil
about 1500 mm, with constant temperature averaging 26 °C. chemical parameters.
Trials were carried out under farmer conditions, using 2 legume species: Pueraria Earthworm sampling: it was based on TSBF methods (Anderson & Ingram, 1993), 3 soil
phaseoloides (5 plots) and Cajanus cajan (5 plots). For each species, plots were regularly monoliths per plots /Termites sampling: Transect method, 1 per plot/ Nematode sampling:
distributed over the study site and cultivated for 9 months. Then, samplings were carried out for each plot, 5 soil samples were collected from the 0‐20‐cm layer and mixed into a
for soil chemical and biological characterizations, then maize (Zea mays) was cropped on composite sample. Then, nematodes were extracted using an elutriation method.
both the legume and control plots (25m x 25m size), in a side‐by‐side disposition.
RESULTS
Soil chemical characteristics
Table 1: Soil chemical characteristics [mean (SE)] after a 9‐month fallow period
In general, soil chemical parameters were not significantly improved by legume use;
values were rather slightly lower than those under the control (Table 1). This could be due Treatments C N Soluble P CEC Ca2+ Mg2+ K+ pH(H 0) 2
to the fact that (i) soil was denuded with organic matter (SOM) subject to a faster (%) (ppm) (cmolc kg‐1)
mineralization during the first 3 months of legume growth and (ii) the short length of the P. phaseoloides 1.3 (0.1) 0.1 (0.0) 15.5 (3.4) 6.5 (1.2) 3.7 (0.7) 1.8 (0.3) 0.1 (0.0) 6.4 (0.4)
legume‐based fallow period. Control 1.4 (0.0) 0.1 (0.0) 33.7 (17) 7.9 (1.5) 4.6 (1.0) 2.3 (0.5) 0.2 (0.0) 6.8 (0.1)
Earthworms Phytoparasitic Nematodes p (K‐Wallis) ns ns ns ns ns ns ** ns
C. cajan 1.2 (0.1) 0.1 (0.0) 15.6 (3.3) 8.2 (1.5) 4.6 (0.9) 2.4 (0.5) 0.2 (0.1) 6.9 (0.2)
Both Earthworm density and diversity were Legume fallow Natural fallow Control 1.3 (0.1) 0.1 (0.0) 13.8 (2.9) 9.6 (1.2) 5.6 (0.8) 2.7 (0.4) 0.2 (0.0) 6.9 (0.2)
improved under legumes, particularly 10000 p (K‐Wallis) ns ns ns ns ns ns ns ns
9000
under P. phaseoloides (fig. 1 A&B) 8000
D ensity (ind.dm )
-3
7000 Maize Growth and Yield
(A) Treatment Control 6000 a
350
5000 Maize yield was higher on legume than the control plots, though this was not
4000
300 significant when considering grain yield (fig. 4). The values were 310 kg.ha‐1 (i.e. 14 %)
Density (ind. m-2)
3000
250
2000 a on P. phaseoloides and 648 kg.ha‐1 (i.e. 36.4 %) on C. cajan plots, respectively.
200 a a a a
a 1000 a a a a
150 b
0
100
50
Free-living Root-living Free-living Root-living
0 Legume fallow Natural fallow
P. phaseoloides C. cajan
P. phaseoloides C. cajan
12
Maize yields (t.ha -1 )
(B) Treatment Control
Fig. 2: Comparison of pytoparasitic nematode 10 a a
density under legume –bsed and control plots
3 a 8 a b
a a
The number of phytoparasitic nematodes was lower under both legumes 6
2 4
b species, although differences were not significant (fig. 2). This could be a
a
a
a
H'
2
1
partly due to the feeding habits of earthworms (Tao et al., 2009).
0
0
Enzymatic Activities Control Pueraria Tot. Biom Grain Tot. Biom Grain
P. phaseoloides C. cajan
P. phaseoloides C. cajan
No difference was observed between legumes and controls (Table
Fig. 1: Earthworm densities (A) and 2), probably because litter decomposition with legumes was similar Fig. 3: A view of the difference in Fig. 4: Maize yields on legume‐based
diversities (B) under legume fallow maize growth between legume‐ and control plots
and control plots to that in natural Chromolaena odorata fallows (Autfray & Gbaka, based and control plots
1998).
Table 2: Soil enzymatic activities ; [mean (SE)]
Enzymatic activities (μmol pNP g‐1 sol h‐1) CONCLUSION
Treatments
Pac Pal NAG ß‐Glu The improving effect of legumes on soil chemical parameters was not
P. phaseoloides 1.7 (0.2) 1.4 (0.1) 0.2 (0.0) 0.4 (0.0)
Soil fauna and maize yield
observed, probably because the 9‐month legume growth period was
Control 1.7 (0.2) 1.6 (0.2) 0.2 (0.0) 0.3 (0.0) Results revealed significant correlation between
not sufficient. Nevertheless, both earthworm density and diversity
p (t‐test) ns ns ns ns some soil biological parameters and maize yield.
increased, while nematode density was reduced. Maize yield was also
C. cajan 2.0 (0.2) 1.9 (0.1) 0.2 (0.0) 0.4 (0.1) Both total maize biomass and the weight of 100
Control 1.9 (0.2) 1.9 (0.2) 0.4 (0.1) 0.5 (0.1)
improved on legume plots. Besides, significant correlations were
grains correlated significantlywith the number
p (t‐test) ns ns ns ns observed between earthworms and maize yield. Hence, the use of
earthworm species (r=0.80 and r=0.84, respectively)
Pac: acid phosphatase; Pal: alkaline phosphatase; NAG: N‐acétyl‐β‐D‐glucosaminidase; legumes ned to be encouraged in belowground biodiversity
β‐Glu: β‐glucosidase and the Shannon index (r=0.82 and r=0.76,
management programs.
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