Journal of Animal and Plant Sciences
J. Anim. Plant Sci. [ISSN 2071 - 7024]
Volume 5 (2): 494 - 506. Published December 23, 2009.
Productivity of yams (Dioscorea spp.) as affected by soil fertility
Lucien N’Guessan Diby*,**, Valery Kouamé Hgaza*,***, Tra Bi TIE**, Ayémou Assac†, Robert Carskyd†, Olivier Girardin*, Emmanuel Frossard*****
* Swiss Centre for Scientific Research in Côte d’Ivoire (CSRS), 01 BP 1303 Abidjan, Côte d’Ivoire
**
Département des eaux, forêts et environnement, Ecole Supérieure d’Agronomie, Institut National Polytechnique HB (INP-HB), 01 BP 1313 ESA Yamoussoukro, Côte d’Ivoire
*** Université de Cocody, Abidjan, Côte d’Ivoire
****
The International Institute of Tropical Agriculture (IITA), Cotonou, Benin
*****
Swiss Federal Institute of Technology (ETH Zurich), Institute of Plant Sciences, Eschikon 33, CH-8315 Lindau, Switzerland
* Corresponding author Email: lucien.diby@gmail.com
†: Deceased
SUMMARY
Field experiments were conducted in central Côte d’Ivoire during the growing seasons of 2001, 2002 and 2003 to investigate the effect of natural soil fertility and inorganic fertilizer on productivity of yams. Dioscorea alata cv. TDa 95/00010 and Dioscorea rotundata cv. TDr 98/02461 were grown with and without fertilizer application in a savannah site with a low fertility soil and in a forest site with a more naturally fertile soil. The fresh tuber yield (FTY), the area under the curve (AUC) of shoot and tuber and the AUC of nitrogen and potassium contents all significantly increased in the forest site than in the savannah site. This was due to the greater soil organic matter and exchangeable K, Ca and Mg contents observed at the forest site. The inorganic fertilizer applied had no effect on the FTY, while it significantly increased the AUC of shoot and tuber of D. rotundata in the savannah site. The shoot AUC of D. alata was increased with fertilizer application in the forest site in 2001, but this was not reflected in increased tuber dry matter (DM), suggesting a side effect of the fertilizer on DM balance between above and underground organs. The increase in the canopy establishment and tuber initiation growth phase in D. alata in the savannah site suggests a better adaptation of this species to low fertility soil and might explain its better overall productivity in the experiments. In contrast, the development of D. rotundata was rather fixed allowing a weak adaptation to low fertile soils. The results showed clear importance of soil organic matter in productivity of yams, which is not compensated in soils with low organic matter content by the use of inorganic fertilizers. It is recommended that management practices that favour maintenance or build up of soil organic matter content be evaluated and applied in yam production systems.
Key words: Area under the curve (AUC), Cote d’Ivoire, forest and savannah transition zone, soil fertility, inorganic fertilizer, yams growth phases
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