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Accueil du site → Doctorat → Pays-Bas → 2001 → Quantitative understanding of the performance of upland rice - cover legume cropping systems in West Africa

Wageningen Universiteit (2001)

Quantitative understanding of the performance of upland rice - cover legume cropping systems in West Africa

Akanvou, R.K.

Titre : Quantitative understanding of the performance of upland rice - cover legume cropping systems in West Africa

Auteur : Akanvou, R.K.

Université de soutenance : Wageningen Universiteit

Grade : PhD thesis 2001

Reducing the long fallow period by replacing the natural fallow with fast growing legume species to improve soil fertility, control weeds or to grow additional forage necessitate selection of suitable species for those objectives. In three agroecological zone in West Africa, rice grain yield increased by 20 to 30% following legume fallow compared to a natural fallow. Within an agroecological zone, yield differed significantly depending on the management of the cover crop residues. Burning of the residues had a positive effect on yield in the derived savanna zone as well as the Guinea savanna zone. Residue incorporation was superior to farmer’ practice of removing the residues. In contrast to the savanna zones, farmers’ practice of residue burning in the forest zone, produced the highest yield. Basic information on morphology and growth characteristics was collected to compare productivity and competitiveness of six legume cover crop species ( Crotalaria juncea , Cajanus cajan , Mucuna pruriens var. cochinchinensis , Calopogonium mucunoides , Aeschynomene histrix and Stylosanthes hamata ) in monoculture. The most competitive species were identified as the most productive. On average N accumulation was 70 kg ha-1, ranging from 25 kg ha-1for S. hamata and A. histrix to 227 for P . phaseoloides . In the savannah zone of West Africa with a prolonged dry season, the successful growth of legume species as short-season fallow necessitates relay establishment of the cover crops into the preceding food crop. To understand interactions between the components of a relay cropping system and the underlying mechanisms, two contrasting species C. cajan (highly competitive) and S. hamata (less competitive) were intercropped with two rice cultivars WAB56-50 and WAB450-24-3-2-P18-HB syn. V4. Rice biomass and grain yield were significantly (p<0.001) reduced when legumes were established between 0 and 28 days after rice sowing (DARS). The derived yield loss-legume biomass relationship showed that C. cajan was the most suitable legume speciesfor a relay intercropping system with upland rice, as it produced reasonable amounts of biomass at low levels of rice grain yield loss. Further analysis of the results by dynamic modelling of the cropping system revealed that the inferior performance of S. hamata was indirectly caused by its weak competitiveness, which required a relatively early introduction of this legume. The combination of early introduction and short growth duration of this species prevented a rapid leaf canopy development after rice harvest, resulting in a relatively poor biomass production.

Mots clés : oryza sativa - rice - legumes - cropping systems - relay cropping - crop production - systems analysis - simulation models - west africa - agroecosystems

Présentation de la thèse

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