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Browsing by Author "Oliver, R."

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  • Alley cropping of maize and Gliricidia sepium in the Sudanese Sahel Region: Some technical feasibility aspects
    Ndiaye, M.; Ganry, F.; Oliver, R. (Taylor and Francis Ltd, 2000)
    An association in an alley cropping experiment of a short-term maize variety and a tree legume (Gliricidia sepium) adapted to the Sudanese Sahel region was studied from the point of view of the nitrogen balance and plot yields. Isotopic labeling applied in the field enabled the contribution to maize nitrogen nutrition from different nitrogen sources (fertilizer, prunings, and soil) to be quantified. For equal cultivated areas, alley cropping provides a maize yield greater than that of maize grown in pure stand without nitrogen fertilizer. However this yield is only 40% of that obtained in pure stands with fertilizer nitrogen. Alley cropping gives a very favourable Land Equivalent Ratio (LER) of 0.90 and 1.58 compared with N-fertilized and non-N-fertilized plots, respectively. These LERs demonstrate the increased biological efficiency of the cultivated soil in an agroforestry system. The percentage of the total nitrogen in the maize coming from prunings (Nfdp) varies between 30 and 35% and the true coefficient of nitrogen utilization of the prunings (TCUp) varies from 15-25%. In the environment of central Senegal, the percentage of total nitrogen of G. sepium coming from N2 fixation is quite low (Ndffix = 25%), and consequently, in the maize, the nitrogen coming from N2 fixation (Ndffix) is only 8%. It is therefore necessary to improve the efficiency of nitrogen fixation of G. sepium in this zone to assure the sustainability of the agroforestry system. ---Journal/Author's Abstract
  • Effect of a legume cover crop (Mucuna pruriens var. utilis) on soil carbon in an Ultisol under maize cultivation in southern Benin
    Barthès, Bernard G.; Azontonde, A.; Blanchart, E.; Girardin, C.; Villenave, C.; Lesaint, S.; Oliver, R.; Feller, C. (Ingenta, 2004)
    Long term fallow is no longer possible in densely populated tropical areas, but legume cover crops can help maintain soil fertility. Our work aimed to study changes in soil carbon in a sandy loam Ultisol in Benin, which involved a 12-year experiment on three maize cropping systems under manual tillage: traditional no-input cultivation (T), mineral fertilized cultivation (NPK), and association with Mucuna pruriens (M). The origin of soil carbon was also determined through the natural abundance of soil and biomass 13C. In T, NPK and M changes in soil carbon at 0-40 cm were -0.2, +0.2 and +1.3 t C ha^(-1) yr^(-1), with residue carbon amounting to 3.5, 6.4 and 10.0 t C ha^(-1) yr^(-1), respectively. After 12 years of experimentation, carbon originating from maize in litter-plus-soil (0-40 cm) represented less than 4% of both total carbon and overall maize residue carbon. In contrast, carbon originating from mucuna in litter-plus-soil represented more than 50% of both total carbon and overall mucuna residue carbon in M, possibly due to accelerated mineralization of native soil carbon (priming effect) and slow mulch decomposition. Carbon originating from weeds in litter-plus-soil represented c. 10% of both total carbon and overall weed residue carbon in T and NPK. Thus mucuna mulch was very effective in promoting carbon sequestration in the soil studied.