Cowpea N rhizodeposition and its below-ground transfer to a co-existing and to a subsequent millet crop on a sandy soil of the Sudano-Sahelian eco-zone

Guillaume Laberge, Bettina I.G. Haussmann, Per Ambus, Henning Høgh Jensen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Nitrogen (N) rhizodeposition by cowpea (Vigna unguiculata (L.) Walp) is potentially a large N source in cropping systems of Sub-Saharan Africa. A field experiment was conducted to measure cowpea N rhizodeposition under the conditions of the Sudano-Sahelian zone using direct 15N labelling techniques to trace the amount of deposition and its transfer to associated and subsequent crops. Half of the total cowpea crop N was located below-ground at plant maturity, which exceeded 20 kg N ha−1 when intercropped with millet. Only 15% of the below-ground cowpea N was recovered in roots, while 85% was found in the rhizodeposited pools. The experiment demonstrated that direct below-ground N transfer occurred from cowpea to millet in intercrop at a rate of 2 kg N ha−1 over the growing season. Forty percent of the 25 kg below-ground N that the cowpea crop left at harvest were identifiable in the top 0.30 m soil in the beginning of the next planting season 7 months later; a pool still present at the end of that second season. Thus, the subsequent crop of millet (Pennisetum glaucum (L.) R. Br.) only recovered 2.5 kg N ha−1 from the below-ground cowpea pre-crop N during this growth season. The role and potential of cowpea as N provider has been underestimated in the past by ignoring the large proportion of N contained in its rhizodeposits. However, information is needed to determine how losses of the rhizodeposited N can be minimized to fully harness the potential of cowpea as N provider in agro-ecosystems of the region.
    Original languageEnglish
    JournalPlant and Soil
    Volume340
    Issue number1-2
    Pages (from-to)369-382
    ISSN0032-079X
    DOIs
    Publication statusPublished - 2011

    Keywords

    • Environment and climate
    • 15N
    • Vigna unguiculata
    • Leaf labelling
    • Legume
    • Nitrogen transfer
    • Tracer
    • Roots
    • Cowpea
    • Pennisetum glaucum
    • N deposition

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