Contribution of arbuscular mycorrhizal fungi to pearl millet [Pennisetum glaucum (L.) R. Br.] nutrition on Sahelian acid sandy soils at various levels of soil degradation

Abstract

Land degradation may cause nutrient deficiencies for plant growth. These deficiencies can be partly compensated through plant association with arbuscular mycorrhizal (AM) fungi under the condition that the degradation status does not affect the symbiosis. We therefore investigated P and K uptake by millet [Pennisetum glaucum (L.) R. Br.] roots when associated with AM fungi from an acid sandy soil of the Sahel at 3 different levels of soil degradation. Millet was grown in an eight-week greenhouse pot experiment. Nutrient uptake was quantified on the basis of nutrient depletion in P and K-enriched soil tubes accessible to roots and hyphae or solely to hyphae compared to tubes inaccessible to roots and hyphae. Neither total millet biomass nor root colonisation frequency differed between the weakly and the medium degraded soils. However, total millet biomass and root colonisation frequency were 61% and 40% lower, respectively, on the severely degraded soil compared to the other two degradation levels (weakly and medium). Irrespective of the soil degradation status, AM fungi alone depleted total soil P by 24 mg P kg-1 soil but they had very little effect on exchangeable K+ levels. AM fungi maintained their potential to contribute to millet P nutrition, irrespective of
the soil degradation status. On severely degraded soils, the mycorrhizal fungi's contribution to millet nutrition may be depressed to some extent but not sufficiently to impact P uptake by hyphae once they have access to P inaccessible to roots.
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Keyswords: Land degradation status, indigenous arbuscular mycorhizal, nutrient uptake, millet, acid sandy soil