Integrated use of fertilizer micro-dosing and Acacia tumida mulching increases millet yield and water use efficiency in Sahelian semi-arid environment

Limited availability of soil organic amendments and unpredictable rainfall, decrease crop yields drastically in the Sahel. There is, therefore, a need to develop an improved technology for conserving soil moisture and enhancing crop yields in the Sahelian semi-arid environment. A 2-year field experiment was conducted to investigate the mulching effects of Acacia tumida pruning relative to commonly applied organic materials in Niger on millet growth, yields and water use efficiency (WUE) under fertilizer micro-dosing technology. We hypothesized that (1) A. tumida pruning is a suitable mulching alternative for crop residues in the biomass-scarce areas of Niger and (2) combined application of A. tumida mulch and fertilizer micro-dosing increases millet yield and water use efficiency. Two fertilizer micro-dosing options (20 kg DAP ha−1, 60 kg NPK ha−1) and three types of organic mulches (millet straw, A. tumida mulch, and manure) and the relevant control treatments were arranged in factorial experiment organized in a randomized complete block design with four replications. Fertilizer micro-dosing increased millet grain yield on average by 28 %. This millet grain yield increased further by 37 % with combined application of fertilizer micro-dosing and organic mulch. Grain yield increases relative to the un-mulched control were 51 % for manure, 46 % for A. tumida mulch and 36 % for millet mulch. Leaf area index and root length density were also greater under mulched plots. Fertilizer micro-dosing increased WUE of millet on average by 24 %, while the addition of A. tumida pruning, manure and millet increased WUE on average 55, 49 and 25 %, respectively. We conclude that combined application of micro-dosing and organic mulch is an effective fertilization strategy to enhance millet yield and water use efficiency in low-input cropping systems and that A. tumida pruning could serve as an appropriate mulching alternative for further increasing crop yields and water use efficiency in the biomass-scarce and drought prone environment such as the Sahel. However, the economic and social implications and the long-term agronomic effects of this agroforestry tree in Sahelian millet based system have to be explored further

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

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 ofthe 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.© 2010 International Formulae Group. All rights reserved.Keyswords: Land degradation status, indigenous arbuscular mycorhizal, nutrient uptake, millet, acid sandy soi

Desert dust impacts on human health: an alarming worldwide reality and a need for studies in West Africa

High desert dust concentrations raise concerns about adverse health effects on human populations. Based on a systematic literature review, this paper aims to learn more about the relationship between desert dust and human health in the world and to analyse the place of West Africa as a study area of interest. Papers focussing on the potential relationship between dust and health and showing quantitative analyses, published between January 1999 and September 2011, were identified using the ISI Web of Knowledge database (N = 50). A number of adverse health effects, including respiratory, cardiovascular and cardiopulmonary diseases, are associated with dust. This survey highlights obvious dust impacts on human health independently of the study area, health outcomes and method. Moreover, it reveals an imbalance between the areas most exposed to dust and the areas most studied in terms of health effects. None of these studies has been conducted in West Africa, despite the proximity of the Sahara, which produces about half of the yearly global mineral dust. In view of the alarming results in many parts of the world (Asia, Europe, America), this paper concludes by stressing the importance of carrying out impact studies of Saharan dust in West Africa, where dust events are more frequent and intense than anywhere else

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

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