Sorghum responses to different forms of Tilemsi rock phosphate combined with soluble fertilizers in a low-input production system in Mali

The deficiency in bioavailable phosphorus is one of the major constraints to cereal production in Mali. The objective of this study was to assess the combined effects of Tilemsi rock phosphate (PNT) with different doses of soluble fertilizers on the solubility of rock phosphate, the agronomic performance of sorghum and the chemical properties of the soil. The study consisted of the comparison of four (4) types of fertilization at three (3) levels of variation 0 kg.ha-1; 11 kg.ha-1, and 16 kg.ha-1 of phosphorus arranged in a complete randomized block with three replicates. The combination of PNT with sulfate ammonium (NH4) 2SO4 resulted in a significant increase in grain and biomass yields during the two years of the study. The increase of the rate of phosphate rock application lead to improve the sorghum grain yield by an average of 29%. The combined application of sulfate ammonium (NH4) 2SO4 with PNT significantly increased the phosphorus uptake indices from PNT. These results show that there is a possibility of improving the productivity of sorghum in Mali with the combined use of Tilemsi rock phosphate and soluble fertilizers, particularly sulfate ammonium. La déficience en phosphore assimilable du sol est l’une des contraintes majeures à la production céréalière au Mali. L’objectif de cette étude est d’évaluer les effets de différentes formules de fumures à base du phosphore naturel de tilemsi (PNT) et d’engrais azotés et potassiques sur les propriétés chimiques du sol et les performances agronomiques du sorgho. Pour ce faire, un dispositif factoriel en blocs complètement randomisés a été implanté. Le premier facteur est composé des 4 formules de fumures (PNT granule (P), PNT granule avec KCl , PNT granule avec (NH4)2SO4 et PNT granule avec KCl et (NH4)2SO4 ) et le second facteur les niveaux de doses de phosphore (0 kg.ha-1; 11 kg.ha-1, et 16 kg.ha-1). L’association du PNT avec le sulfate d’ammonium (NH4)2SO4 a entraîné une augmentation significative des rendements grain et biomasse pendant les deux annéesd’étude. L’augmentation de la dose d’apport du phosphore a amélioré le rendement grain de 29% en moyenne. L’application combinée du sulfate d’ammonium (NH4)2SO4 avec le PNT a augmenté significativement l’efficacité agronomique du PNT. Ces résultats montrent qu’il y a une possibilité d’améliorer la productivité du sorgho au Mali avec l’utilisation combinée de phosphore naturel de Tilemsi à la dose de 16 kg.ha-1 et les engrais solubles notamment le sulfate d’ammonium. Ainsi cette formulation pourrait être recommandée en culture de sorgho pour les producteurs à faible revenu en zone Sahélienne du Mali

Alley Cropped Gliricidia sepium (Jacq.) Kunth ex. Walp. Enhance Soil Fertility and Yields of Cotton, Maize and Sorghum in Mali

Mineral fertilizers are effective in boosting crop yields in most parts of the world. Under tropical conditions and especially in rain-fed arid ecosystems they are not effective, because the limitations of system productivity are stronger at the level of the climatic situation and soil quality. The positive effect of Glirici-dia sepium (G. sepium) for: erosion control, shade, hydraulic lift, N-fixation, resource of fodder and soil input convinced the participating farmers to provide part of their land for this study. G. sepium was tested in association with cotton, maize and sorghum in order to develop best practices at two research stations and on fields of 30 farmers in the Sudanese and Sudano-Guinean zones of Mali. In addition to the introduction of G. sepium, the effects of organic and mineral ferti-lizers we tested at recommended and half rate. On-station experiments design was a split-plot with four replicates. The pH, soil organic carbon and nitrogen in soil samples were analyzed from 0-20 cm depth taken in 2016 at the beginning of the experiment and in 2018. The average yields of cotton, maize and sorghum associated with G. sepium were 812, 1,457 and 1,377 kg ha-1 respectively, whe-reas they were significantly lower without G. sepium reaching only 623, 1,014, and 807 kg ha-1 respectively. In the third year after planting G. sepium, organic carbon contents and total soil nitrogen increased by 5% in soils between the al-leys. Association of G. sepium with cotton, maize, and sorghum showed the im-provement of crop yields and soil nitrogen content in addition to other advantag-es not considered for testing here. This finding may serve to improve small-scale farmer’s livelihoods status through the improvement of soil fertility in Mali and the whole Sahel region