In the Sahel, mineral fertilizer micro-dosing technique is known for its benefits to provide higher nutrient uptake and higher crop yields. A study was set up at ICRISAT research station at Sadoré in Niger, which aims at evaluating the sustainability of the technology in the longterm with emphasis on soil nutrients dynamics. The study has started since 2008 and was laid-out in a randomized complete block design that involved two pearl millet varieties, three planting densities, and four nutrients management options. For this study, a subset of the treatments from this long-term experiment was used. The nutrient management factor, which includes 4 levels was considered. The most important findings obtained indicated that the change in soil nutrient was markedly different on the planting hills and that from between hill. The change in soil pH-H2O values on the planting was-7.06 % for the control plots and-9.57 % for the plots applied with NPK. The total nitrogen content has dropped in the two different plots. The amplitude of drop has lowered with the application of NPK micro-dosing on the planting hills with respectively-5.11 % and-12.45 % in the control plots and the micro-dose plots. Positive change in available P was significantly observed (P≤0.05) in soil between hill with 1.08% in the control plots and 15.97 % in the amended plots. Both grain yield and total dry matter showed similar trend in which decreased yield was obvious over the time. In 2008, an average grain yield of 732 kg. ha-1 and 989 kg. ha-1 was obtained respectively for the control plots and 6g per hill of NPK plots. Whereas in 2016, 146 kg. ha-1 and 218 kg. ha-1 were produced respectively for the control plots and the mineral fertilizer micro-dosing plots. These findings indicated that in the Sahel low-input based millet cropping systems, for the mineral fertilizer micro-dosing technology to be sustainable in the long term, the improvement and maintenance of soil fertility should be considered as the cornerstone.

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.

To improve synchronicity between nutrients released from the decomposing manure with millet nutrient requirement under zaï technique, a 2-year field experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics Research Station, Sadoré, Niger. The treatments consisted of factorial combination of two rates of cattle manure (200 and 300 g per zaï hole), three periods of manure application (before planting, at planting and 15 days later) and two rates of mineral fertilizer [nitrogen (N), phosphorus (P) and potassium (K) 15-15-15] applied at 6 g per zaï hole and a control, without mineral fertilizer). Manure dry mass losses did not significantly differ among manure application periods in 2013. However, in 2014 the highest manure dry mass loss occurred when manure was applied before planting with 70% of manure applied being decomposed at millet maturity stage (115 days after litterbag installation) followed by manure applied at planting with almost 50% of dry mass losses. The quantities of N and P absorbed by millet at tillering stage represented, 61, 52 and 33% of N released and 15, 12 and 15% of P released at the same time when manure was applied before planting, at planting and 15 days after planting, respectively. Application of manure before planting increased on an average millet grain yield by 16 and 20% and N utilization efficiency by 25 and 31% compared to application of manure at planting and 15 days after planting respectively. Addition of mineral fertilizer induced a synergetic effect on millet grain yield (p = 0.002). Millet grain yields increased on average by 5, 17 and 57% when 6 g per zaï pit of NPK fertilizer were added to plots receiving manure application before planting, at planting and 15 days after planting, respectively. We conclude that application of manure prior to planting satisfies better millet nutrients demand, thereby increasing nutrient use efficiency and grain yield under zai pits.

The concentrations of some heavy metals (Cd, Cr and Pb) were determined in top soil and (Amaranthus caudatus) samples from irrigated farmlands in Yamaltu, Gombe State, Nigeria, using Atomic Absorption Spectrophotometer (AAS). The results show that the heavy metals contents were higher in the soil than in the amaranths. The results also revealed the trend in soil metals concentration as Cd > Pb > Cr and for the plant as Cd > Cr > Pb. Transfer factors (TF) decreased in the following order: Cd > Pb > Cr respectively. The levels of toxic metals are within the tolerable levels except for Cd in Amaranthus caudatus which are higher than the Indian Standard recommended values (1.5 mg kg-1) for human consumption. The high level of Cd place the consumers of this vegetable crop grown within the area at health risk with time unless an urgent step is taken to address this issue.

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