Effets des composts à base de déchets d’agrumes et du tourteau de karité sur la disponibilité du phosphore du sol: Une étude en conditions contrôlées

Le compost, riche en matière organique, contient des éléments fertilisants tels que le phosphore, l’azote et le potassium. La biodisponibilité de ces éléments fertilisants du compost dans le sol dépend de la minéralisation de la matière organique mais aussi des réactions de fixation de ces éléments. Ce travail vise à étudier la disponibilité du phosphore de deux composts: le compost CA obtenu à base des déchets d’agrumes et le compost CK obtenu à base du tourteau de karité. Les composts sont mélangés au sol à raison de 0,5 g de compost pour 50 g de sol et sont incubés dans des conditions contrôlées pendant 180 jours. L’humidité a été ajustée à 2/3 de la capacité au champ et la température à 28 °C. Entre le début et 180 jours d’incubation, une augmentation de 33, 25 et -2% de la teneur en phosphore assimilable est notée pour les traitements sol+CA, sol+CK et le témoin respectivement et près de 85% du phosphore des composts sont disponibles. L’étude de la dynamique du phosphore montre qu’une partie du phosphore s’immobilise sous forme de phosphore lié à l’aluminium. Ceci est plus notable dans le traitement avec le compost CK.Mots clés: disponibilité du phosphore, compost, sol, conditions contrôlée

Exploiting Biological Nitrogen Fixation: A Route Towards a Sustainable Agriculture

For all living organisms, nitrogen is an essential element, while being the most limiting in ecosystems and for crop production. Despite the significant contribution of synthetic fertilizers, nitrogen requirements for food production increase from year to year, while the overuse of agrochemicals compromise soil health and agricultural sustainability. One alternative to overcome this problem is biological nitrogen fixation (BNF). Indeed, more than 60% of the fixed N on Earth results from BNF. Therefore, optimizing BNF in agriculture is more and more urgent to help meet the demand of the food production needs for the growing world population. This optimization will require a good knowledge of the diversity of nitrogen-fixing microorganisms, the mechanisms of fixation, and the selection and formulation of efficient N-fixing microorganisms as biofertilizers. Good understanding of BNF process may allow the transfer of this ability to other non-fixing microorganisms or to non-leguminous plants with high added value. This minireview covers a brief history on BNF, cycle and mechanisms of nitrogen fixation, biofertilizers market value, and use of biofertilizers in agriculture. The minireview focuses particularly on some of the most effective microbial products marketed to date, their efficiency, and success-limiting in agriculture. It also highlights opportunities and difficulties of transferring nitrogen fixation capacity in cereals

Extractions et caractérisations physico-chimiques des substances humiques naturelles des sols et du compost

Les substances macromoléculaires naturelles qui constituent la matière organique (MO) des sols sont formées essentiellement au cours des processus de dégradation des matières végétales et animales par les microorganismes. Elles jouent un rôle dans la fertilisation, le transport, l’immobilisation et la dégradation des espèces chimiques organiques ou minérales telles que les pesticides, les composés aromatiques polycycliques ou les métaux lourds dans les sols et les eaux. Elles doivent ces rôles à leurs caractéristiques chimiques et structurales. D’un milieu à un autre, leurs structures et leurs caractéristiques diffèrent en fonction de conditions physico-chimiques telles que le pH, le taux d’humidité, la température, la composition chimique etc. Dans le cadre de l’étude de la dissolution des phosphates naturels de Hahotoé-Kpogamé (Togo) par les acides organiques naturels, nous avons réalisé l’extraction des substances humiques d’un sol et d’un compost à l’aide d’une solution alcaline de NaOH (0,1 N) après un prétraitement aqueux ou acide. Les échantillons extraits ont été purifiés par dialyse. La caractérisation de ces substances par des méthodes chimiques (dosages élémentaires et du Carbone Organique Total (COT)) et physiques (Spectroscopies Infrarouge et UV-Visible, Microscopie Electronique à Balayage (MEB)) a été effectuée. Les méthodes analytiques utilisées ont permis d’identifier les groupements fonctionnels qui confirment le caractère humique des échantillons extraits.Mots clés : Substances humiques, extraction, caractérisation, infrarouge, UV-Visible, Microscopie Electronique à Balayage (MEB)

Étude de la compétitivité de complexation des métaux issus des phosphates naturels de Hahotoé-Kpogamé par les substances humiques

Le phosphate naturel de par sa formule chimique constitue une source importante de l’élément phosphore pour les plantes. Pour cela il est utilisé dans le compost pour améliorer les qualités nutritionnelles des plantes. Les analyses chimiques effectuées sur le phosphate naturel révèlent la présence des métaux lourds. Pour étudier les risques de rétrogradation de ces engrais phosphatés, notre étude s’est portée sur la complexation des substances humiques naturelles extraites des sols sur des ions métalliques tels que le calcium, cadmium et le magnésium contenus dans les phosphates naturels de Hahotoé- Kpogamé du Togo. Les résultats obtenus montrent que la quantité d’ions complexés augment avec le temps d’attaque. Le taux d’ions complexés diminue lorsque le pH de la solution d’acide humique évolue de 6,5 à 9,5. Une étude comparative de la complexation de ces trois ions révèle que le cadmium malgré sa faible teneur dans le phosphate naturel se complexe mieux que le calcium et le magnésium. Après 30 jours d’attaque du phosphate naturel nous avons obtenu un taux avoisinant les 10% pour le cadmium, 9% pour le calcium et environ 2% pour le magnésium pour une solution d’acide humique de pH=6,5.Mots-clés : complexation, métaux lourds, phosphate naturel, rétrogradation, substances humiques.Study on competitiveness of metals after complexation of phosphate rock in Hahotoè-Kpogamé by humic substancesPhosphate by its chemical constitution is an important source of the phosphorus element for plants. Thus, it is used in compost to improve the nutritional qualities of plants. Chemical analyzes of the phosphate reveal the presence of heavy metals. To assess the risk of the phosphate fertilizer downgrading, our study focused on calcium, magnesium, and cadmium ions contents in the humic substances extracted from soils fertilize with Hahotoè-Kpogamé (Togo) phosphate. The results show that the amounts of ions in the complexed humic substances increase with the attack time. The complexed ions rate decreases as the pH of the solution of humic acid changes from 6.5 to 9.5. Despite the low cadmium content in the rock phosphate, this element is more easily assimilated in complex than its two analogous. After 30 days of phosphate attack, a humic acid solution at pH = 6.5 gave a rate of about 10% for cadmium, 9% for calcium and 2% magnesium.Keywords : complexation, heavy metal, rock phosphate, downgrading, humic substances

Assessment of organo-mineral fraction during co-composting of sewage sludge-lignocellulosic waste by XRD and FTIR analysis

This investigation focuses mainly on highlighting the contribution of the IR spectrum of the mineral matrix in co-composts after removing the organic phase by slow pyrolysis. The mineral matrix is still confusion subject in the interpretation of FTIR spectra of co-composts. The XRF and XRD analysis of the low pyrolysis substrates of sewage sludge and date palm waste during six months of co-composting, show that the mineral fraction is homogeneous in the samples and that the inorganic matrix consists mainly of silica and carbonates including a residual portion remaining after pyrolysis.The comparison of FTIR spectra of heated samples at 105°C and 650°C shows that the 3500-3280 cm-1 region characterises essentially the hydroxyl groups OH (ν(OH)) of water molecules. The observed bands in this region provide information on the co-compost hydrophilic nature but can only provide limited information about the humic substances composition. The band at 1035 cm-1, assigned commonly to organic material, which persists after the thermal treatment, should be assigned for the Si-O vibration of silica

Complexation du Ca++ par les substances humiques extraites de tourbe naturelle et de tourbe traitée aux oxydes d'azote

The study of the complexation of calcium by humic substances (SH) extracted from a natural peat (TN) and from a peat treated with nitrogen oxides (TT) was followed by conductimetry and potentiometry with pH variable and pH constant. The complexing capacity increases as the pH rises: complexed calcium is 130 cmol kg*[-1) SH (TN) and 135 cmol kg*[-1) SH (TT) with pH 5, and 330 cmol kg*[-1) SH (TN) and 410 cmol kg*[-1) SH (TT) with pH 9. These reactions involve various functional groupings of pKa1 < 4 for TN and TT, pKa2 = 5.9 for TN and pKa2 = 6.2 for TT; in all cases, the medium has exhibited an increase in acidity. The complexation of calcium by HS extracted from TT could then enhance the efficiency of the phosphatic nutrition of plants

Applications of quark-hadron duality in F2 structure function

Inclusive electron-proton and electron-deuteron inelastic cross sections have been measured at Jefferson Lab (JLab) in the resonance region, at large Bjorken x, up to 0.92, and four-momentum transfer squared Q2 up to 7.5 GeV2 in the experiment E00-116. These measurements are used to extend to larger x and Q2 precision, quantitative, studies of the phenomenon of quark-hadron duality. Our analysis confirms, both globally and locally, the apparent violation of quark-hadron duality previously observed at a Q2 of 3.5 GeV2 when resonance data are compared to structure function data created from CTEQ6M and MRST2004 parton distribution functions (PDFs). More importantly, our new data show that this discrepancy saturates by Q2 ~ 4 Gev2, becoming Q2 independent. This suggests only small violations of Q2 evolution by contributions from the higher-twist terms in the resonance region which is confirmed by our comparisons to ALEKHIN and ALLM97.We conclude that the unconstrained strength of the CTEQ6M and MRST2004 PDFs at large x is the major source of the disagreement between data and these parameterizations in the kinematic regime we study and that, in view of quark-hadron duality, properly averaged resonance region data could be used in global QCD fits to reduce PDF uncertainties at large x.Comment: 35 page

Transverse momentum dependence of semi-inclusive pion production

Cross sections for semi-inclusive electroproduction of charged pions ($\pi^{\pm}$) from both proton and deuteron targets were measured for $0.2<x<0.5$, $2<Q^2<4$ GeV$^2$, $0.3<z<1$, and $P_t^2<0.2$ GeV$^2$. For $P_t<0.1$ GeV, we find the azimuthal dependence to be small, as expected theoretically. For both $\pi^+$ and $\pi^-$, the $P_t$ dependence from the deuteron is found to be slightly weaker than from the proton. In the context of a simple model, this implies that the initial transverse momenta width of $d$ quarks is larger than for $u$ quarks and, contrary to expectations, the transverse momentum width of the favored fragmentation function is larger than the unfavored one.Comment: 15 pages, 4 figures. Fit form changed to include Cahn effect Minor revisions. Added one new figur

The Onset of Quark-Hadron Duality in Pion Electroproduction

A large data set of charged-pion electroproduction from both hydrogen and deuterium targets has been obtained spanning the low-energy residual-mass region. These data conclusively show the onset of the quark-hadron duality phenomenon, as predicted for high-energy hadron electroproduction. We construct several ratios from these data to exhibit the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark-to- pion production mechanisms.Comment: 11 pages, 3 figures, accepted in Phys. Rev. Lett. Tables adde