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1.
J Agric Food Chem ; 66(19): 4787-4799, 2018 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-29677445

RESUMO

This study describes the efficiency of a new coating material for preparing granulated potassium-fertilizers with a potassium release to the soil solution sensitive to rainfall intensity. The composite is prepared by reaction of an alkyd-resin with cement in the absence of water. The complementary use of diverse analytical techniques showed that the presence of the cement fraction induced alkyd resin reticulation and gradual cement-resin hardening. Scanning electron microscopy revealed the formation of micro and nanopores within cement-clusters, whose water permeability is affected by the resin reticulation and amphiphilic character. Potassium release was evaluated in water, soil-columns, and in soil-plant trials in pots and open-field. Agronomic results were consistent with potassium release rates obtained in water solution and soil columns. The composite-coated potassium fertilizer was more efficient than the noncoated one in providing plant available potassium, with this effect being dependent on water presence in soil.


Assuntos
Produtos Agrícolas/crescimento & desenvolvimento , Composição de Medicamentos/métodos , Fertilizantes/análise , Potássio/química , Produtos Agrícolas/efeitos dos fármacos , Cinética , Potássio/farmacologia , Solo/química , Água/análise
2.
J Sci Food Agric ; 93(2): 293-303, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22740371

RESUMO

BACKGROUND: Previous studies showed that phosphate can be complexed by humic acids (HA) through stable metal (M) bridges (PMHA). We studied the thermodynamic properties of PMHA and their relationships with the ability of PMHA to both decrease soil P fixation and increase P availability for plants. With this aim, we studied the theoretical stability of PFeHA, PAlHA and PCaHA by molecular modelling methods in relation to the degree and intensity of P absorption in soils and the ability of plants to take up complexed P. RESULTS: A density functional theory (DFT) quantum chemical study enabled us to obtain stable structures for the three PMHA complexes in water solution. The theoretical stabilities (ΔG°) were consistent with that for apparent stability obtained by Scatchard method, PFeHA ≥ PAlHA > PCaHA, though the differences were clearer by the DFT method. Also the reduction of soil P fixation and the release of P from PMHA in the presence of an anionic resin confirmed the stability order of the different PMHA. Plant studies confirmed the ability of diverse plant species to take up both P and metal complexed in PMHA. CONCLUSION: The results indicated the potential efficiency of PMHA-based fertilizers to optimize P fertilization for crops cultivated in soils with high P fixation ability.


Assuntos
Alumínio/metabolismo , Cálcio/metabolismo , Produtos Agrícolas/crescimento & desenvolvimento , Fertilizantes , Ferro/metabolismo , Modelos Moleculares , Fósforo/metabolismo , Alumínio/química , Cálcio/química , Quelantes/química , Quelantes/metabolismo , Cicer/crescimento & desenvolvimento , Cicer/metabolismo , Produtos Agrícolas/metabolismo , Fertilizantes/análise , Substâncias Húmicas/análise , Ferro/química , Cinética , Fosfatos/química , Fosfatos/metabolismo , Teoria Quântica , Solo/química , Espanha , Triticum/crescimento & desenvolvimento , Triticum/metabolismo
3.
J Agric Food Chem ; 56(3): 1035-42, 2008 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-18205313

RESUMO

Previous studies demonstrated the formation of stable phosphate-metal-humic complexes in solution. These studies, however, indicated that the proportion of complexed metal that intervenes in phosphate fixation is rather low. In this study we investigate the possible structural and electronic features of the binding site involved in phosphate fixation in metal-humic complexes that could explain this fact. To this end, we have studied phosphate-metal-humic complexes involving Fe(III), Al(III), and Zn(II) using three complementary techniques: infrared spectroscopy (FTIR), fluorescence, and molecular modeling. The FTIR study indicated that, in the case of those complexes involving Fe and Zn phosphate, fixation is associated with a stabilization of the metal-carboxylate bond. In the case of Al this effect is less clear. This effect of phosphate fixation on the characteristics of the metal-humic binding site was also supported by the results obtained in the Fluorescence study, which showed significant changes in the quenching effect normally associated with metal complexation in humic substances upon phosphate fixation. Finally, the molecular modeling study revealed that the stability of phosphate-metal-humic complexes is inversely related to the stability of the metal-humic interaction. This result could explain why only a relatively low proportion of humic complexed metal is involved in phosphate fixation.


Assuntos
Substâncias Húmicas/análise , Metais/química , Fosfatos/química , Alumínio/química , Sítios de Ligação , Fenômenos Químicos , Físico-Química , Ferro/química , Modelos Moleculares , Espectrometria de Fluorescência , Espectroscopia de Infravermelho com Transformada de Fourier , Zinco/química
4.
J Agric Food Chem ; 53(22): 8673-8, 2005 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-16248570

RESUMO

The aim of this work is to study the suitability of the complementary use of ultrafiltration (UF) and the interaction with an anion-exchange resin (AR) to characterize of phosphate-metal-humic complexes in solution. The results indicate that a methodological approach consisting of the validation and calibration of the AR method by the UF method and the further use of the AR method is suitable for characterizing phosphate-metal complexes. Such an approach has proven to be useful for calculating the phosphate maximum binding capacity of iron-humic complexes and stability constants. It might also be used to obtain valuable purified phosphate-metal-humic complexes for further structural characterization.


Assuntos
Substâncias Húmicas , Metais/química , Fosfatos/química , Ânions , Fenômenos Químicos , Físico-Química , Estabilidade de Medicamentos , Resinas de Troca Iônica/química , Soluções , Ultrafiltração
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