Estudio de la fracción húmica de diferentes fertilizantes húmicos comerciales

29 páginas.-- 2 figuras.-- 5 tablas.-- 13 referencias.-- Memoria del XXXIX Curso Internacional de Edafología y Biología VegetalDurante las últimas décadas la presión económica así como la creciente demanda de alimentos, ha dado lugar a la explotación de cultivos intensivos a gran escala, utilizando cada vez mayores cantidades de fertilizantes químicos inorgánicos y contemplando solamente la nutrición de los cultivos a corto plazo, olvidando cada vez más, el factor "natural" de la fertilidad misma de los suelos. La materia orgánica, junto con el aire, agua y minerales, es uno de los componentes básicos del suelo. Se define como el conjunto de componentes orgánicos, de origen animal o vegetal, que se encuentra en diferentes estados de descomposición o transformación. La materia orgánica es una porción del suelo aún y cuando la mayoría de los cultivos contienen solamente de 1 a 5 % de materia orgánica (en su capa superficial), esa pequeña cantidad modifica las propiedades fisicas del suelo y afecta fuertemente sus propiedades químicas y biológicasPeer reviewe

Uso potencial de arcillas modificadas con metales para la obtención de formulaciones de liberación lenta de herbicidas.

9 páginas., 5 gráficos, 2 tablas y 9 referencias. Versión extendida de la comunicación presentada en la "XIX Reunión Científica de la Sociedad Española de Arcillas - SEA05", celebrada en Salamanca del 26 al 28 de Septiembre de 2005. Enlace a la web de la Sociedad Española de Arcillas http://www.sea-arcillas.es/publicacionesSEA.htm[EN]Abstract A slow release system of the herbicide imazapyr was designed by adsorption on pillared clays. Pillared clays based on aluminum and mixed aluminum-copper solutions were synthesized. The aim was to check whether the introduction into the pillars of a metal complexing the herbicide molecules enhanced the sorption and release properties of the clay for the herbicide. A commercial aluminum pillared clay was also examined as a potential sorbent. The chemical analysis data as well as those of X-ray diffraction show that copper from pillaring solutions was partially introduced, and the basal spacing were increased about 9 Å in good agreement with the size of the Keggin ion. The textural properties indicate a reduction in the micro- and mesoporosity of the pillared clays after pillaring with copper solutions. The largest the copper content in the mixed Al-Cu pillared clays the largest the decrease in the surface area. However, imazapyr adsorption increased up to three-fold compared to the commercial pillared clay, and desorption percentages from the Cu-Al pillared clays were three-fold lower than the commercial one, whose desorption was completely reversible. These preliminary results show the potential use of Cu-Al pillared clays for the development of slow release formulations of the herbicide imzapyr, unlike those whose pillars are only made of aluminum.[ES]Resumen En el presente trabajo se ha intentado desarrollar un sistema de liberación lenta del herbicida imazayr mediante su adsorción en arcillas pilareadas. Se han sintetizado arcillas pilareadas con aluminio y con soluciones mixtas Cu-Al, a fin de comprobar si la formación de pilares mixtos de aluminio con un metal complejante del herbicida mejoraba las propiedades de adsorción y liberación del mismo. También se ha estudiado el empleo potencial de una arcilla pilareada comercial formada con pilares exclusivos de aluminio. Los resultados de análisis químico así como de difracción de rayos X muestran que parte del cobre de las soluciones pilareantes se ha introducido en las arcillas finales, cuyos espaciados basales presentan un incremento de aproximadamente 9 Å, que se corresponde con el tamaño del ión Keggin. Las propiedades texturales indican una disminución tanto de la microporosidad como de la mesoporosidad en las arcillas tras su pilarización con soluciones de Cu-Al, que es tanto mayor cuanto mayor es el contenido de Cu. A pesar de la reducción en la superficie de estas arcillas sintetizadas con Cu, la adsorción de imazapyr incrementaba hasta 3 veces con respecto a la arcilla pilareada comercial. A su vez los porcentajes de desorción en la arcillas pilareadas con Cu-Al eran hasta tres veces inferiores a los correspondientes a la arcilla pilareada comercial, cuya desorción era prácticamente reversible. Estos resultados preliminares avalan el uso potencial de arcillas pilareadas con Cu-Al para el desarrollo de formulaciones de liberación lenta del herbicida imazapyr, a diferencia de aquellas en las que los pilares se encuentran formados únicamente por aluminio.Peer Reviewe

Formulaciones de liberación lenta de herbicidas mediante el uso de complejos mineral de la arcilla-liposomas

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Effect of organic amendments on the retention and mobility of imazaquin in soils

8 pages, 1 scheme, 2 figures, 7 tables, 39 references.The influence of two organic amendments consisting of an urban waste compost (SUW) and a commercial amendment from olive mill wastes (OW) was assessed on the sorption properties and leaching of the ionizable herbicide imazaquin on four soils with different physicochemical characteristics. A loamy sand soil (CR), a loam soil (P44), a silt loam soil (AL), and a clay soil (TM), with low-medium organic matter contents, were chosen. Sorption-desorption experiments were performed on the original soils and on a mixture of these soils with the organic amendments at a rate of 6.25% (w/w). These mixtures were used just after preparation and after aging for 3 months. Imazaquin adsorption was higher on AL soil because of its high content of amorphous iron oxides, whereas it was related to the soils’ organic matter (OM) contents on TM and CR soils and to acid pH on P44 soil. Addition of exogenous OM to soils caused a decrease in the adsorption of the herbicide with the only exception of CR soil, due to blocking of adsorptive surfaces and/or equilibrium pH rise. The extent of this decrease was dependent only on the nature of the added amendment on AL soil. The adsorbed amounts of imazaquin on aged organic fertilized soils were usually fairly close to that on original soils. Results of soil column experiments indicate that addition of exogenous organic matter cannot be considered as a regular practice for retarded movement of imazaquin.Acknowledges the Spanish Ministry of Science and Technology for a Ramon y Cajal research contract. We acknowledge the Spanish government for financial support under Projects AGL2000-0493-C02-01 and AGL2002-00993.Peer reviewe

Interacciones montmorillonita-fosfatidilcolina para el desarrollo de formulaciones de liberación lenta de herbicidas

2 páginas, 3 figuras.El uso de plaguicidas es esencial para la producción necesaria de alimentos a nivel mundial. Al alcanzar el suelo, los plaguicidas pueden sufrir pérdidas por procesos de disipación, escorrentías superficiales, lixiviación a lo largo del perfil del suelo, etc. Esto implica una reducción en la eficacia de las formulaciones convencionales que deben ser usadas a mayores dosis para minimizar estas pérdidas, con los consiguientes costes tanto económicos como medioambientales.Peer reviewe

Environmentally friendly slow release formulations of alachlor based on clay-phosphatidylcholine

6 pages, 3 tables, 4 figures, 22 references.A new clay-liposome complex was developed for reducing leaching of herbicides and contamination of groundwater. The liposomes were composed of the neutral and Environmental Protection Agency approved phospholipid phosphatidylcholine (PC). Adsorption of PC liposomes on the clay mineral montmorillonite could exceed the cation exchange capacity of the clay, and was well simulated by the Langmuir equation. X-ray diffraction results for 6 mM PC and 1.6 g/L clay (3 day incubation) yielded a basal spacing of 7.49 nm, which was interpreted as the formation of a supported planar bilayer on montmorillonite platelets. Fluorescence methods demonstrated structural changes which reflected adsorption of PC followed by loss of vesicle integrity as measured by the penetration of dithionite into the internal monolayer of fluorescently labeled liposomes, resulting in a decrease in fluorescence intensity to 18% of initial after 4 h. Energy transfer was demonstrated after 1 h from labeled liposomes to montmorillonite labeled by an acceptor. The neutral herbicide alachlor adsorbed on the liposome-clay complex, yielding a formulation of up to 40% active ingredient, and 1.6-fold reduction in herbicide release in comparison to the commercial formulation. Hence, the PC-montmorillonite complex can form a basis for environmentally friendly formulations of herbicides, which would yield reduced leaching.We acknowledge financial support by the Spanish Ministry of Education and Science (Project AGL2005-00164) and Junta de Andalucía (Project P06-FQM-1909).Peer reviewe

Reduced metribuzin pollution with phosphatidylchline clay formulations

8 pages, 5 tables, 6 figures, 40 references.BACKGROUND: Metribuzin is a widely used herbicide that has been identified as a groundwater contaminant. In this study, slow-release formulations of metribuzin were designed by encapsulating the active ingredient in phosphatidylcholine (PC) vesicles and adsorbing the vesicles ontomontmorillonite. RESULTS:Themaximumactive ingredient content intheslow-release formulationswas246g kg−1. Infrared spectroscopy results revealed that the hydrophobic interactions between metribuzin and the alkyl chains on PCwere necessary for encapsulation. In addition,water bridges connecting the herbicide and the PC headgroup enhanced the solubility ofmetribuzin in PC. Adsorption experiments in soils were performed to evaluate the relationship between sorption and leaching. Funnel experiments in a sandy soil revealed that the herbicide was not irreversibly retained in the formulation matrix. In soil column experiments, PC–clay formulations enhanced herbicide accumulation and biological activity in the top soil layer relative to a commercial formulation. PC–clay formulations also reduced the dissipation of metribuzin by a factor of 1.6–2.5. CONCLUSIONS: A reduction in the recommended dose of metribuzin can be achieved by employing PC–clay formulations, which reduces the environmental risk associated with herbicide applications.Moreover, PC andmontmorillonite are non-toxic and do not negatively affect the environment.This research was supported by the MEC Project CTM2009-07425 and Junta de Andalucía Project P09-RNM4581. Both projects received funding by the European Social Fund.Peer reviewe

A clay-vesicle system for water purification from organic pollutans

9 pages, 7 tables, 3 figures, 31 references.Vesicle-clay complexes in which positively charged vesicles composed of didodecyldimethylammonium (DDAB) were adsorbed on montmorillonite removed efficiently anionic (sulfentrazone, imazaquin) and neutral (alachlor, atrazine) pollutants from water. These complexes (0.5% w:w) removed 92-100% of sulfentrazone,imazaquin and alachlor and 60% of atrazine from a solution containing 10 mg/L. A synergistic effect on the adsorption of atrazine was observed when all pollutants were present simultaneously (30 mg/L each), its percentage of removal being 85.5. Column filters (18 cm) filled with a mixture of quartz sand and vesicle-clay (100:1, w:w) were tested. For the passage of 1 L (25 pore volumes) of a solution including all the 11 pollutants at 10 mg/L each, removal was complete for sulfentrazone and imazaquin, 12 94% for alachlor and 53.1% for atrazine, whereas removal was significantly less efficient when using activated carbon. A similar advantage of the vesicle-clay filter was observed for the capacities of removal.The authors acknowledge financial support by the Spanish Ministry of Education and Science (Projects AGL2005-00164 and CTM2006-04626/TECNO).Peer reviewe

Environmentally-friendly formulations of alachlor and atrazine: preparation, characterization and reduced leaching

8 pages, 5 figures, 1 table, 36 references.Atrazine and alachlor formulations were designed by encapsulating the herbicide molecules into phosphatidylcholine (PC) vesicles, which subsequently were adsorbed on montmorillonite. PC and montmorillonite are classified as substances of minimal toxicological risk by the U.S. EPA. PC enhanced alachlor and atrazine solubilities by 15- and 18-fold, respectively. A 6 mM PC:5 g/L clay ratio was found as optimal for PC adsorption on the clay. Active ingredient contents of the PC-clay formulations ranged up to 8.6% for atrazine and 39.5% for alachlor. Infrared spectroscopy showed hydrophobic interactions of herbicide molecules with the alkyl chains of PC, in addition to hydrophilic interactions with the PC headgroup. Release experiments in a sandy soil showed a slower rate from the PC-clay formulations than the commercial ones. Soil column experiments under moderate irrigation and bioactivity experiments indicate that a reduction in the recommended dose of alachlor and atrazine can be accomplished by using PC-clay formulations.The authors acknowledge financial support by the Spanish Ministry of Education and Science (Project AGL2005-00164) and Junta de Andalucía (Project P06-FQM-1909).Peer reviewe