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Chilean Journal of Agricultural Research
Instituto de Investigaciones Agropecuarias, INIA
ISSN: 0718-5820
EISSN: 0718-5839
Vol. 68, No. 1, 2008, pp. 13-20
Bioline Code: cj08002
Full paper language: English
Document type: Research Article
Document available free of charge

Chilean Journal of Agricultural Research, Vol. 68, No. 1, 2008, pp. 13-20

 en Glyphosate Mineralization: Effect of Temperature and Soybean and Corn Crop Residues
Rampoldi, Ariel; Hang, Susana & Barriuso, Enrique

Abstract

Mineralization is the main mechanism of dissipation of glyphosate herbicide (N-[phosphonomethyl] glycine) in soil. However, there is scarce information about the mineralization process in strata formed by stubbles in no-tillage systems. The kinetics and rate of mineralization of herbicide in stubbles of soybean ( Glycine max L. Merr. check for this species in other resources ) and corn ( Zea mays L. check for this species in other resources ) were investigated. To evaluate the effect of age of crop residues, samples of soybean stubbles were collected immediately after harvest (Soja 1) and four months after harvest (Soja 2). Corn crop residues were collected three months after harvest. Glyphosate evolution and total microbial activity (TMA) were monitored by release of 14C-CO2 and C-CO2 under laboratory conditions with two temperatures, 15 and 28 ºC. Crop residues size was evaluated using grinding (1 mm) and cut (1 to 2 cm) stubbles. Results showed that glyphosate mineralization was affected by the incubation temperature and the origin and age of crop residues. Size of crop residues did not modify glyphosate mineralization. Average glyphosate mineralization after 56 days of incubation at 15 and 28 ºC was of 3.9 and 9.9%, respectively, of the 14C-glyphosate initially applied. In maize crop residues the percentages were 2.0 and 3.0%, respectively, at 15 and 28 ºC. A similar evolution was detected for TMA. The co-metabolic nature of glyphosate mineralization was corroborated. An inverse relation between C/N ratio and glyphosate mineralization was detected. Higher glyphosate mineralization was detected in fresh soybean stubbles, suggesting that applications on aged crop residues could increase the persistence of glyphosate in no-tillage systems.

Keywords
glyphosate, stubbles, mineralization, non-tillage system, total microbial activity.

 
 es Mineralización de Glifosato: Efecto de la Temperatura y los Residuos Vegetales de Soya y Maíz
Rampoldi, Ariel; Hang, Susana & Barriuso, Enrique

Resumen

La mineralización es el principal mecanismo de disipación del herbicida glifosato (N-[fosfonometil] glicina) en el suelo. Existe escasa información sobre el proceso de mineralización de glifosato en el estrato formado por rastrojos en suelos cultivados en sistema de siembra directa. Las muestras de rastrojos de soja ( Glycine max L. Merr. check for this species in other resources ) se obtuvieron inmediatamente después de la cosecha (Soja 1) y cuatro meses después de la cosecha (Soja 2) y las de maíz ( Zea mays L. check for this species in other resources ) a los tres meses de su cosecha (Maíz). La evolución de 14C-glifosato y de la actividad microbiana total (TMA) fue monitoreada por liberación de 14C-CO2 y C-CO2 en condiciones de laboratorio, a dos temperaturas, 15 y 28 ºC. El efecto del tamaño de los residuos de cosecha fue evaluado en rastrojo molido (1 mm) y cortado (1 a 2 cm). A los 56 días de incubación del rastrojo de soja se mineralizó 3.9 y 9.9% del 14C-glifosato inicial aplicado a 15 y 28 ºC, respectivamente, mientras que en los rastrojos de maíz la mineralización fue de 2.0 y 3.0%. Se confirmó la naturaleza cometabólica de la mineralización de glifosato. Se detectó una relación inversa entre la relación C/N y el porcentaje de 14C-CO2 liberado. Sobre residuos frescos, con mayor TMA, incrementó la mineralización de glifosato. Aplicaciones de glifosato sobre rastrojos más viejos podrían incrementar la persistencia del herbicida en sistemas de siembra directa.

Palabras-clave
glifosato, rastrojo, mineralización, siembra directa, actividad microbiana total.

 
© Copyright 2008 - Instituto de Investigaciones Agropecuarias, INIA (Chile).
Alternative site location: http://www.inia.cl

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