Effects of the herbicides prosulfuron and metolachlor on fluxes of CO₂, N₂O, and CH₄ in a fertilized Colorado grassland soil

Abstract

[1] The effect that pesticides have on trace gas production and consumption in agricultural soils is often overlooked. Independent field and laboratory experiments were used to measure the effects that the commonly used herbicides prosulfuron and metolachlor have on trace gas fluxes (CO 2 , N 2 O, and CH 4 ) from fertilized soil of the Colorado shortgrass steppe. Separate sample plots (1 m 2 ) on tilled and no-till soil at the sites included the following treatments: 1) a control without fertilizer or herbicide, 2) a fertilized (NH 4 NO 3 equivalent to 244 kg ha À1 ) control without herbicide, 3) and fertilized plots amended with an herbicide (prosulfuron equivalent to 0.46 kg ha À1 57% by weight active ingredient or metolachlor equivalent to 5.7 L ha À1 , 82.4% by weight active ingredient). During an initial study of one year duration, measurement of gas exchange revealed that prosulfuron-amendment stimulated N 2 O emissions and CH 4 consumption by as much as 1600% and 1300% during a single measurement, respectively. During a second set of flux measurements beginning in August 2001, more frequent weekly measurements were made during a twelve week period. From this second study an increased N 2 O efflux and CH 4 uptake occurred after a 7-week lag period that persisted for about 5 weeks. These changes in gas flux amounted to an overall increase of 41% and 30% for N 2 O emission and CH 4 consumption, respectively. The co-occurrence of stimulated N 2 O and CH 4 fluxes suggests a similar cause that is related to prosulfuron degradation. Evidence suggested that prosulfuron degradation stimulated microbial activity responsible for trace gas flux. Ultimately, prosulfuron-amendment led to an $50% reduction in the global warming potential from N 2 O and CH 4 fluxes at this field site, which is equivalent to a reduction of the global warming potential of 0.18 mols CO 2 m À2 d À1 from these gases. Metolachlor application did not significantly affect the trace gas fluxes measured. These results demonstrate the potential impact that pesticides have on trace gas fluxes from agricultural soils, which could mean that the effects of other agricultural practices have been over or under estimated.

Herbicide applications increase greenhouse gas emissions of alfalfa pasture in the inland arid region of northwest China

“…Our field study demonstrated that CH 4 uptake was enhanced following the application of QE and BT (Figs. 3A and 3B), which is similar to the increase in CH 4 uptake as a result of the application of Prosulfuron observed by Kinney et al (2004b). Soil treated by herbicides maintained a relatively higher oxidation-reduction potential than those of the CK, which resulted in smaller CH 4 fluxes following the application of QE and BT and increased CH 4 uptake by pasture soil.…”

Application of herbicides is likely to reduce greenhouse gas (N2O and CH4) emissions from rice–wheat cropping systems

“…Moreover, even at very low concentrations, butachlor inhibited CH 4 production and oxidation (Mohanty et al, 2001(Mohanty et al, , 2004. Another study demonstrated that prosulfuron stimulated N 2 O emissions and CH 4 consumption in a fertilized Colorado grassland soil by as much as 1600% and 1300%, respectively (Kinney et al, 2004). Das et al (2011) also demonstrated that separate applications of the herbicides bensulfuronmethyl and pretilachlor resulted in lower N 2 O and CH 4 emissions from a flooded rice field.…”

Estudo de fluxo de óxido nitroso (N2O) regional na Bacia Amazônica

“…O processo de nitrificação é um processo aeróbio porque as bactérias nitrificadoras utilizam a enzima amônia monoxigenase a qual requer moléculas de O 2 para oxidar o íon amônio. Tanto o N 2 O como o NO são produzidos neste processo (Brasseur et al, 1999;Kinney et al, 2004) (Granier et al, 2004).…”

“…A desnitrificação é a redução anaeróbica do íon nitrato a nitrogênio diatômico pelas bactérias desnitrificantes como as Pseudomonas denitrificans, as quais, em ambientes com restrição de oxigênio disponível, com quantidades suficientes de redutor adequado, como o carbono orgânico, e de compostos nitrogenados (Kinney et al, 2004;Brasseur et al, 1999), e grande quantidade de água (Marcelino, 2009) (3.6)…”