Efecto de la quema prescripta de un pastizal sobre el balance de CO2

El objetivo fue evaluar el efecto de la quema prescripta de un pastizal con predominio de ramíneas sobre la emisión y captura de CO2. El sitio no recibió quema por 25 años. Los tratamientos fueron: T1 = sin quema; T2 = quema anual y T3 = quema bianual. Se tomaron muestras de la biomasa aérea viva y muerta. Después de los eventos de quema se colectaron las cenizas. El contenido promedio de C del material vegetal fue del 45 %. La cantidad de CO2 liberado en promedio en forma anual para los eventos de quema fueron: 10.199 y 5.152 kg ha-1 respectivamente para T2 y T3. En T1 se encontró una tendencia creciente en el contenido de carbono almacenado en la biomasa aérea viva y muerta, se consideró en equilibrio la emisión y la captura de CO2. En la quema anual se capturó 12.401 kg de CO2 ha-1, la diferencia entre lo capturado y lo emitido fue de 2.202 kg de CO2 ha-1. En la quema bianual se capturó 7.904 kg de CO2 en forma anual y por la quema se liberó 5.152 kg ha-1, la diferencia entre lo capturado y lo emitido es de 2.752 kg de CO2. El CO2 liberado durante la quema es rápidamente capturado a través del proceso de fotosíntesis en el siguiente período de crecimiento vegetal. La captura de CO2 en los tratamientos que recibieron quema fue mayor a la emisión de CO2 durante el proceso de combustión de la biomasa

Enteric methane mitigation strategies for ruminant livestock systems in the Latin America and Caribbean region: a meta-analysis.

Latin America and Caribbean (LAC) is a developing region characterized for its importance for global food security, producing 23 and 11% of the global beef and milk production, respectively. The region?s ruminant livestock sector however, is under scrutiny on environmental grounds due to its large contribution to enteric methane (CH4) emissions and influence on global climate change. Thus, the identification of effective CH4 mitigation strategies which do not compromise animal performance is urgently needed, especially in context of the Sustainable Development Goals (SDG) defined in the Paris Agreement of the United Nations. Therefore, the objectives of the current study were to: 1) collate a database of individual sheep, beef and dairy cattle records from enteric CH4 emission studies conducted in the LAC region, and 2) perform a meta-analysis to identify feasible enteric CH4 mitigation strategies, which do not compromise animal performance. After outlier?s removal, 2745 animal records (65% of the original data) from 103 studies were retained (from 2011 to 2021) in the LAC database. Potential mitigation strategies were classified into three main categories (i.e., animal breeding, dietary, and rumen manipulation) and up to three subcategories, totaling 34 evaluated strategies. A random effects model weighted by inverse variance was used (Comprehensive Meta-Analysis V3.3.070). Six strategies decreased at least one enteric CH4 metric and simultaneously increased milk yield (MY; dairy cattle) or average daily gain (ADG; beef cattle and sheep). The breed composition F1 Holstein × Gyr decreased CH4 emission per MY (CH4IMilk) while increasing MY by 99%. Adequate strategies of grazing management under continuous and rotational stocking decreased CH4 emission per ADG (CH4IGain) by 22 and 35%, while increasing ADG by 22 and 71%, respectively. Increased dietary protein concentration, and increased concentrate level through cottonseed meal inclusion, decreased CH4IMilk and CH4IGain by 10 and 20% and increased MY and ADG by 12 and 31%, respectively. Lastly, increased feeding level decreased CH4IGain by 37%, while increasing ADG by 171%. The identified effective mitigation strategies can be adopted by livestock producers according to their specific needs and aid LAC countries in achieving SDG as defined in the Paris Agreement

Imidacloprid and pyrimethanil soil sorption

The sorption of imidacloprid and pyrimethanil was measured in different soils of southern Europe. Pyrimethanil sorption (Kf=1.2-4.60) was higher than that of imidacloprid (Kf=0.31-1.99). Sorption was influenced by organic carbon content and increased with time when the soil was incubated at 25 $^\circ$C and 35% soil water content. Over a period of 14 days, the distribution coefficient between solid (soil) and solution phases increased by orders of magnitude of 2 and 4 respectively, for imidacloprid and pyrimethanil. The increment is consistent with the degradation rate measured, supporting the hypothesis of the two sites of sorption. Care should be taken when such values are used to predict pesticide fate in soil, particularly for regulatory purposes during pesticide registration.Sorption de l'imidacloprid et du pyriméthanil dans le sol. La sorption de l'imidacloprid et du pyriméthanil a été mesurée dans divers sols d'Europe méridionale. La sorption du pyriméthanil (Kf = 1,2-4,60) était plus élevée que celle de l'imidacloprid (Kf = 0,31-1,99). Elle est influencée par la teneur en carbone organique et augmente avec le temps lorsque le sol est incubé à 25 $^\circ$C et que sa teneur en eau est de 35 % . Sur une période de 14 jours, le coefficient de répartition entre la phase solide du sol et la phase liquide (solution) augmente d'un ordre de grandeur de 2 et 4 respectivement pour l'imidacloprid et le pyriméthanil. L'accroissement est en accord avec le taux de dégradation mesuré, ce qui confirme l'hypothèse de deux lieux de sorption. Il faut faire attention lorsqu'on utilise de telles valeurs pour prédire le devenir du pesticide dans le sol, en particulier dans des buts de réglementation au cours de la procédure d'enregistrement du pesticide

Lignin and ethylcellulose in controlled release formulations to reduce leaching of chloridazon and metribuzin in light-textured soils

8 páginas.-- 5 figuras.-- 2 tablas.-- 34 referencias.--In this research, controlled release formulations (CRFs) of the herbicides chloridazon and metribuzin, identified as potential leachers, have been evaluated in soils with different texture. To prepare the CRFs, ethylcellulose (EC) and dibutylsebacate (DBS) have been used as coating agents in lignin-polyethylene glycol based formulations. Mobility experiments have been carried out in two light textured soils (sandy and sandy-loam). Breakthrough curves have shown that the use of CRFs reduces the presence of chloridazon and metribuzin in the leachate compared to technical and commercial products, being the lignin CRF coated with EC and DBS the most efficient to diminish the herbicide leaching. Mass balance study has shown a higher amount of chloridazon and metribuzin recovered in soils when these herbicides were tested as CRFs compared to technical and commercial products. The gradual release of herbicides from the CRFs resulting in a rather available levels of chloridazon and metribuzin in soil for a longer time. A good correlation between percentages of herbicide recovered in leachates and T50 values (time corresponding to 50% release of herbicide in water) was obtained, which allows to select the most appropriate CRF in each agro-environmental practice to reduce the potential pollution of groundwater by chloridazon and metribuzin.This work was supported by the Ministerio de Economía y Competitividad, Spain, Project AGL2010-18286, and Junta de Andalucía Excellence Project P-06-FQM-1909, both co-financed by FEDER.Peer reviewe