• Energy Research
• 2016-2025close

Les rizières sont l'un des plus grands facilitateurs des gaz à effet de serre (GES) qui sont principalement régulés par la fertilisation à l'azote (N). L'optimisation des utilisations de l'azote basée sur le rendement a été tentée depuis longtemps, cependant, l'amélioration des technologies de pointe et la rigidité du réchauffement climatique doivent réajuster le taux d'azote. Cependant, peu d'études individuelles ont commencé, tentant ici de généraliser le taux d'azote optimal qui minimise le potentiel de réchauffement planétaire (PRG) et fournit simultanément un rendement suffisant dans le système rizicole. Pour satisfaire la demande alimentaire croissante avec des terres inadéquates et un impact environnemental moindre, les émissions de GES sont de plus en plus évaluées en fonction du rendement. Cette revue systématique (20 études publiées comprenant 21 sites d'étude et 190 observations) visait à tester l'hypothèse selon laquelle le PRG le plus faible à l'échelle du rendement fournirait le PRG minimum des émissions de CH4 et de N2O du système rizicole à des rendements presque optimaux. Les résultats ont révélé qu'il existait une forte relation quadratique polynomiale entre les émissions de CH4 et le taux d'azote et une forte corrélation positive entre les émissions de N2O et le taux d'azote. Par rapport au contrôle, la faible dose d'azote émettait moins (23 %) de CH4 alors que la forte dose d'azote émettait plus (63 %) d'émissions de CH4. L'émission de N2O la plus élevée observée à un niveau modéré d'azote. Au total, environ 96 % et 4 % des GES ont été émis sous forme de CH4 et de N2O, respectivement. Le PRG moyen des émissions de CH4 et de N2O du riz était de 5758 kg éq CO2 ha−1. Le PRG le moins élevé à l'échelle du rendement (0,7565 (kg éq. CO2 ha−1)) a été enregistré à 190 kg N ha−1, ce qui a fourni le rendement presque maximal. Cette dose pourrait être une dose appropriée dans les systèmes rizicoles gérés par drainage de mi-saison, en particulier dans les conditions climatiques tropicales et subtropicales. Ce PRG à l'échelle du rendement soutient le concept de gagnant-gagnant pour la sécurité alimentaire et les aspects environnementaux en équilibrant entre une productivité rizicole viable et le maintien de gaz à effet de serre convaincants. Los arrozales son uno de los mayores facilitadores de gases de efecto invernadero (GEI) que están regulados predominantemente por la fertilización con nitrógeno (N). La optimización de los usos de N en función del rendimiento se ha intentado desde hace mucho tiempo, sin embargo, la mejora de las tecnologías de vanguardia y la rigidez del calentamiento global necesitan reajustar la tasa de N. Aunque pocos estudios individuales comenzaron a hacerlo, en este documento se intentó como una revisión sistemática para generalizar la tasa óptima de N que minimiza el potencial de calentamiento global (GWP) al mismo tiempo que proporciona un rendimiento suficiente en el sistema de arroz. Para satisfacer la creciente demanda de alimentos con tierras inadecuadas y menos impacto ambiental, las emisiones de GEI se evalúan cada vez más a escala de rendimiento. Esta revisión sistemática (20 estudios publicados que consisten en 21 sitios de estudio y 190 observaciones) tuvo como objetivo probar la hipótesis de que el GWP a escala de rendimiento más bajo proporcionaría el GWP mínimo de emisiones de CH4 y N2O del sistema de arroz a rendimientos casi óptimos. Los resultados revelaron que había una fuerte relación cuadrática polinómica entre las emisiones de CH4 y la tasa de N y una fuerte correlación positiva entre las emisiones de N2O y la tasa de N. En comparación con el control, la dosis baja de N emitió menos (23%) de CH4, mientras que la dosis alta de N emitió más (63%) de CH4. La mayor emisión de N2O observada a nivel de N moderado. En GWP total, alrededor del 96% y 4%, los GEI se emitieron como CH4 y N2O, respectivamente. El GWP medio de las emisiones de CH4 y N2O del arroz fue de 5758 kg de CO2 eq ha−1. El GWP a escala de menor rendimiento (0.7565 (kg CO2 eq. ha−1)) se registró a 190 kg N ha−1 que proporcionó el rendimiento más cercano. Esta dosis podría ser una dosis adecuada en sistemas de arroz gestionados por drenaje a mitad de temporada, especialmente en condiciones climáticas tropicales y subtropicales. Este PCA a escala de rendimiento respalda el concepto de ganar-ganar para la seguridad alimentaria y los aspectos ambientales a través del equilibrio entre la productividad viable del arroz y el mantenimiento de gases de efecto invernadero convincentes. حقول الأرز هي واحدة من أكبر ميسرات غازات الدفيئة (GHGs) التي يتم تنظيمها في الغالب عن طريق التسميد بالنيتروجين (N). ومع ذلك، فقد تم تجربة تحسين استخدامات N بناءً على العائد منذ فترة طويلة، ومع ذلك، فإن تحسين أحدث التقنيات وصلابة الاحترار العالمي يحتاج إلى إعادة ضبط معدل N. على الرغم من أن عددًا قليلاً من الدراسات الفردية قد بدأت، إلا أن المحاولة هنا كمراجعة منهجية لتعميم معدل N الأمثل الذي يقلل من إمكانات الاحترار العالمي (GWP) توفر في الوقت نفسه غلة كافية في نظام الأرز. لتلبية الطلب المتزايد على الغذاء مع عدم كفاية الأراضي وتأثير أقل على البيئة، يتم تقييم انبعاثات غازات الدفيئة بشكل متزايد كأساس لقياس الغلة. تهدف هذه المراجعة المنهجية (20 دراسة منشورة تتكون من 21 موقع دراسة و 190 ملاحظة) إلى اختبار الفرضية القائلة بأن أدنى قدرة على إحداث الاحترار العالمي على نطاق الغلة ستوفر الحد الأدنى من القدرة على إحداث الاحترار العالمي لانبعاثات الميثان وأكسيد النيتروز من نظام الأرز عند غلة شبه مثالية. وكشفت النتائج عن وجود علاقة تربيعية قوية متعددة الحدود بين انبعاثات الميثان ومعدل النيتروجين وارتباط إيجابي قوي بين انبعاثات أكسيد النيتروجين ومعدل النيتروجين. مقارنة بالتحكم في جرعة N المنخفضة المنبعثة أقل (23 ٪) من الميثان في حين أن جرعة N العالية تنبعث منها انبعاثات أعلى (63 ٪) من الميثان. أعلى انبعاثات أكسيد النيتروز لوحظت عند مستوى N معتدل. في إجمالي قدرة الاحترار العالمي، حوالي 96 ٪ و 4 ٪، انبعثت غازات الدفيئة في صورة الميثان وأكسيد النيتروز، على التوالي. كان متوسط احتمالية الاحترار العالمي لانبعاثات الميثان وأكسيد النيتروز من الأرز 5758 كجم من مكافئ ثاني أكسيد الكربون للهكتار-1. تم تسجيل أقل قدرة احترار عالمي مقاسة (0.7565 (كجم من مكافئ ثاني أكسيد الكربون هكتار-1)) عند 190 كجم نيوتن هكتار-1 والتي وفرت أقصى عائد تقريبًا. يمكن أن تكون هذه الجرعة جرعة مناسبة في أنظمة الأرز المدارة لتصريف منتصف الموسم خاصة في الظروف المناخية الاستوائية وشبه الاستوائية. تدعم هذه القدرة على إحداث الاحترار العالمي المحسوبة بالعائد مفهوم الفوز المشترك للأمن الغذائي والجوانب البيئية من خلال الموازنة بين إنتاجية الأرز القابلة للحياة والحفاظ على غازات الدفيئة المقنعة. Rice paddies are one of the largest greenhouse gases (GHGs) facilitators that are predominantly regulated by nitrogen (N) fertilization. Optimization of N uses based on the yield has been tried a long since, however, the improvement of the state-of-the-art technologies and the stiffness of global warming need to readjust N rate. Albeit, few individual studies started to, herein attempted as a systematic review to generalize the optimal N rate that minimizes global warming potential (GWP) concurrently provides sufficient yield in the rice system. To satisfy mounted food demand with inadequate land & less environmental impact, GHGs emissions are increasingly evaluated as yield-scaled basis. This systematic review (20 published studies consisting of 21 study sites and 190 observations) aimed to test the hypothesis that the lowest yield-scaled GWP would provide the minimum GWP of CH4 and N2O emissions from rice system at near optimal yields. Results revealed that there was a strong polynomial quadratic relationship between CH4 emissions and N rate and strong positive correlation between N2O emissions and N rate. Compared to control the low N dose emitted less (23%) CH4 whereas high N dose emitted higher (63%) CH4 emission. The highest N2O emission observed at moderated N level. In total GWP, about 96% and 4%, GHG was emitted as CH4 and N2O, respectively. The mean GWP of CH4 and N2O emissions from rice was 5758 kg CO2 eq ha−1. The least yield-scaled GWP (0.7565 (kg CO2 eq. ha−1)) was recorded at 190 kg N ha−1 that provided the near utmost yield. This dose could be a suitable dose in midseason drainage managed rice systems especially in tropical and subtropical climatic conditions. This yield-scaled GWP supports the concept of win–win for food security and environmental aspects through balancing between viable rice productivity and maintaining convincing greenhouse gases.

The effective utilization of slag fertilizer in agriculture to neutralize soil acidity, improve crop productivity, mitigate greenhouse gas emissions, and stabilize heavy metals in contaminated soils turns it into a high value added product in sustainable agriculture. These effects could be due to the shift in microbial metabolism and/or modification of microbial habitats. At the system level, soil microorganisms play an integral role in virtually all ecosystem processes. There is a growing interest to reveal the underlying mechanisms of slag-microbe interactions and the contribution of soil biota to ecosystem functioning. In this perspective, we discuss the possible driving mechanisms of slag-microbe interactions in soil and how these slag-microbe interactions can affect crop yield, greenhouse gas emissions, soil carbon sequestration, and heavy metal stabilization in contaminated soils. In addition, we discuss the problems and environmental concerns in using slag in agriculture. Emphasis has been given for further research to validate the proposed mechanisms associated with slag-microbe interactions for increasing soil quality, crop productivity, and mitigating environmental consequences. While evaluating the slag amendment, effects on agriculture and environment, the potential risks, socio-economics, techno-economics, and ethics should be assessed.

Monolayer barriers, which are usually known as evapotranspiration (ET) covers, have long been used as alternative final cover systems in waste landfills. Coal bottom ash was evaluated as a good alternative to soil in landfill ET cover systems to increase the bottom ash (BA) recycling ratio in the past. In a previous study, applying BA promoted plant growth characteristics and improved the soil physicochemical properties, particularly the soil organic carbon (SOC) content. In this study, we investigated the effect of BA on the SOC increase by examining the chemical and physical characteristics of ET cover systems, and we compared BA mixed and pure soils. We collected two types of soil from the landfill cover, namely, BA mixed soil (BA 35% + soil 65%) and soil alone (100%), for treatments during the 5th year after installation. Bottom ash mixed soil has four times more SOC than the pure soil at the surface soil layer, but the SOC contents significantly decreased with the soil depth in BA mixed soil, and no differences were found between BA mixed soil and pure soil below a 25 cm soil depth. In addition, there was no significant difference in the chemical composition of the SOC according to a13C NMR. However, the allophane contents were significantly higher in BA mixed soil than pure soil, which physically protects the material from organic matter decomposition. Conclusively, the higher allophane content originating from BA might act as the primary factor in the high accumulation of soil organic carbon in the BA mixed soil layer by retarding the organic matter decomposition.

Plastic film mulching (FM) became a general practice to enhance crop productivity and its net primary production (NPP), but it can increase greenhouse gas (GHG) emissions. The proper addition of organic amendments might effectively decrease the impact of FM on global warming. To evaluate the feasibility of biomass addition on decreasing this negative influence, cover crop biomass as a green manure was incorporated with different recycling levels (0-100% of aboveground biomass) under FM and no-mulching. The net global warming potential (GWP) which integrated with soil C stock change and GHG (N2O and CH4) fluxes with CO2-equivalent was evaluated during maize cultivation. Under the same biomass incorporation, FM significantly enhanced the grain productivity and NPP of maize by 22-61 and 18-58% over no-mulching, respectively. In contrast, FM also highly increased the respired C loss, which was 11-95% higher than NPP increase, over no-mulching. Irrespective with biomass recycling ratio and mulching system, negative NECB which indicates the decrease of soil C stock was observed, mainly due to big harvest removal. FM decreased more soil C stock by 57-158% over no-mulching, but its C stock was clearly increased with increasing biomass addition. FM significantly increased total N2O and CH4 fluxes by 4-61 and 140-600% over no-mulching, respectively. Soil C stock changes mainly decided net GWP scale, but N2O and CH4 fluxes negligibly influenced. As a result, FM highly increased net GWP over no-mulching, while this net GWP was clearly decreased with increasing biomass application. However, cover cropping, and its biomass recycling was not enough to compensate the negative impact of FM on global warming. Therefore, more biomass incorporation might be essential to compensate this negative effect of FM.

Abstract Oil palm (OP) plantations are gradually replacing tropical rainforest in Malaysia, one of the largest palm oil producers globally. Conversion of lands to OP plantations has been associated with compositional shifts of the microbial community, with consequences on the greenhouse gas (GHG) emissions. While the impact of the change in land use has recently been investigated for microorganisms involved in N2O emission, the response of the aerobic methanotrophs to OP agriculture remains to be determined. Here, we monitored the bacterial community composition, focusing on the aerobic methanotrophs, in OP agricultural soils since 2012, 2006, and 1993, as well as in a tropical rainforest, in 2019 and 2020. High-affinity methane uptake was confirmed, showing significantly lower rates in the OP plantations than in the tropical rainforest, but values increased with continuous OP agriculture. The bacterial, including the methanotrophic community composition, was modified with ongoing OP agriculture. The methanotrophic community composition was predominantly composed of unclassified methanotrophs, with the canonical (Methylocystis) and putative methanotrophs thought to catalyze high-affinity methane oxidation present at higher relative abundance in the oldest OP plantation. Results suggest that the methanotrophic community was relatively more stable within each site, exhibiting less temporal variations than the total bacterial community. Uncharacteristically, a 16S rRNA gene-based co-occurrence network analysis revealed a more complex and connected community in the OP agricultural soil, which may influence the resilience of the bacterial community to disturbances. Overall, we provide a first insight into the ecology and role of the aerobic methanotrophs as a methane sink in OP agricultural soils.

[No abstract available]

In rice paddy, the closed chamber method is broadly used to estimate methane (CH4) emission rate. Since rice plants can significantly affect CH4 production, oxidation and emission, rice plantation inside the chamber is standardized in IPCC guidelines. Methane emission rate is calculated using the increased concentration inside the headspace. Biomass growth might decrease the headspace volume, and thus CH4 emission rates might be overestimated. To evaluate the influence of chamber headspace decreased by rice plant development on CH4 emission rates, five Korean rice cultivars were cultivated in a typical rice paddy, and physical volume changes in rice biomass were assayed using water displacement method. The recommended acrylic closed chambers (H. 1.2 m x W. 0.6 m x L. 0.6 m) were installed, and eight rice plants were transplanted inside the chamber with the same space interval with the outside. Biomass growth significantly decreased the headspace volume of the chamber. However, this volume covered only 0.48–0.55% of the closed chamber volume at the maximum growth stage. During the whole cropping period, mean 0.24–0.28% of chamber headspace was allocated by plant biomass, and thus this level of total CH4 emissions was overestimated. However, this overestimation was much smaller than the errors coming from other investigation processes (i.e., chamber closing hour, temperature recording, inconstant flooding level, different soil environments, etc.) and rice physiological changes. In conclusion, the influence of physical biomass volume inside the closed chamber was negligible to make the error in total CH4 emission assessment in rice paddies.