• Energy Research

Reducing methane (CH4) emission from paddy rice production is an important target for many Asian countries in order to comply with their climate policy commitments. National greenhouse gas (GHG) inventory approaches like the Tier-2 approach of the Intergovernmental Panel on Climate Change (IPCC) are useful to assess country-scale emissions from the agricultural sector. In paddy rice, alternate wetting and drying (AWD) is a promising and well-studied water management technique which, as shown in experimental studies, can effectively reduce CH4 emissions. However, so far little is known about GHG emission rates under AWD when the technique is fully controlled by farmers. This study assesses CH4 and nitrous oxide (N2O) fluxes under continuous flooded (CF) and AWD treatments for seven subsequent seasons on farmers’ fields in a pumped irrigation system in Central Luzon, Philippines. Under AWD management, CH4 emissions were substantially reduced (73% in dry season (DS), 21% in wet season (WS)). In all treatments, CH4 is the major contributor to the total GHG emission and is, thus, identified as the driving force to the global warming potential (GWP). The contribution of N2O emissions to the GWP was higher in CF than in AWD, however, these only offset 15% of the decrease in CH4 emission and, therefore, did not jeopardize the strong reduction in the GWP. The study proves the feasibility of AWD under farmers’ management as well as the intended mitigation effect. Resulting from this study, it is recommended to incentivize dissemination strategies in order to improve the effectiveness of mitigation initiatives. A comparison of single CH4 emissions to calculated emissions with the IPCC Tier-2 inventory approach identified that, although averaged values showed a sufficient degree of accuracy, fluctuations for single measurement points have high variation which limit the use of the method for field-level assessments.

Le riz de plaine est une source importante d'émissions anthropiques de gaz à effet de serre (GHGE) et la principale source d'émissions agricoles pour de nombreux pays en développement d'Asie. Dans le même temps, les sols de riz représentent l'un des plus grands puits de carbone organique du sol mondial. La gestion de la paille est un facteur clé dans le contrôle des émissions et du potentiel d'atténuation du riz, principalement en affectant le méthane (CH4) provenant de la décomposition anaérobie et les pertes de carbone dues à la combustion. Cependant, il est difficile de parvenir à une gestion intelligente du riz face au climat tout en améliorant les rendements et les bénéfices agricoles en raison des compromis économiques et environnementaux. Cet équilibre pourrait être atteint avec des pratiques appropriées spécifiques au site. Ce chapitre traite de ces pratiques de gestion de la paille qui affectent les GHGE à l'échelle du rendement et les options d'atténuation dans différents environnements rizicoles. El arroz de tierras bajas es una fuente importante de emisiones antropogénicas de gases de efecto invernadero (GEI) y la principal fuente de emisiones agrícolas para muchos países en desarrollo de Asia. Al mismo tiempo, los suelos de arroz representan uno de los mayores sumideros mundiales de carbono orgánico del suelo. El manejo de la paja es un factor clave para controlar las emisiones y el potencial de mitigación del arroz, principalmente al afectar el metano (CH4) de la descomposición anaeróbica y las pérdidas de carbono por la quema. Sin embargo, lograr una gestión climáticamente inteligente del arroz y al mismo tiempo mejorar los rendimientos y las ganancias agrícolas es un desafío debido a las compensaciones económico-ambientales. Este equilibrio podría cumplirse con prácticas apropiadas específicas del sitio. Este capítulo analiza estas prácticas de manejo de la paja que afectan los GEI a escala de rendimiento y las opciones de mitigación en diferentes entornos de arroz. Lowland rice is a significant source of anthropogenic greenhouse gas emissions (GHGEs) and the primary source of agricultural emissions for many developing countries in Asia. At the same time, rice soils represent one of the largest global soil organic carbon sinks. Straw management is a key factor in controlling the emissions and mitigation potential of rice primarily by affecting methane (CH4) from anaerobic decomposition and carbon losses from burning. Achieving climate-smart management of rice while also improving yields and farm profits, however, is challenging due to economic-environmental trade-offs. This balance could be met with appropriate site-specific practices. This chapter discusses these straw management practices that affect yield-scaled GHGEs and mitigation options in different rice environments. يعد الأرز في الأراضي المنخفضة مصدرًا مهمًا لانبعاثات غازات الدفيئة البشرية المنشأ (GHGEs) والمصدر الرئيسي للانبعاثات الزراعية للعديد من البلدان النامية في آسيا. وفي الوقت نفسه، تمثل تربة الأرز واحدة من أكبر المصارف العالمية للكربون العضوي في التربة. تعد إدارة القش عاملاً رئيسياً في التحكم في الانبعاثات وإمكانات التخفيف من الأرز في المقام الأول عن طريق التأثير على الميثان (CH4) من التحلل اللاهوائي وفقدان الكربون الناتج عن الاحتراق. ومع ذلك، فإن تحقيق إدارة ذكية مناخياً للأرز مع تحسين الغلة والأرباح الزراعية يمثل تحديًا بسبب المقايضات الاقتصادية والبيئية. يمكن تحقيق هذا التوازن بممارسات مناسبة خاصة بالموقع. يناقش هذا الفصل ممارسات إدارة القش هذه التي تؤثر على غازات الدفيئة المحسوبة بالمحصول وخيارات التخفيف في بيئات الأرز المختلفة.

AbstractThe research provided scientific evidences for improved rice straw management. Rice cultivation with in-field burning of rice straw is the worst option with the lowest energy efficiency and highest air pollution emission. This article comprises a comparative assessment of energy efficiency and the environmental footprint of rice production using four different rice straw management scenarios, namely, straw retained, straw burned, partial straw removal, and complete straw removal. Paddy yield, grain quality, and energy balance were assessed for two seasons while greenhouse gas emissions (GHGE) were measured weekly starting from land preparation through to the cropping and fallow period. Despite the added energy requirements in straw collection and transport, the use of collected rice straw for mushroom production can increase the net energy obtained from rice production systems by 10–15% compared to burning straw in the field. Partial and complete removal of rice straw reduces GHGE by 30% and 40% compared to complete straw retention, respectively.