Yield-scaled global warming potential of two irrigation management systems in a highly productive rice system

ABSTRACT Water management impacts both methane (CH4) and nitrous oxide (N2O) emissions from rice paddy fields. Although controlled irrigation is one of the most important tools for reducing CH4emission in rice production systems it can also increase N2O emissions and reduce crop yields. Over three years, CH4 and N2O emissions were measured in a rice field in Uruguay under two different irrigation management systems, using static closed chambers: conventional water management (continuous flooding after 30 days of emergence, CF30); and an alternative system (controlled deficit irrigation allowing for wetting and drying, AWDI). AWDI showed mean cumulative CH4 emission values of 98.4 kg CH4 ha−1, 55 % lower compared to CF30, while no differences in nitrous oxide emissions were observed between treatments ( p > 0.05). No yield differences between irrigation systems were observed in two of the rice seasons ( p > 0.05) while AWDI promoted yield reduction in one of the seasons ( p< 0.05). When rice yield and greenhouse gases (GHG) emissions were considered together, the AWDI irrigation system allowed for lower yield-scaled total global warming potential (GWP). Higher irrigation water productivity was achieved under AWDI in two of the three rice seasons. These findings suggest that AWDI could be an option for reducing GHG emissions and increasing irrigation water productivity. However, AWDI may compromise grain yield in certain years, reflecting the importance of the need for fine tuning of this irrigation strategy and an assessment of the overall tradeoff between relationships in order to promote its adoption by farmers

Comparison of bacterial communities of conventional and A-stage activated sludge systems

The bacterial community structure of 10 different wastewater treatment systems and their influents has been investigated through pyrosequencing, yielding a total of 283486 reads. These bioreactors had different technological configurations: conventional activated sludge (CAS) systems and very highly loaded A-stage systems. A-stage processes are proposed as the first step in an energy producing municipal wastewater treatment process. Pyrosequencing analysis indicated that bacterial community structure of all influents was similar. Also the bacterial community of all CAS bioreactors was similar. Bacterial community structure of A-stage bioreactors showed a more case-specific pattern. A core of genera was consistently found for all influents, all CAS bioreactors and all A-stage bioreactors, respectively, showing that different geographical locations in The Netherlands and Spain did not affect the functional bacterial communities in these technologies. The ecological roles of these bacteria were discussed. Influents and A-stage bioreactors shared several core genera, while none of these were shared with CAS bioreactors communities. This difference is thought to reside in the different operational conditions of the two technologies. This study shows that bacterial community structure of CAS and A-stage bioreactors are mostly driven by solids retention time (SRT) and hydraulic retention time (HRT), as suggested by multivariate redundancy analysis.Department of Civil EngineeringInstitute of Water Research from the University of GranadaDepartment of Environmental Biotechnology of the Delft University of Technolog

Bacterial Communities Involved in Soil Formation and PlantEstablishment Triggered by Pyrite Bioweathering on ArcticMoraines

Abstract In arctic glacier moraines, bioweathering primed by microbial iron oxidizers creates fertility gradients that accelerate soil development and plant establishment. With the aim of investigating the change of bacterial diversity in a pyrite-weathered gradient, we analyzed the composition of the bacterial communities involved in the process by sequencing 16S rRNA gene libraries from different biological soil crusts (BSC). Bacterial communities in three BSC of different morphology, located within 1 m distance downstream a pyritic conglomerate rock, were significantly diverse. The glacier moraine surrounding the weathered site showed wide phylogenetic diversity and high evenness with 15 represented bacterial classes, dominated by Alphaproteobacteria and pioneer Cyanobacteria colonizers. The bioweathered area showed the lowest diversity indexes and only nine bacterial families, largely dominated by Acidobacteriaceae and Acetobacteraceae typical of acidic environments, in accordance with the low pH of the BSC. In the weathered BSC, iron-oxidizing bacteria were cultivated, with counts decreasing along with the increase of distance from the rock, and nutrient release from the rock was revealed by environmental scanning electron microscopy-energy dispersive X-ray analyses. The vegetated area showed the presence of Actinomycetales, Verrucomicrobiales, Gemmatimonadales, Burkholderiales, and Rhizobiales, denoting a bacterial community typical of developed soils and indicating that the lithoid substrate of the bare moraine was here subjected to an accelerated colonization, driven by iron-oxidizing activity

Degradation of proteins and amino acids by Caloramator proteoclasticus in pure culture and in coculture with Methanobacterium thermoformicicum Z245

This study investigated the degradation of proteins and amino acids by Caloramator proteoclasticus, an anaerobic thermophilic (55 °C) fermentative bacterium isolated from an anaerobic bioreactor. Experiments were performed in the presence and absence of Methanobacterium thermoformicicum Z245, a methanogen that can use both hydrogen and formate for growth. Higher production rates and yields of the principal fermentation products from gelatin were observed in methanogenic coculture. The specific proteolytic activity in coculture tripled the value obtained in pure culture. C. proteoclasticus fermented glutamate to acetate, formate, hydrogen and alanine. In methanogenic coculture, a shift towards higher amounts of acetate and hydrogen with no alanine production was observed. Extracts of glutamate-grown cells possessed high activities of g-methylaspartase, a key enzyme of the mesaconate pathway leading to acetate. The presence of two enzymes (alanine-f-ketoglutarate aminotransferase and NADH-dependent alanine dehydrogenase) usually involved in the biosynthesis of alanine from pyruvate was also detected. The fermentation of amino acids known to be oxidatively deaminated (leucine and valine) was improved in the presence of both methanogenesis and glycine, a known electron acceptor in the Stickland reaction. Culture conditions seem to be very important in the way C. proteoclasticus disposes of reducing equivalents formed during the degradation of amino acids

Irrigation management and greenhouse gas emissions in Uruguayan rice production systems: abstract.

Environmental impact and sustainability of agricultural systems and management practices leading to climate change mitigationare one of the most relevant issues to agricultural production nowadays. Mitigation is the process of reducing emissions orenhancing sinks of greenhouse gases (GHG), to limit global warming potential and restrict future climate change. The mostrelevant GHG are Carbon dioxide (CO2), Methane (CH4) and Nitrous Oxide (N2O). The steady increase of its concentrationsin the atmosphere over several decades has led to enhance global warming. CH4 and N2O are the most relevant GHG emittedmainly in the agricultural sector. It is well known that water management has great impact on GHG emissions from rice paddyfields. One of the most important tools for rice crop production and mitigation of CH4 emission is the controlled irrigation.However, it could result in a N2O emission increase and reduced rice yields. For these reasons, it is remarkably important toassess the tradeoff relationship between both GHG and the effect on rice productivity. A 3 year field experiment with two differentirrigation systems was set at southeast of Uruguay. Conventional water management (continuous flooding after 30 days ofemergence, CF30) and an alternative irrigation system (controlled deficit irrigation allowing wetting and drying, AWDI) werecompared. The objective was to study the effect of water management on GHG emission, water productivity and rice yields inorder to identify strategies for further progress in sustainable intensification of Uruguayan rice. Results showed that meancumulative CH4 emission values for AWDI were 55% lower than CF30 systems; on the other hand, there were no significantdifferences in N2O emission among systems. Significant yield differences were not observed in two of the rice seasons, whileAWDI recorded a significant yield reduction in one of them. Total irrigation water applied and irrigation water productivity did notshowed differences in two of the rice seasons, while CF30 reported a higher amount of water applied and lower waterproductivity in one of the seasons. It can be concluded that AWDI could be an option to enhance water productivity and GHGemission mitigation. However, grain yield can be compromised in AWDI systems. The adoption of these technology is basedon the indispensable assess of an overall tradeoff between the risk of possible yield losses, total water used and GHGemissions

Season and no-till Rice crop intensification affect soil microbial populations involved in CH4 and N2O emissions.

Abstract: Rice is an important source of methane (CH4) and other crops may be sources of nitrous oxide (N2O), both of which are powerful greenhouse gases. In Uruguay, irrigated rice rotates with perennial pastures and allows high productivity and low environmental impact. A long-term experiment with contrasting rice rotation intensification alternatives, including rice?soybean and continuous rice, was recently carried out in an Argialboll located in a temperate region of South America. To know if rotation systems influence soil microbial activity involved in CH4 and N2O emissions, the abundance and potential rate for gas production or consumption of microbial populations were measured during the rice crop season. CH4 was only emitted when rice was flooded and N2O emission was not detected. All rotational soils showed the highest rate for methanogenesis at tillering (30 days after rice emergence), while for methanotrophy, the maximum rate was reached at flowering. The abundance of related genes also followed a seasonal pattern with highest densities of mcrA genes being observed at rice flowering whereas pmoA genes were more abundant in dry soils after rice harvest, regardless of the rotation system. Differences were found mainly at tillering when soils with two consecutive summers under rice showed higher amounts of mcrA and pmoA gene copies. The potential denitrification rate was highest at the tillering stage, but the abundance of nirK and nirS genes was highest in winter. Regarding ammonium oxidation, bacterial amoA abundance was higher in winter while the archaeal amoA gene was similar throughout the year. A strong influence of the rice growth stage was registered for most of the parameters measured in rice paddy soils in this no-till rice intensification experiment. However, differences among rotations begin to be observed mainly at tillering when the abundance of populations of the methane and nitrous oxide cycles seemed to respond to the rice intensification

Cinética de la producción y consumo de metano en suelos con rotación de arroz. [Resumen].

El metano (CH4) atmosférico es uno de los principales gases del efecto invernadero. En este trabajo se han estudiado las actividades metanogénicas y metanótrofas de suelos con distintas variantes en el manejo agrícola

Cuantificación de emisiones de metano y óxido nitroso bajo dos manejos de riego contrastantes en el cultivo de arroz.

El manejo del riego ha demostrado tener un impacto sobre las emisiones de metano (CH4) y óxido nitroso (N2O) en el cultivo de arroz. El riego con déficit controlado, el cual disminuye el período bajo inundación, ha sido reportado como una importante herramienta para atenuar las emisiones de metano. Sin embargo este manejo del riego podría incrementar las emisiones de óxido nitroso y reducir el rendimiento. Por lo tanto, es importante analizar las posibles compensaciones entre las emisiones de gases de efecto invernadero (GEI) y la productividad. A lo largo de tres años dos manejos del riego contrastantes fueron evaluados con respecto a las emisiones totales de metano y óxido nitroso, rendimiento, consumo y productividad del agua. Los manejos de agua estudiados fueron el manejo tradicional que consistió en el establecimiento de la inundación a los 30 días después de la emergencia (IC30) en comparación con un riego restringido con déficit controlado que permitía el secado y mojado del suelo (RR). RR presentó una acumulación media de metano de 98,4 kg/ha CH4, que fueron un 55% menores a los observados en IC30, mientras que no hubo diferencias significativas en las acumulaciones medias de óxido nitroso entre ambos tratamientos de riego. En dos de los años evaluados no hubo diferencias significativas de rendimiento entre los manejos del riego, mientras que el manejo RR presentó un rendimiento significativamente menor en uno de los años. No hubo diferencias en la totalidad de agua aplicada y en la productividad de la misma en dos de los años evaluados, mientras que el tratamiento IC30 presentó mayores niveles de agua aplicada y menor productividad del agua en uno de ellos. Estos resultados sugieren que el manejo del riego con déficit controlado (RR) puede ser una opción para reducir las emisiones GEI del cultivo de arroz. De todas formas, este manejo del riego puede comprometer el rendimiento del cultivo, determinando por lo tanto la importancia de la correcta evaluación de las incertidumbres y riesgos a la hora de promover su adopción por los productores