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International audienceIrrigation has a critical role for crop production worldwide. In particular, irrigation is a major issue due to the growing food demand and climate change. Irrigation affects yields and the emission of greenhouse gases such as CO2 and N2O by soils. Here, we review the effect of irrigation on soil organic carbon and N2O emissions. We analysed 22 investigations in various regions of the world. Interactions between irrigation, soil and management factors are described. The main points are: (1) The influence of irrigation is strongly dependent on climate and initial soil organic carbon content. For instance, irrigation of cultivated desert soils led to an average increase of 90 % to over 500 % of soil organic carbon. (2) Irrigation of semiarid regions increases soil organic carbon by 11 % to 35 %. (3) No consistent effects of irrigation were observed in humid regions. In many cases, N2O emissions increase after precipitation or irrigation. (4) Comparison of N2O emissions from irrigated and non-irrigated fields shows that availability of reactive nitrogen compounds controls increased N2O emissions under irrigation, in most cases. Here, increases of about 50 % to 140 % in N2O emissions were reported

After nearly two decades of subsidized and energy crop-oriented development, agricultural biogas production in Germany is standing at a crossroads. Fundamental challenges need to be met. In this article we sketch a vision of a future agricultural biogas plant that is an integral part of the circular bioeconomy and works mainly on the base of residues. It is flexible with regard to feedstocks, digester operation, microbial communities and biogas output. It is modular in design and its operation is knowledge-based, information-driven and largely automated. It will be competitive with fossil energies and other renewable energies, profitable for farmers and plant operators and favorable for the national economy. In this paper we discuss the required contribution of research to achieve these aims.

This study presents a cradle-to-gate assessment of the energy balances and greenhouse gas (GHG) emissions of Indonesian palm oil biodiesel production, including the stages of land-use change (LUC), agricultural phase, transportation, milling, biodiesel processing, and comparing the results from different farming systems, including company plantations and smallholder plantations (either out growers or independent growers) in different locations in Kalimantan and Sumatra of Indonesia. The findings demonstrate that there are considerable differences between the farming systems and the locations in net energy yields (43.6-49.2 GJ t À1 biodiesel yr À1) as well as GHG emissions (1969.6-5626.4 kg CO 2eq t À1 biodiesel yr À1 ). The output to input ratios are positive in all cases. The largest GHG emissions result from LUC effects, followed by the transesterification, fertilizer production, agricultural production processes, milling, and transportation. Ecosystem carbon payback times range from 11 to 42 years.

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Indicators for water use at farm scale can assist farmers in understanding the water flows on their farms and in optimizing water use by adapting agronomic measures and farm management. The objective of this work is to develop a methodology to estimate water flows at the farm scale, to derive indicators for farm water use, and to apply them in a first case study. After the spatial and temporal boundaries of the farm system and the water flows are defined, three indicators to assess water use at the farm scale are developed: farm water productivity, degree of water utilization, and specific inflow of technical water. Farm water productivity describes the ratio of farm output to water input, where the water input is the total of those water inflows into the farm system that can be assigned to the generation of farm output. Farm output is expressed on a mass basis, food energy basis, and monetary basis. The degree of water utilization characterizes the relationship between productive water to the total water inflow into the farm system, where productive water comprises those water flows that directly contribute to biomass generation via plant and animal metabolism. The specific technical water inflow quantifies the water inflow into the system by technical means relative to the farm area. The application of the methodology in a first case study for a mixed crop-livestock farm with 2869 ha in Germany results in a farm water productivity of 2.30 kg fresh mass per m approaches to optimize water use in farms are discussed as well as the further research required for practical implementation.

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Disturbances of the anaerobic digestion process reduce the economic and environmental performance of biogas systems. A better understanding of the highly complex process is of crucial importance in order to avoid disturbances. This review defines process disturbances as significant changes in the functionality within the microbial community leading to unacceptable and severe decreases in biogas production and requiring an active counteraction to be overcome. The main types of process disturbances in agricultural biogas production are classified as unfavorable process temperatures, fluctuations in the availability of macro- and micronutrients (feedstock variability), overload of the microbial degradation potential, process-related accumulation of inhibiting metabolites such as hydrogen (H2), ammonium/ammonia (NH4+/NH3) or hydrogen sulphide (H2S) and inhibition by other organic and inorganic toxicants. Causes, mechanisms and effects on the biogas microbiome are discussed. The need for a knowledge-based microbiome management to ensure a stable and efficient production of biogas with low susceptibility to disturbances is derived and an outlook on potential future process monitoring and control by means of microbial indicators is provided.