Coastal Bangladesh experiences significant poverty and hazards today and is highly vulnerable to climate and environmental change over the coming decades. Coastal stakeholders are demanding information to assist in the decision making processes, including simulation models to explore how different interventions, under different plausible future socio-economic and environmental scenarios, could alleviate environmental risks and promote development. Many existing simulation models neglect the complex interdependencies between the socio-economic and environmental system of coastal Bangladesh. Here an integrated approach has been proposed to develop a simulation model to support agriculture and poverty-based analysis and decision-making in coastal Bangladesh. In particular, we show how a simulation model of farmer's livelihoods at the household level can be achieved. An extended version of the FAO's CROPWAT agriculture model has been integrated with a downscaled regional demography model to simulate net agriculture profit. This is used together with a household income-expenses balance and a loans logical tree to simulate the evolution of food security indicators and poverty levels. Modelling identifies salinity and temperature stress as limiting factors to crop productivity and fertilisation due to atmospheric carbon dioxide concentrations as a reinforcing factor. The crop simulation results compare well with expected outcomes but also reveal some unexpected behaviours. For example, under current model assumptions, temperature is more important than salinity for crop production. The agriculture-based livelihood and poverty simulations highlight the critical significance of debt through informal and formal loans set at such levels as to persistently undermine the well-being of agriculture-dependent households. Simulations also indicate that progressive approaches to agriculture (i.e. diversification) might not provide the clear economic benefit from the perspective of pricing due to greater susceptibility to climate vagaries. The livelihood and poverty results highlight the importance of the holistic consideration of the human-nature system and the careful selection of poverty indicators. Although the simulation model at this stage contains the minimum elements required to simulate the complexity of farmer livelihood interactions in coastal Bangladesh, the crop and socio-economic findings compare well with expected behaviours. The presented integrated model is the first step to develop a holistic, transferable analytic method and tool for coastal Bangladesh.

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ABSTRACT.The experiment was conducted during Rabi season of 2015-2016 and 2016-2017 at the Regional Agricultural Research station, BARI, Ishurdi, Pabna, Bangladesh, to determine the water requirements of wheat on raised bed and the effect of different deficit irrigation on yield, water use efficiency and applied water productivity under raised bed wheat. This study consisted of following irrigation treatments: T 1 = Irrigations up to 100% field capacity (FC) at crown root initiation (CRI), botting and grain filling stages (flat bed), T 2 = Irrigations up to 100% FC at CRI, botting and grain filling stages on raised bed, T 3 = Irrigations up to 80% FC at CRI, botting and grain filling stages on raised bed and T 4 = Irrigations up to 60% FC at CRI, botting and grain filling stages on raised bed and laid out in a randomize complete block design with three replications.The result showed that significant effect of irrigation treatments were observed on plant height, spike per m 2 and grain yield. Highest grain yield (4.66 t/ha) was obtained from treatment, irrigations up to 100% FC at CRI, botting and grain filling stages on raised bed, followed by irrigation up to 100% FC at same stages on flat bed. At raised bed wheat cultivation saving 14.30% water with increasing 15.66% grain yield than flat bed. Besides, comparing deficit irrigation (20% and 40% of full irrigation) and full irrigation condition on raised bed seeding system water use could be reduced about 4.18% to 5.57%, while scarifying 18.20% to 32.33% grain yield, where reduced 14.17% to 27.54% water use efficiency. Maximum applied water productivity 1.81 kg m -3 was observed in raised bed full irrigation condition. The rate of daily evaporation started to increase as the temperature started to rise and humidity started to decrease during the crop growing period. The results will be helpful for taking policy decision regarding efficient irrigation and water management under prevailing water scarce situation.

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