Abul Fazal M. Saleh

Crop and rain water management strategies for increasing productivity of rainfed lowland rice systems

Abstract The timing, frequency and amount of rainfall during the growing season determine the land productivity in a rainfed environment. For increasing productivity and stabilizing yield, technologies and strategies that minimize the effects of uncertainties in water availability are needed. This study, conducted in northern Luzon, Philippines, during 1991–1992, established the benefits of the dry seeding technique of rice crop establishment over the traditional transplanted method. During the study period, farmers with dry seeded rice (DSR) were able to establish the crop about 40 days earlier than transplanted rice (TPR) and utilized about 400 mm of the initial monsoon rains. The advantage of DSR is reflected in higher expected seasonal relative water supply (RWS) values of 1·08 at 50% and 1·04 at 75% probability, compared to 1·04 and 0·52, respectively, for TPR. Thus, crop water availability would not be a problem for either system of rice culture in an average year, but TPR would be severely affected by water shortage once every 4 years. DSR was harvested about 10 days earlier than TPR and provided a better soil-water regime for the following upland crop. In an average year, farmers growing mungbean after DSR can expect to meet 50% of the potential crop water requirement from rainfall compared to 37% for those who grow mungbean after TPR. The average yield of DSR was equal to that of TPR during the study period, but the significantly higher yields of mungbean grown after the DSR substantially increased the productivity of the rainfed lowland rice systems.

Evaluation of some deep and shallow tubewell irrigated schemes in Bangladesh using performance indicators

Abstract Performances of five deep tubewell (DTW) and ten shallow tubewell (STW) projects of the Rajbari district of central Bangladesh have been evaluated using some selected standard indicators, broadly classified into three groups: hydraulic, agricultural and socio-economic. For the quantitative and qualitative assessments of the indicators, field measurements and questionnaire survey of farmers and tubewell owners were made during the 1998–99 dry season. Analyses of hydraulic indicators showed that the performances of both the projects (DTWs and STWs) in terms of discharge and water delivery were better than those in the past. Equity in water delivery was not ensured in both the projects mainly because of low canal density. Agricultural performance, evaluated in terms of irrigated area, yield and production performance, was almost the same for both the projects and was greater than the respective national averages. Socio-economic indicators showed that both the projects were financially viable and sustainable. Hydraulic, agricultural and socio-economic indicators used in this study are recommended for evaluation of performances of irrigation projects and also for comparative analysis of performances of similar irrigation projects.

Integrative Analysis Applying the Delta Dynamic Integrated Emulator Model in South-West Coastal Bangladesh

A flexible meta-model, the Delta Dynamic Integrated Emulator Model (ΔDIEM), is developed to capture the socio-biophysical system of coastal Bangladesh as simply and efficiently as possible. Operating at the local scale, calculations occur efficiently using a variety of methods, including linear statistical emulators, which capture the behaviour of more complex models, internal process-based models and statistical associations. All components are tightly coupled, tested and validated, and their behaviour is explored with sensitivity tests. Using input data, the integrated model approximates the spatial and temporal change in ecosystem services and a number of livelihood, well-being, poverty and health indicators of archetypal households. Through the use of climate, socio-economic and governance scenarios plausible trajectories and futures of coastal Bangladesh can be explored.

Prospects for Agriculture Under Climate Change and Soil Salinisation

Agriculture is the largest and most important provisioning ecosystem in the Ganges-Brahmaputra-Meghna delta and is significantly affected by levels of soil and water salinity. Model-based assessment using both soil moisture and salt balance models indicate that whilst monsoon rains supply adequate water to grow a main season rice crop, agricultural diversity is currently constrained by the limited availability of good quality irrigation water in the dry season. There is a tipping point of water salinity around four parts per thousand beyond which soil salinity accumulates. Although the development of soil salinity is an environmental process, soil salinisation is closely linked to farmers’ behaviour and land use practices. It is also closely associated with the decline in other ecosystem services associated with water regulation.