M. A. Islam
Department of Environmental Science, Bangladesh Agricultural University, Mymensingh-2202
M. Mano*
Graduate School of Horticulture, Chiba University, Matsudo-Shi, 271 Chiba, Japan
M. S. Hossen,
Department of Environmental Science, Bangladesh Agricultural University, Mymensingh-2202
A. Miyata
National Institute for Agro-Environmental Sciences, Tsukuba, Japan
M. A. Baten
Department of Environmental Science, Bangladesh Agricultural University, Mymensingh-2202
Aman rice, Flowering, Ripening, Vegetative stage
Agriculture Farm, Bangladesh Agricultural University
Risk Management in Agriculture
Carbon sequestration
Geographical location of the study site This study was conducted in the Mymensingh flux study site, called MYM site (three letter international code name for Asia Flux). It is located in the Agriculture Farm, Bangladesh Agricultural University (24°43' 31.0"N or 24.72528°N, 90°25' 27.3"E or 90.42425 °E; 18 m above sea level), 6 km to the south of Mymensingh town and 115 km to the north of Dhaka, the capital city of Bangladesh. This extensive field (about 78.28 ha) has been used only for paddy cultivation for 54 years from the beginning of University in 1961, and provides sufficient upwind fetch (>300 m to the south, >500 m to the west, and about 200 m to the north and east of the measuring tower) of uniform cover required for measuring mass and energy fluxes using tower-based eddy covariance systems. Cropping patterns The rice growing period was two seasons: Boro (January to May) and Aman (August to December) in a year. Common cropping patterns using there since long are irrigated Boro rice, a fallow period, and rain feed Aman rice. The field was mostly flooded except ripening stage by rain fed water (Aman season) or irrigated water (Boro season). After Boro season there was no crop cultivated in the study area for about 90 days (middle May to middle August). Weeds and various aquatic plants were found to grow during the fallow period. After Aman season, on the other hand, crop residue was taken out and the field had no plants. In this study, we focused the diurnal CO2 flux pattern in Aman season. Rice was grown under recommended cultural practices under the active supervision of Central Farm Authority of Bangladesh Agricultural University. Observation was made without any influence on the rice paddy ecosystem to measure the status of radiation and energy balance. Flux measurement systems Eddy covariance (EC) measurement In our flux study site, flux densities of sensible heat and carbon dioxide and water vapor were measured by the eddy covariance method using a sonic anemometer (R3, Gill, UK) and an open-path infrared gas analyzer (LI7500, LICOR, USA). Three wind components and acoustic virtual temperature measured with the sonic anemometer, and densities of carbon dioxide and water vapor density measured with the infrared gas analyzer were sampled at 10 Hz interval (10 times per second), and recorded with a data logger (CR3000, Campbell Scientific, USA). Data collection and mathematical interpolation Data were collected weekly, and additional data processing (e.g. transfer files from the data logger, and file conversion from Binary to ASCII and) was done by our computers at Micrometeorology Laboratory, Department of Environmental Science, Bangladesh Agricultural University, Mymensingh. Maintenance Research team of the project (professors and scientists) checked the micro-meteorological instruments at an interval of 7 to 10 days. In case of serious problem, advice was taken from our collaborator scientists of NIAES, Tsukuba, Japan. NIAES team also visits 2 to 3 times in a year to check in details. Data were retrieved during instrument checking. In case of sensor problem of any kind, it was tried heart and soul to fix/repair without any delay. Leveling of radiation sensors (MR40, EKO, Japan) were checked regularly. Ventilators for temperature-humidity sensors (HMP45A, Vaisala, Finland) were checked once a year and dust accumulated in the ventilation tube was removed. We always put high attention to take care of all instruments. Data analysis Data analyses were performed using Microsoft Excel 2010 (Microsoft Corp.). Graphs were also prepared by the above mentioned software. Quality control of data Continuous measurement of meteorological data may introduce errors due to various causes, viz. malfunctioning of instruments, inappropriate atmospheric conditions, rainfall or human disturbance etc. So it is needed to control the quality of meteorological data. Graph of time series of half-hourly meteorological data were prepared and observed abnormalities such as discontinuities and unrealistic diurnal variations were flagged. After doing data quality, missing half-hourly values of incoming short-wave radiation, air temperature, relative humidity and barometric pressure were filled at NIAES Laboratory.
J. Environ. Sci. & Natural Resources, 9(2): 127-130, 2016 ISSN 1999-7361
Journal