J.C.Biswas
Soil Science Division, Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh
M.B.Hossain
Irrigation and Water Management Division, Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh
A.K. Choudhury
OFRD, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh
N. Kalra
Indian Agricultural Research Institute, New Delhi, India
M. Maniruzzaman*
Irrigation and Water Management Division,Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh
T.Amanrice yield, Climatic variability, MAKESENS model.
Bangladesh Rice Research Institute, Gazipur
Variety and Species
Site description The research was carried out at Bangladesh Rice Research Institute, Gazipur during 2015-16. The north-west part of Bangladesh is situated at 23o47'45"N to 25o46'34"N latitude and 88o00'37"E to 89o49'11"E longitude and covers an area of about 23,295 km2. It is composed of 4 districts those belong to Rajshahi region (Rajshahi, C. Nawabganj, Natore and Pabna), 4 districts under Rangpur region (Rangpur, Gaibandha, Kurigram and Lalmonirhat), 4 districts under Dinajpur region (Dinajpur, Nilphamari, Thakurgaon and Panchagarh) and 4 districts under Bogra region (Bogra, Joypurhat, Naogaon and Sirajganj). Total population of that area is 22.93 million of which more than 80% of people live in rural areas those who mainly depend on agriculture. The density of population is about 860 people km-2. The study area is relatively dry humid in which the annual average rainfall is 1,400-1,900 mm. Almost 92.7% rainfall occurs during May to October. The inter-annual variability of non-monsoonal rainfall is more than 50% (Shahid, 2008). Temperature ranges from 25oC to 40oC in the hottest season and 8oC to 25oC in the coolest one. About 90% land area is used for wet season rice cultivation. High-yielding T.Aman rice varieties are dominant and shares almost 95% of total cultivated crop in wet season (BBS, 2013), which is threatened frequently by drought (Shahid, 2008). In the last 40 years, the area suffered by 8 droughts of major magnitude. Farmers use supplemental irrigation water to avoid drought effects wherever possible. 2.2 Data source and temporal trend analysis: Temperature, rainfall and sunshine duration data from 1971-2010 were obtained from four stations of Bangladesh Meteorological Department (BMD) and rice grain yield data were collected from the Bangladesh Bureau of Agricultural Statistics for the whole north-west districts. The Mann–Kendall trend test (Mann, 1945) was used to detect trends in time series data and the test statistic distribution was explained by Kendall (1975) for testing non-linear trends and turning points. The test assumes a monotonic trend and thus rejects the presence of any seasonal or other cycles in the data. The Mann-Kendall test is preferred when various stations are tested in a single study (Hirsch et al., 1991). Sen’s slope estimator was used to determine the magnitude of change in the climatic parameter. The present study computed the confidence interval at p = 0.01 and p = 0.05. Representative Concentration Pathway (RCP) based projected data on temperature and rainfalls were used as an average of Geophysical Fluid Dynamics Laboratory’s Earth System Model (GFDL-ESM2M), Hadley Centre Global Environment Model version 2 Earth System Model (HadGEM2-ES), Institute Pierre Simon Laplace Low-Resolution Climate System Model Version SA (IPSL-CMSA-LR), Model for Interdisciplinary Research on Climate version 5 (MIROC5) and Meteorological Research Institute Coupled Global Climate Model version 3 (MRI-CGCM3). The projected data of 2050 and 2100 were compared with an average of 2001-2010 data, to judge the future projection with the present time normal trend. Four pathways: RCP8.5 (>8.5 W m-2by 2100), RCP6 (6 W m-2after 2100), RCP4.5 (4.5 W m-2after 2100) and RCP2.6 (3 W m-2before 2100 and then declines) -the last is also referred to as RCP3-PD was considered in the present investigation. Trend analyses for inter-annual and inter-seasonal, maximum, minimum and mean temperatures, rainfall and sunshine duration were carried out for those four locations. The descriptive statistics for the yield of T.Aman rice and seasonal climatic elements were prepared. Growth rates of area and productivity of T.Amanrice were worked out as decadal basis by using the following formula: Growth rate= (X2 –X1)/ No. of years -------(1) Where, X2 = calculated decadal year, area or yield X1 = previous decadal year, area or yield annual and seasonal deviations of temperature, rainfall and sunshine hours and yield from the trend line were computed as follows (Maniruzzaman et al., 2017):
Several T. Aman varieties are grown in the test regions, but for the convenience of the climate change impact study average grain yield of all T. Aman varieties (as reported in BBS records) cultivated in the tested locations was considered as the idiotypic response of variety.
The Agriculturists 15(1): 68-80(2017) ISSN 2304-7321 (Online), ISSN 1729-5211 (Print)
Journal