ASSESSING RICE YIELD FOR FUTURE CLIMATE IN MONERAGALA DISTRICT, SRI LANKA

Abstract

Yield reduction due to climate induced stresses is a major constraint to agriculture in tropical region and rice is one of the severely affected crops. Monaragala is one of the important agricultural areas in Sri Lanka where intensive rice farming is practiced. Therefore, this study was conducted (i) to project the future climate for 2040–2065 period using general circulation models (GCMs) of 5th phase of Coupled Model Intercomparison Project (CMIP5) archive and compare with baseline period of 1980-2009 climate and (ii) to simulate rice yield in mid-21st century using crop modelling approach, in Moneragala district, Sri Lanka. Due to the lack of consistent and long-term meteorological data in the study area, NASA Prediction of Worldwide Energy Resource (POWER) data were used for the baseline period. Future climate and the yield were assessed using 3 GCMs (gfdl esm2m, mpi esm mr and ncc noresm1 m) under high greenhouse gas emission scenario (RCP8.5). Yield of four rice varieties (Bg 300, 308, 357 and 358) were simulated using a previously calibrated Agricultural Production Systems Simulator (APSIM) Oryza model. The average annual rainfall of the region showed an increasing trend as it increased by 47 mm per year during 1980–2009 period. The increment of Maha season rainfall (32 mm/year) was higher than the Yala season (16 mm/year). On average, annual rainfall increased by 30.5% in mid-21st century (2040–2065) with compared to the baseline period. All the GCMs recorded an increment of both minimum and maximum temperatures for both seasons. Rice yield projections for mid century showed a considerable diversity among GCMs and varieties. Out of the four varieties, Bg 358 recorded a yield increment in both Yala (2.1%) and Maha (4.2%) seasons while all other varieties showed a yield reduction. A comparatively higher yield reduction was predicted in Maha (2.4%) than Yala (0.5%) season under mid-century climate. Since rice yield in Moneragala district is expected to decline with the climate change, adaptation strategies are needed to minimize the yield losses.