ARS 2013

3 rd Annual Research Session

2013-12-01T00:00:00Z

3 rd Annual Research Session

Digestibility and expected glycemic index of high amylose rice varieties with similar amylose content and gelatinization temperature

2013-12-01T00:00:00Z

Digestibility and expected glycemic index of high amylose rice varieties with similar amylose content and gelatinization temperature Gunaratne, Anil; Corke, Harold Six high amylose rice varieties with nearly similar amylose content (30%) and gelatinization temperature (77 ⁰C), but differing in size (length/width) were cooked under the same cooking conditions and their physicochemical properties, digestibility and expected glycemic index were investigated and compared. Resistant starch content ranged from 0.48 to 1.6. Expected in Vitro glycemic index was nearly 116 for all tested varieties. The results showed that the size (length/width) and resistant starch content have apparently no impact on the glycemic index of tested six rice varieties. It appears that the dominant factors that determine the glycemic index of tested rice varieties were amylose content and the gelatinization temperature. Except for pasting temperature, other pasting properties obtained by RVA (Rapid Visco-Analyzer) test significantly varied among the tested six rice varieties. Pasting temperature corresponds to the gelatinization temperature. Thus, pasting properties, except for pasting temperature are not good predictors for the glycemic index of high amylose rice.

Climate change impact on rice farming systems in Sri Lanka

2013-12-01T00:00:00Z

Climate change impact on rice farming systems in Sri Lanka Karunaratne, A. S; Nissanka, S.P; Weerakoon, W.M.W; Zubair, L; Ruane, A; McDermid, S The Agricultural Model Intercomparison and Improvement Project (AgMIP) is a major international effort linking the climate, crop, and economic modeling communities with cutting-edge information technology to produce improved crop and economic models and the next generation of climate impact projections for the agricultural sector. The coordinated climate-crop modelling project (C3MP) is one of the global assessments in AgMIP. C3MP mobilizes international crop modellers for a coordinated investigation of climate vulnerability and climate change impacts on agriculture aim to improve understanding of the impact of climate change on future agricultural production by utilizing site-calibrated crop models to coordinate projections of crop response under probabilistic climate change scenarios. In line with AgMIP’s attempts to develop adaptation to climate change for agricultural sector globally and regionally, the AgMIP-Sri Lanka project investigated the climate change impacts on rice based farming systems and adaptation strategies, led by the Stakeholder Institutes of Department of Agriculture and Agricultural Universities. Commonly cultivated rice varieties (Bg300, Bg358, Bg357) in major rice growing region (Kurunegala) where information on rice production of farm families are available was selected for the present study. DSSAT model was calibrated using experimental data obtained from the Rice Research and Development Institute (RRDI). Rice yield was simulated for 104 farmer fields for two growing seasons (major and minor) for the base years (2012- 2013), baseline period (1980-2010), and mid-century (2040-2069) for five GCMs (CCSM4, GFDL-ESM2M, HadGEM2-ES, MIROC5, MPI-ESM-MR) of RCP-8.5 scenario. According to the C3MP protocol, 99 sensitivity tests were performed for Bg 300 and Bg 357 for RRDI experimental site in both major (maha) and minor (yala) seasons. Climate sensitivity tests were performed by adjusting historical climate to reflect changes to temperature, precipitation and [CO2]. The base year (2012/2013) RMSE for both seasons range around 1200-1300 kg/ha for observed (major-season 4289kg/ha; minor-season 3883kg/ha) vs simulated using DSSAT (major-season 4888kg/ha; minor-season 4410kg/ha). Compared to baseline period (1980-2010), a significant yield reduction of 14%, 12%, 22%, 12%, 17% for the major-season and 31%, 30%, 42%, 28%, 35% minor-season, for the above five GCMs, was observed respectively. C3MP Coordinators provided a bias-adjusted MERRA Reanalysis weather time series corresponding to the site. DSSAT model predictions were submitted via a provided template to the C3MP Coordination team. The archived results were vetted and fit with an emulator to estimate yield response surfaces. These response surfaces may then be used to analyze the impacts of projected climate changes.

Deep ploughing adversely affects on soil water conservation in light soils

2013-12-01T00:00:00Z

Deep ploughing adversely affects on soil water conservation in light soils Vidhana Arachchi, Lal P Deep ploughing is the one of options to alleviate soil compaction and upgrade low productive lands for better crop production. However, deep ploughing should be implemented with the knowledge of land characters. Field experiments were conducted to evaluate the effect of deep ploughing on soil water conservation in light soils in the Intermediate climatic zone of Sri Lanka. Soil compaction of different soil series was evaluated using bulk density and penetrometer resistance, through which selected the suitable soil series to evaluate deep ploughing on soil water conservation. Soil water storage with respect to deep ploughing was monitored during the dry and rainy seasons using neutron scattering technique. Evaluation of soil physical properties showed that the range of mean values of bulk density (BD) and soil penetration resistance (SPR) in the surface soil (0-10 cm depth) of major soil series in coconut lands was from 1.38  0.02 to 1.57  0.07 g/cm3 and 55  10 to 315  16.4 N/cm2 respectively. The total available water fraction increased with clay content of soil as a result of high micropores. However, due to soil compaction, ability of soils to conserve water and to remain aerated was low for those series. Deep ploughing during the rainy and dry periods in highly compacted soils (BD >1.5 g/cm3 and SPR >250 N/cm2 ) greatly increased conserved soil water in the profile, while in less compacted light soils (BD <1.5 g/cm3 and SPR <250 N/cm2 ) conserved water content was adversely affected. Soil water retention in bare soils of both highly and less compacted light soil series was higher than that of live grass-covered soil. In addition, deep ploughing even in the effective root zone with live grass-covered highly compacted soils around coconut tree was favorable for soil water retention compared to that of live grass covered less compacted soils.