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Title:
Annual Report 2015
Description:

keyword:
N/A



Title:
Main Achievements of Research and Technology Development for Crop Production (2015-2016)
Description:

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Title:
Main Achievements of Research and Technology Development for Crop Production (2016-2017)
Description:

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Title:
INFLUENCE OF TEMPERATURE AND HUMIDITY REGIMES ON THE DEVELOPMENTAL STAGES OF GREEN VEGETABLE BUG, NEZARA VIRIDULA (L.) (HEMIPTERA: PENTATOMIDAE) FROM INLAND AND COASTAL POPULATIONS IN AUSTRALIA, by Pol Chanthy , Robert J. Martin , Robin V. Gunning and Nigel R. Andrew. GEN. APPL. ENT. VOL 43, 2015
Description:
Summary
Laboratory studies were conducted to assess impacts of temperature and humidity regimes on the development of Nezara​ viridula (L.) (Hemiptera: Pentatomidae) from inland and coastal populations in NSW, Australia. Four temperature regimes, 25±2ºC, 30±2ºC, 33±2ºC, and 36±2ºC and two humidity regimes, 40±10% and 80±10% RH were applied in the experiment with a constant photoperiod of 14:10 h (L:D). The developmental time of the nymphal stage of N. viridula significantly decreased with increasing temperature. Percentage nymphal survival significantly decreased with increasing temperature or high humidity (80% RH) regimes. Longevity of N. viridula adults declined with increasing temperature or high humidity regimes and femalelongevity was longer than males. High temperatures (30, 33 and 36ºC) or high humidity significantly reduced reproductive performance and capacity of N. viridula compared to low temperature (25ºC) or low humidity (40% RH). However, high humidity significantly increased egg hatchability of N. viridula compared with a low humidity regime. Interactions of temperature and humidity regimes significantly changed incubation period, adult longevity, mating frequency, pre-mating period, egg-mass size and egg hatchability of N. viridula. Interactions of population location (coastal or inland), temperature andhumidity regimes significantly changed incubation period and pre-oviposition period of N. viridula. Temperature and humidity are important environmental factors for the development and reproduction of N. viridula. Higher temperatures shorten the length of nymphal duration, but reduce nymphal survival. The optimum temperature for the development and reproduction of N.viridula was 25ºC with 40 ± 10% RH. No differences in nymphal duration, nymphal survival, adult longevity or reproduction performance between inland and coastal N. viridula populations were found under different climate conditions. We show the importance of assessing all life-stages in the response to varying temperature and humidity regimes, especially in terms of assessing responses to climate change.

Full article
keyword:
Pentatomidae; climate change; nymph, adult; life history;!insect; agriculture.
Summary
Laboratory studies were conducted to assess impacts of temperature and humidity regimes on the development of Nezara​ viridula (L.) (Hemiptera: Pentatomidae) from inland and coastal populations in NSW, Australia. Four temperature regimes, 25±2ºC, 30±2ºC, 33±2ºC, and 36±2ºC and two humidity regimes, 40±10% and 80±10% RH were applied in the experiment with a constant photoperiod of 14:10 h (L:D). The developmental time of the nymphal stage of N. viridula significantly decreased with increasing temperature. Percentage nymphal survival significantly decreased with increasing temperature or high humidity (80% RH) regimes. Longevity of N. viridula adults declined with increasing temperature or high humidity regimes and femalelongevity was longer than males. High temperatures (30, 33 and 36ºC) or high humidity significantly reduced reproductive performance and capacity of N. viridula compared to low temperature (25ºC) or low humidity (40% RH). However, high humidity significantly increased egg hatchability of N. viridula compared with a low humidity regime. Interactions of temperature and humidity regimes significantly changed incubation period, adult longevity, mating frequency, pre-mating period, egg-mass size and egg hatchability of N. viridula. Interactions of population location (coastal or inland), temperature andhumidity regimes significantly changed incubation period and pre-oviposition period of N. viridula. Temperature and humidity are important environmental factors for the development and reproduction of N. viridula. Higher temperatures shorten the length of nymphal duration, but reduce nymphal survival. The optimum temperature for the development and reproduction of N.viridula was 25ºC with 40 ± 10% RH. No differences in nymphal duration, nymphal survival, adult longevity or reproduction performance between inland and coastal N. viridula populations were found under different climate conditions. We show the importance of assessing all life-stages in the response to varying temperature and humidity regimes, especially in terms of assessing responses to climate change.

Full article
Title:
Assessing rice productivity and adaptation strategies for Southeast Asia under climate change through multi-scale crop modeling, by Jong Ahn Chun, Sanai Li, Qingguo Wang, Woo-Seop Lee, Eun-Jeong Lee, Nina Horstmann, Hojeong Park, Touch Veasna, Lim Vanndy, Khok Pros, Seng Vang, J.A. Chun et al. / Agricultural Systems 143 (2016) 14–21
Description:

Abstract
Rice (Oryza sativa L.) is one of the most important staple food crops in Southeast Asia, a region that is also partic- ularly vulnerable to climate change. We introduced a multi-scale crop modeling approach to assess the impacts of climate change on future rice yields in Southeast Asia. National- and farmer-level adaptation strategies may be developed by combining the advantages from regional- and field-scale crop models. Climate variables collected from the COordinated Regional climate Downscaling EXperiment (CORDEX)-East Asia were used as inputs to run the GLAM-Rice and CERES-Rice crop models. Simulations produced by the GLAM-Rice model identified Cambodia as the country in Southeast Asia where the reduction in rice yields under climate change will be the largest (a decrease of approximately 45% in the 2080s under RCP 8.5, relative to the baseline period 1991– 2000) without adequate adaptation. The results of the model simulations considering the CO2 fertilization effect showed that improved irrigation will largely increase rice yields (up to 8.2–42.7%, with the greatest increases in yields in Cambodia and Thailand) in the 2080s under RCP 8.5 compared to a scenario without irrigation. In addi- tion, the grid cell that will benefit the most (12.6 °N and 103.8 °E) was identified through further investigation of the spatial distribution of the effects of irrigation for Cambodia. For this grid cell, the CERES-Rice model was used to develop the best combination of adaptation measures. The results show that while a doubled application rate of nitrogen fertilizer (100 kg N ha−1 ) will increase rice yields by 3.9% in the 2080s under the RCP 4.5 scenario for the Sen Pidao cultivar, a decrease in rice yield was projected for the Phka Rumduol cultivar under RCP 4.5. For both cultivars, the results show that additional adaptation strategies besides the 100 kg N ha−1 fertilizer applica- tion rate and planting adjustment should be applied in order to offset all of the negative projected impacts of cli- mate change on rice yields in the 2080s under RCP 8.5. It is concluded that this study can be useful to enhance food security in Southeast Asia by providing informed recommendations for efficacious adaptation strategies.

Full article
 
keyword:
GLAM-Rice, CERES-Rice, Multi-scale crop modeling, Rice yield, Food security

Abstract
Rice (Oryza sativa L.) is one of the most important staple food crops in Southeast Asia, a region that is also partic- ularly vulnerable to climate change. We introduced a multi-scale crop modeling approach to assess the impacts of climate change on future rice yields in Southeast Asia. National- and farmer-level adaptation strategies may be developed by combining the advantages from regional- and field-scale crop models. Climate variables collected from the COordinated Regional climate Downscaling EXperiment (CORDEX)-East Asia were used as inputs to run the GLAM-Rice and CERES-Rice crop models. Simulations produced by the GLAM-Rice model identified Cambodia as the country in Southeast Asia where the reduction in rice yields under climate change will be the largest (a decrease of approximately 45% in the 2080s under RCP 8.5, relative to the baseline period 1991– 2000) without adequate adaptation. The results of the model simulations considering the CO2 fertilization effect showed that improved irrigation will largely increase rice yields (up to 8.2–42.7%, with the greatest increases in yields in Cambodia and Thailand) in the 2080s under RCP 8.5 compared to a scenario without irrigation. In addi- tion, the grid cell that will benefit the most (12.6 °N and 103.8 °E) was identified through further investigation of the spatial distribution of the effects of irrigation for Cambodia. For this grid cell, the CERES-Rice model was used to develop the best combination of adaptation measures. The results show that while a doubled application rate of nitrogen fertilizer (100 kg N ha−1 ) will increase rice yields by 3.9% in the 2080s under the RCP 4.5 scenario for the Sen Pidao cultivar, a decrease in rice yield was projected for the Phka Rumduol cultivar under RCP 4.5. For both cultivars, the results show that additional adaptation strategies besides the 100 kg N ha−1 fertilizer applica- tion rate and planting adjustment should be applied in order to offset all of the negative projected impacts of cli- mate change on rice yields in the 2080s under RCP 8.5. It is concluded that this study can be useful to enhance food security in Southeast Asia by providing informed recommendations for efficacious adaptation strategies.

Full article
 
Title:
Effects of straw mulch on mungbean yield in rice fields with strongly compacted soils, by Som Bunna, Pao Sinath, Ouk Makara, Jaquie Mitchell, Shu Fukai. Field Crops Research 124 (2011) 295–301
Description:

Abstract
In rice-based lowland areas in the Mekong region, the lack of full irrigation water availability for post-rice legume crops and the poor soil physical and chemical conditions are major constraints for development of sound rice/legume double cropping system. In order to improve legume productivity, use of rice straw mulch and various crop establishment methods were examined in two series of mungbean experiments in Cambodia where soils were coarse and strongly compacted. In one set of experiments conducted at four locations in the first year the effect of straw mulch, planting method (manual vs seed drill) and tillage method (conventional vs no-till) was examined. Another set of experiments were conducted in the second year at three locations with four levels of mulch under two planting densities. On average in year 1, mulching of rice straw at 1.5 t/ha increased mungbean crop establishment from 72 to 83%, reduced weed biomass from 164 to 123 kg/ha and increased yield from 228 to 332 kg/ha. Mulch was effective in conserving soil moisture, and even at maturity the mulched area had on average 1% higher soil moisture content. The amount of mulch between 1 and 2 t/ha did not show consistent effects in year 2, partly because some mulch treatments resulted in excessive soil moisture content and were not effective. Rice straw mulch had a significant effect on mungbean yield in 6 out of the 7 experiments conducted in two years, and mean yield increase was 35%. This yield advantage was attributed to better crop establishment, improved growth and reduced weed pressure, but in some cases only one or two of these factors were effective. On the other hand, planting method, tillage method and planting density had only small effects on mungbean yield in most experiments. Only in one location out of four tested, the no-till treatment produced significantly higher yield than the conventional method. Seed drill produced similar mungbean establishment and grain yield to the manual planting suggesting that the planter can be used to save the labour cost which is increasing rapidly in the Mekong region. Maximum root depth varied little with mulch or planting density, and was shallow (<20 cm) in all three locations where this character was determined. It is concluded that while rice straw mulch increased yield of mungbean following rice, the inability of mungbean roots to penetrate the hard pan is a major constraint for development of a sound rice/mungbean cropping system in the lowlands with compacted soils.

Full article
 

keyword:
Lowland rice field Mungbean Straw mulch Crop establishment Weed biomass

Abstract
In rice-based lowland areas in the Mekong region, the lack of full irrigation water availability for post-rice legume crops and the poor soil physical and chemical conditions are major constraints for development of sound rice/legume double cropping system. In order to improve legume productivity, use of rice straw mulch and various crop establishment methods were examined in two series of mungbean experiments in Cambodia where soils were coarse and strongly compacted. In one set of experiments conducted at four locations in the first year the effect of straw mulch, planting method (manual vs seed drill) and tillage method (conventional vs no-till) was examined. Another set of experiments were conducted in the second year at three locations with four levels of mulch under two planting densities. On average in year 1, mulching of rice straw at 1.5 t/ha increased mungbean crop establishment from 72 to 83%, reduced weed biomass from 164 to 123 kg/ha and increased yield from 228 to 332 kg/ha. Mulch was effective in conserving soil moisture, and even at maturity the mulched area had on average 1% higher soil moisture content. The amount of mulch between 1 and 2 t/ha did not show consistent effects in year 2, partly because some mulch treatments resulted in excessive soil moisture content and were not effective. Rice straw mulch had a significant effect on mungbean yield in 6 out of the 7 experiments conducted in two years, and mean yield increase was 35%. This yield advantage was attributed to better crop establishment, improved growth and reduced weed pressure, but in some cases only one or two of these factors were effective. On the other hand, planting method, tillage method and planting density had only small effects on mungbean yield in most experiments. Only in one location out of four tested, the no-till treatment produced significantly higher yield than the conventional method. Seed drill produced similar mungbean establishment and grain yield to the manual planting suggesting that the planter can be used to save the labour cost which is increasing rapidly in the Mekong region. Maximum root depth varied little with mulch or planting density, and was shallow (<20 cm) in all three locations where this character was determined. It is concluded that while rice straw mulch increased yield of mungbean following rice, the inability of mungbean roots to penetrate the hard pan is a major constraint for development of a sound rice/mungbean cropping system in the lowlands with compacted soils.

Full article
 

Title:
Ecophysiological study on weed seed banksand weeds in Cambodian paddy fields with contrasting water availability, by AKIHIKO KAMOSHITA, HIROYUKI IKEDA, JUNKO YAMAGISHI, MAKARA OUK, Weed Biology and Management 10, 261–272 (2010)
Description:

Abstract
Weed infestations are a major cause of yield reduction in rice (Oryza sativa) cultivation, particu-larly with direct-seeding methods, but the relationship between weed dynamics and wateravailability in Cambodian paddy fields has not been documented previously.We surveyed theweed abundance and weed seed banks in the soil of paddy fields with inferred differences intheir water regime in 22 farm fields in three provinces of Cambodia in the 2005 and 2006 rainy seasons.We studied rainfed lowland fields in upslope and downslope topographic positions andfields at different distances from the irrigation water source inside an irrigation rehabilitation area.The weed seed banks were estimated by seedling emergence in small containers and weedabundance and vigor were estimated by a simple scoring system.The estimated weed seed bankin the top 5 cm of soil ranged from 52.1 to 167 * 103 seeds m-2 (overall mean of 8.5 * 103 seeds m-2) and contained a high proportion (86%) of sedge species, such as Fimbristylis miliacea L. and Cyperus difformis. Several fields had particularly large seed banks, including one near the reservoir. No clear difference was found in the weed seed banks between the irrigated fields thatwere located close to (upstream) and distant from (downstream) the water source or betweenthe irrigated and rain-fed lowland fields, but the weed scores were larger in the rain-fed fieldsand the downstream fields within the irrigated area. A water shortage during the late growingseason in 2005 led to a proliferation of weeds in some fields and an associated increase in weedseedbank size in 2006. However, the weed scores in 2006 were more strongly associated with that year’s water conditions than with the weed seedbank size.

Full article
 
keyword:
Cambodia, direct seeding, irrigation rehabilitation, rain-fed lowland rice.

Abstract
Weed infestations are a major cause of yield reduction in rice (Oryza sativa) cultivation, particu-larly with direct-seeding methods, but the relationship between weed dynamics and wateravailability in Cambodian paddy fields has not been documented previously.We surveyed theweed abundance and weed seed banks in the soil of paddy fields with inferred differences intheir water regime in 22 farm fields in three provinces of Cambodia in the 2005 and 2006 rainy seasons.We studied rainfed lowland fields in upslope and downslope topographic positions andfields at different distances from the irrigation water source inside an irrigation rehabilitation area.The weed seed banks were estimated by seedling emergence in small containers and weedabundance and vigor were estimated by a simple scoring system.The estimated weed seed bankin the top 5 cm of soil ranged from 52.1 to 167 * 103 seeds m-2 (overall mean of 8.5 * 103 seeds m-2) and contained a high proportion (86%) of sedge species, such as Fimbristylis miliacea L. and Cyperus difformis. Several fields had particularly large seed banks, including one near the reservoir. No clear difference was found in the weed seed banks between the irrigated fields thatwere located close to (upstream) and distant from (downstream) the water source or betweenthe irrigated and rain-fed lowland fields, but the weed scores were larger in the rain-fed fieldsand the downstream fields within the irrigated area. A water shortage during the late growingseason in 2005 led to a proliferation of weeds in some fields and an associated increase in weedseedbank size in 2006. However, the weed scores in 2006 were more strongly associated with that year’s water conditions than with the weed seedbank size.

Full article
 
Title:
APPLYING SIMULATION TO IMPROVE RICE VARIETIES IN REDUCING THE ON-FARM YIELD GAP IN CAMBODIAN LOWLAND RICE ECOSYSTEMS, by P. L. POULTON, T. VESNA, N. P. DALGLIESH, V. SENG, Volume 51, Issue 2 April 2015, pp. 264-284
Description:

Abstract

Achieving export growth in rice production from variable rainfed lowland rice ecosystems is at risk if depending on conventional breeding or genetic development alone. Sustained, long-term production requires building adaption capacity of smallholder farmers to better manage the challenges of seasonal climate variability and future climate change. Better understanding of the risks and constraints that farmers face in managing their current cropping system helps develop strategies for improving rice production in Cambodia. System models are now considered valuable assessment tools for evaluating cropping systems performance worldwide but require validation at the local level. This paper presents an evaluation of the APSIM-Oryza model for 15 Cambodian rice varieties under recommended practice. Data from a field experiment in 2011, conducted in a non-limiting water and nutrient environment, are used to calibrate varietal-specific coefficients and model input parameters. An independent dataset is then used to validate the model performance for a ‘real-world’ situation using on-farm data for six rice varieties planted in 54 farmer fields on 32 farms in two villages of Southeastern Cambodia. From this analysis, the APSIM-Oryza model is shown to be an acceptable tool for exploring the mismatch between current on-farm yields and potential production through yield gap analysis and the exploration of cropping system options for smallholder farmers to increase production, adapt to seasonal climate variability and be prepared for potential climate changes.

Full article
 

keyword:
N/A

Abstract

Achieving export growth in rice production from variable rainfed lowland rice ecosystems is at risk if depending on conventional breeding or genetic development alone. Sustained, long-term production requires building adaption capacity of smallholder farmers to better manage the challenges of seasonal climate variability and future climate change. Better understanding of the risks and constraints that farmers face in managing their current cropping system helps develop strategies for improving rice production in Cambodia. System models are now considered valuable assessment tools for evaluating cropping systems performance worldwide but require validation at the local level. This paper presents an evaluation of the APSIM-Oryza model for 15 Cambodian rice varieties under recommended practice. Data from a field experiment in 2011, conducted in a non-limiting water and nutrient environment, are used to calibrate varietal-specific coefficients and model input parameters. An independent dataset is then used to validate the model performance for a ‘real-world’ situation using on-farm data for six rice varieties planted in 54 farmer fields on 32 farms in two villages of Southeastern Cambodia. From this analysis, the APSIM-Oryza model is shown to be an acceptable tool for exploring the mismatch between current on-farm yields and potential production through yield gap analysis and the exploration of cropping system options for smallholder farmers to increase production, adapt to seasonal climate variability and be prepared for potential climate changes.

Full article
 

Title:
Farmers’ Management Practices and Grain Yield of Rice in Response to Different Water Environments in Kamping Puoy Irrigation Rehabilitation Area in Northwest Cambodia, by Yen Thi Bich Nguyen, Akihiko Kamoshita, Yuji Araki & Makara Ouk, Volume 14, 2011 - Issue 4
Description:

Abstract

The farmers’ management practices and grain yield were examined in the consecutive 4 cropping seasons from wet season rice (WSR) in 2008 to dry season rice (DSR) in 2010 across upstream, midstream and downstream fields, along two secondary drainage canals (located either upstream or downstream side along the main canal) in the Kamping Puoy Irrigation Rehabilitation area (KPIR). In WSR, standing water depth was much deeper in downstream fields where medium and late maturing varieties were planted from May than in upstream fields where early and early medium maturing varieties were planted later (mostly in July and August). In DSR there was less difference in water conditions between upstream and downstream fields and variation in planting and harvesting time was small. As the area percentage of fields where DSR was introduced increased from 2008 (54%) to 2010 (100%), planting time in WSR was later (e.g., from May to July) with declining proportion of dry seeding method and mid-season tillage. Grain yield was low in DSR, particularly in 2010 (287 and 247 g m-2 in 2009 and 2010 on average, respectively), due to insufficient weed control and small amount of fertilizer, and the yield was lowest in fields which practiced DSR for the first time. Grain yield in WSR (286 and 291 g m-2 in 2008 and 2009 respectively) increased by transplanting, use of high yielding Raing Chey variety, and application of a larger amount of N chemical fertilizer. These findings indicated that the agriculture extension support to farmers, particularly in DSR, is a key important factor for rice yield improvement in KPIR.

Full article

keyword:
Cambodia, Double cropping, Irrigation rehabilitation, Rice, Water distribution

Abstract

The farmers’ management practices and grain yield were examined in the consecutive 4 cropping seasons from wet season rice (WSR) in 2008 to dry season rice (DSR) in 2010 across upstream, midstream and downstream fields, along two secondary drainage canals (located either upstream or downstream side along the main canal) in the Kamping Puoy Irrigation Rehabilitation area (KPIR). In WSR, standing water depth was much deeper in downstream fields where medium and late maturing varieties were planted from May than in upstream fields where early and early medium maturing varieties were planted later (mostly in July and August). In DSR there was less difference in water conditions between upstream and downstream fields and variation in planting and harvesting time was small. As the area percentage of fields where DSR was introduced increased from 2008 (54%) to 2010 (100%), planting time in WSR was later (e.g., from May to July) with declining proportion of dry seeding method and mid-season tillage. Grain yield was low in DSR, particularly in 2010 (287 and 247 g m-2 in 2009 and 2010 on average, respectively), due to insufficient weed control and small amount of fertilizer, and the yield was lowest in fields which practiced DSR for the first time. Grain yield in WSR (286 and 291 g m-2 in 2008 and 2009 respectively) increased by transplanting, use of high yielding Raing Chey variety, and application of a larger amount of N chemical fertilizer. These findings indicated that the agriculture extension support to farmers, particularly in DSR, is a key important factor for rice yield improvement in KPIR.

Full article

Title:
Field level damage of deepwater rice by the 2011 Southeast Asian Flood in a flood plain of Tonle Sap Lake, Northwest Cambodia, by Akihiko Kamoshita • Makara Ouk, Paddy Water Environ (2015) 13:455–463
Description:
Abstract
The 2011 flood damaged about 11 % of planting area in Cambodia, but the damaged proportion reached 30 % in Sangke district, Battambang province, located in the flood plains of Tonle Sap Lake. The aim of this study was to characterize completely damaged deepwater rice production due to the flood along the transect from the town-side shallower fields to the lake-side deeper fields. The flooding water from Tonle Sap Lake rose with 7 cm/day in September and October in the deeper fields where floating rice was grown and 8–10 cm/day in October in the shallower fields where lowland rice was grown. The maximum water was recorded on 16 October with 3.2 and 2.0 m at the deepest and shallowest edge fields. The area was characterized as flatness with only 1.2 m elevation differences in 4.3 km distance along the transect. The flooding water took 13.7 h for approaching 100 m distance. Complete recession of flood water was end of November at the shallow edge and at late December in the deep edge in 2011. The flooding duration deeper than 50 cm was 2.5 month and nearly 3 months in the middle zone and deeper floating rice area, respectively. The complete submergence started first in some fields in the middle zone on 12 September, followed by the shallower lowland rice area, and finally in the deep floating rice area by 1 October.

Full article


keyword:
Floating rice ; Flood damage ; Flood-prone rice ; Rice ecosystem ; Tonle Sap Lake
Abstract
The 2011 flood damaged about 11 % of planting area in Cambodia, but the damaged proportion reached 30 % in Sangke district, Battambang province, located in the flood plains of Tonle Sap Lake. The aim of this study was to characterize completely damaged deepwater rice production due to the flood along the transect from the town-side shallower fields to the lake-side deeper fields. The flooding water from Tonle Sap Lake rose with 7 cm/day in September and October in the deeper fields where floating rice was grown and 8–10 cm/day in October in the shallower fields where lowland rice was grown. The maximum water was recorded on 16 October with 3.2 and 2.0 m at the deepest and shallowest edge fields. The area was characterized as flatness with only 1.2 m elevation differences in 4.3 km distance along the transect. The flooding water took 13.7 h for approaching 100 m distance. Complete recession of flood water was end of November at the shallow edge and at late December in the deep edge in 2011. The flooding duration deeper than 50 cm was 2.5 month and nearly 3 months in the middle zone and deeper floating rice area, respectively. The complete submergence started first in some fields in the middle zone on 12 September, followed by the shallower lowland rice area, and finally in the deep floating rice area by 1 October.

Full article


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