B002-0025
Assessing the Impacts of Changing Hydrology, Climate, and Agronomic Practices to Dry Season Rice Production in the Tonle Sap Floodplains

Monday, 7 December 2020
Poster
Manuel Marcaida III, Student, School of Environmental and Forest Sciences, Seattle, WA, United States, Yasmine Ali Farhat, University of Washington Seattle Campus, Civil and Environmental Engineering, Seattle, United States, Faisal Hossain, University of Washington, Seattle, WA, USA, Seattle, United States, Rebecca Bergquist Neumann, University of Washington, Seattle, WA, United States and Soo-Hyung Kim, University of Washington, School of Environmental and Forest Sciences, Center for Urban Horticulture, Seattle, United States
Abstract:
The majority of rice production in Cambodia happens in the Tonle Sap floodplains, where irrigation and nutrient-rich sediments are delivered by the Mekong River every monsoon season. With the increasing presence of hydropower dams in the recent decade, the intensity and extent of floodwater has changed. Irrigation has become more accessible during the dry season, which has opened up more areas for rice cultivation, but the nutrient quality of the sediments is expected to decline. Moreover, drought is becoming a frequent occurrence and average temperature is increasing. This study examined how dry-season rice cultivation in the Tonle Sap floodplains is impacted by hydrological changes, climate, and agronomic practices.

We focused on Kampong Thom, a major rice-producing province located within the Tonle Sap floodplain. Spatio-temporal and yield changes in rice production were estimated using remote sensing and crop modeling. Time-series satellite images from 2001 to 2019 were used to determine the pixel-based changes in location and timing of cultivation following the PhenoRice algorithm. Yield simulations to determine the effect of hydrology, agronomic practices, and increasing temperatures were performed using the ORYZA (v3) Rice Model, validated by actual field observations.

Results indicated that rice areas increased with lake extent during the dry season. In addition, cropping areas were shifted and the timing of crop establishment was modified. Simulations predicted that yield penalty was greater than the yield gained when soil organic carbon was decreased than when it was increased. We also determined the optimum amount of nitrogen required and efficient timing of applications to get the maximum attainable yield. Increased temperature decreased yield and even greater loss occurred when average temperature increased by more than 2°C. This study provides information on rice production and yield changes in the Tonle Sap floodplains as farmers face the challenges of changing hydrology and climate.

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