U017-06
Connections Between Floodplain Location and Soil Mineral Nutrition in the Tonle Sap Floodplain, Cambodia
Tuesday, 15 December 2020: 05:50
Yasmine Ali Farhat, University of Washington Seattle Campus, Civil and Environmental Engineering, Seattle, United States, Gordon William Holtgrieve, University of Washington Seattle Campus, School of Aquatic and Fishery Sciences, Seattle, WA, United States, Manuel Marcaida III, Student, School of Environmental and Forest Sciences, Seattle, WA, United States, Soo-Hyung Kim, University of Washington, School of Environmental and Forest Sciences, Center for Urban Horticulture, Seattle, United States and Rebecca Bergquist Neumann, University of Washington, Seattle, WA, United States
Abstract:
The Tonle Sap Lake in Cambodia is the largest freshwater lake in South-East Asia. It is surrounded by an annually inundated floodplain, vital for rice cultivation. The Cambodian economy and local diet is heavily reliant on domestic rice agriculture and roughly one third of annual rice production takes place in the five provinces surrounding the Tonle Sap Lake. Seasonal flooding in the Tonle Sap floodplain is controlled by monsoon rains in the larger Mekong River Basin, a water system which is rapidly changing due to extensive dam construction. Damming along the Mekong River is expected to induce changes in both seasonal flooding duration and sediment deposition, both of which can have notable impacts on soil chemistry, and therefore, rice production and quality. Changes in flooding duration can affect the bioavailability of certain metal micronutrients necessary for plant growth and yield, and changes in sediment deposition can impact nutrient loading, as sediments are often considered nutrient-rich.
We analyzed changes in surface soil metal concentrations using X-Ray Fluorescence (XRF), including both beneficial micronutrients and other geogenic metals. We sampled fields located inside and outside of the floodplain, as well as sites located along a natural flooding gradient. Overall, we found that surface soils in rice fields within the floodplain had higher metal concentrations than soils in rice fields outside of the floodplain. Floodplain fields closer to the lake, which are inundated for a longer period of time, tended to have greater metal concentrations in their surface soils than floodplain fields further from the lake. One of the metals we detected this trend for is zinc — a frequently limiting micronutrient essential for rice plant growth. The change in soil chemistry associated with Tonle Sap flooding patterns suggests that dam-induced changes which result in reduced flooding could reduce surface soil mineral nutrition, potentially hindering rice plant production. We are continuing to work to understand soil chemical contaminants concentrations and rice grain nutritional quality.
