Evaluating the impacts of drought on rice productivity over Cambodia in the Lower Mekong Basin

Fertilizer application rates for the study period (2000–2016) compared with annual rice yields over Cambodia.

Abstract

Recurring drought in the Lower Mekong countries has inflicted enormous pressure on the natural ecosystem, agricultural productivity, and water resources. We implemented a comprehensive drought and crop yield information system, the Regional Hydrologic Extremes Assessment System (RHEAS) that couples a core hydrologic model with a crop growth model, over Cambodia in the Lower Mekong Basin (LMB) to capture the subtle, intrinsic nature of drought, and assess the impact on inter-seasonal and intra- annual rice yields. Simulations based on RHEAS show good agreement with observations (R2 ~ 0.8). A regional scale assessment over Cambodia was carried out to examine linkages between rice productivity and meteorological/hydrologic drought variability from 2000-2016. Using standardized indices of drought and other indicators of meteorological, agricultural, and hydrologic drought, the onset and prevalence of dry and wet periods were examined at multiple temporal scales. The temporal variability in drought intensity exhibited higher stress, indicating mild to severe dry conditions, during the initial months (Mar-May). However, the onset of monsoon at the beginning of the planting season (June) resulted in the prevalence of normal to moderate wet conditions. A linear trend analysis for the period 2000 - 2016 showed a consistent increase (2900 kg/ha in 2000 to 3550 kg/ha in 2016) in rice yields, though drought- stricken provinces showed lower yields throughout the study period. Overall, a continuous increase in annual rice yields irrespective of the stress conditions was noted with no clear pattern linking drought parameters with crop yields on a regional scale. The application of chemical-based fertilizers has steadily increased over the years since 2008 and the consistent increase in rice yields correlated (R2=0.84) with increased fertilizer use. Information from the hydrologic and crop model components within RHEAS enables development of critical regional and local thresholds, reflecting the increasing levels of risk and vulnerability towards drought.

Publication
Journal of Hydrology
Kostas Andreadis
Kostas Andreadis
Assistant Professor