Rice production of Cambodia, Thailand and Vietnam increased by 320 thousand tons. Drought in the lower Mekong river had only adversely affected dry season rice production and had limited impacts on rice supply
Monitoring results from Chinese Academy of Sciences
In order to monitor the impact of drought on rice production in the lower Mekong River Basin, the CropWatch team from the Aerospace Information Research Institute, Chinese Academy of Sciences (AIRCAS) has carried an integrated monitoring and assessment of the growth condition and production of rice in Cambodia, Thailand and Vietnam together with field survey data. For this purpose, it has also used multi-source optical and SAR satellite imageries including Sentinel-1, Sentinel-2, Landsat 8 and Moderate Resolution Imaging Spectroradiometer (MODIS) from September 2019 to mid-April 2020. The specific research results are as follows:
The total rice production in Cambodia, Thailand and Vietnam harvested during September 2019 to April 2020 or to be harvested is estimated to be up by 320 thousand tons. The drought, which occurred in February and March 2020 mainly, had slight impacts on rice growth during the dry season. The production of rainy season rice harvested before February 2020 increased 17% compared to the same period of last year. Considering rice production in last three years, the rice supply of the three countries decreased only by 1%, with a limited impact on their rice exports.
The growth condition of rainy season rice in Cambodia, Thailand and Vietnam in 2019-2020 was generally above the previous five years average (5YA) except for the scattered areas of Kampong Cham and Siem Reap Provinces in Cambodia where rice condition was below the 5YA. In contrast, the rice development during dry season was overall inferior to the average level, among which the growth of rice in western and northwest Thailand, Eastern, northern and southwest Cambodia, the southern and southwest coastal areas of Vietnam were significantly below the 5YA (Figure 1).
Figure 1. Rice growth condition in Cambodia, Thailand and Vietnam during the rainy season (left) and dry season (right) in 2019-2020
Among the three countries, rice in Vietnam outperformed that of Thailand and Cambodia, with about 85% of rainy season rice in an above-average condition. It is also noteworthy that 16% of the rainy season rice achieved the best condition over the last five years. Meanwhile, about two-thirds of dry season rice presented above-average condition. As for Cambodia, rice growth condition during rainy season was in general favorable, and about 75% of the rainy season rice was in an above-average situation. However, the dry season rice suffered from drought stress with only 29% of the rice area reaching the average level. Similarly, an above-average rice growth condition was also observed during rainy season in Thailand, accounting for 78% of rainy season rice area. However, rice development in dry season was hampered by severe drought with more than half of rice in a below-average condition.
Figure 2. Statistical analysis of different categories of rice growth condition during rainy and dry seasons in Cambodia, Thailand and Vietnam in 2019-2020.
Artificial Intelligence algorithms were applied to estimate the cultivated area of dry and rainy season rice from October 2019 to April 2020 in Cambodia, Thailand and Vietnam. The total rice area was estimated at 12,225 thousand hectares, up by 6% compared with the same period last year. The cultivated area of rainy season rice in Cambodia, Thailand and Vietnam increased by 5%, 24% and 8%, respectively. However, the rice area in dry season in the three countries decreased by 23%, 4% and 9% respectively as affected by the severe drought.
Remote sensing-based model revealed that the yield of rainy season rice in Cambodia and Thailand increased by 5% and 3% respectively while it remained at same level as the previous season in Vietnam. The rainy season rice production in the three countries increased by 10%, 28% and 8% respectively compared to the same period last year. Their total production of rainy season rice since mid-October 2019 reached 27.22 million tons, with a year-on-year increase of 4.05 million tons (or +17%).
Dry season rice was severely affected by drought although most rice are irrigated. The dry season rice yield in Cambodia, Thailand and Vietnam dropped by 8%, 12% and 1% year-on-year (YoY), respectively, and the production fell by 30%, 15% and 10% respectively. In total the dry season rice production of the three countries was only 19.99 million tons, a decrease of 3.73 million tons or 16%, compared with the same period last year.
Consequently, the total output of rice harvested or to be harvested in rainy season and dry season from October 2019 to April 2020 was estimated at 47.21 million tons, an increase of 1% or 0.32 million tons.
As for each country, Vietnam was less affected by the drought. From mid-October 2019, the total output of rice harvested or to be harvested in Vietnam was 14.84 million tons, a slight decrease of 3% from the same period of last year. Cambodia was the most affected country, with the total output of rice of 9.55 million tons, a decrease of 5% from the same period of last year. A large increase in rice production during the rainy season (major rice) in Thailand more than compensated the loss of dry season rice caused by the drought. Rice production of Thailand increased by 1.24 million tons.
Considering the overall stable rice production during the past three years in Cambodia, Thailand and Vietnam, the drought-induced loss of dry season rice over February to March 2020 had limited impacts on the rice market and the total rice supply of the three countries only dropped by 1% year on year.
Table 1. Rainy and dry season rice production in Cambodia, Thailand and Vietnam
| Rice type | Country | Area | Yield | Production |
| 2019-2020 (thousand hectares) | Departure YoY (%) | 2019-2020 (Kg / ha) | Departure YoY（%） | 2019-2020 （million tons） | Departure YoY (%) |
| Rainy season rice | Cambodia | 1,834 | 5 | 3744 | 5 | 6.87 | 10 |
| Thailand | 4,821 | 24 | 2807 | 3 | 13.53 | 28 |
| Vietnam | 1,179 | 8 | 5786 | 0 | 6.82 | 8 |
| Subtotal | 7,834 | 16 | - | - | 27.22 | 17 |
| Dry season rice | Cambodia | 602 | -23 | 4448 | -8 | 2.68 | -30 |
| Thailand | 2,513 | -4 | 3696 | -12 | 9.29 | -15 |
| Vietnam | 1,276 | -9 | 6289 | -1 | 8.02 | -10 |
| Subtotal | 4,391 | -9 | - | - | 19.99 | -16 |
| Total | 12,225 | 6 | - | - | 47.21 | 1 |
Note: the rainy season rice in this report represents the rice whose sowing concentrated from early August to October 2019, and whose harvest concentrated from mid-October 2019 to early February 2020. Each country uses different terminology to name the rainy season rice. For example, it is named as major rice in Thailand, median rice and late rice in Cambodia, and winter-spring rice in southern Vietnam. The dry season rice in the report is a general term for the rice whose sowing period was from late November 2019 to early January 2020, and harvest period was from late March 2020 to late April 2020.
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