The wet season in Cambodia usually lasts from May to October, which is the primary production period for the main crops. Within this monitoring period, the harvest of early rice (dry season) and dry season maize was completed in April and the maturation of soybean started in July. Early rice (wet season) and wet season maize started to be planted in May, followed by the floating rice and medium rice.

Cambodia generally experienced normal agro-climatic conditions compared to the past 15 years. As the agro-climate indicators show, the rainfall for the country was slightly higher than average (RAIN, +3%) and the temperature (TEMP) was about average. Moreover, the radiation was above average as well (RADPAR, +5%), which contributed to an above-average predicted biomass (BIOMSS, +6%). Cambodia had experienced several natural disasters during the monitoring period, including strong winds and heavy downpours in early May and heavy rain mixed with strong winds brought by the typhoon Cempaka in late July. The cropped arable land fractionwas slightly higher than average (CALF, +2%), and the maximum VCI value was at 0.88, which indicates the crop conditions were close to average.

According to the NDVI profile for the country, the initial NDVI values were lower than the average of the previous 15 years, which is inferred to be the consequence of the below-average precipitation in March and early April, and then they recovered to the average level in the early May with an increasing rainfall. However, the NDVI values began to decline in early July and remained below the average level, which may have been due to the impact of Cempaka. The spatial patterns of the NDVI profiles show that about 14.3% of crop land (shown by the dark green, mainly located in southwest of the Kampong Cham) had an NDVI that was around 0.1 below average during the whole reporting period. For about 17.7% of crop land (shown by the red color), the NDVI values were higher than average by more than 0.1 in May and June. This indicates that the soybean condition were favorable in Prey Veng.

Regional analysis

Based on cropping systems, climatic zones and topographic conditions, four sub-national regions are described below: The Tonle Sap Lake area where the seasonally inundated freshwater lake and especially temperature are influenced by the lake itself, the Mekong valley between Tonle Sap and Vietnam border, Northern plain and northeast, and the Southwest Hilly region along the Gulf of Thailand coast.

For the Tonle Sap Lake area, compared to the average condition, the rainfall was higher (RAIN, +4%) and the temperature was close to the average (TEMP, +0.1℃). In the meanwhile, the radiation increased above the average level (RADPAR, +4%). The agro-climatic conditions mentioned above were beneficial to the growth of the crops and thus the predicted biomass increased by 5% above the 15YA. According to the NDVI profile, NDVI values were close to the average of the past 5 years before mid-June,  when they started to drop slightly below the average.

As the main rice growing area of Cambodia, the Mekong valley between Tonle Sap and Vietnam border recorded a decreased precipitation (RAIN, -7%), near-average temperature (TEMP) and above-average radiation (RADPAR, +5%). As a result, the predicted biomass was higher than average by 6%. However, as shown by the NDVI profile, the NDVI values were lower than average after the mid-June, which was inferred to be caused by the delay of sowing of early wet-season rice.

The Northern plain and northeast experienced a wetter (RAIN, +9%) and slightly cooler (TEMP, -0.1℃) weather compared to the 15YA. The radiation for the region increased  (RADPAR, +7%), and the resulted biomass was predicted 8% higher than average (BIOMSS, +8%). The recorded NDVI values for the region was below average for the whole reporting period, especially in mid-May and late July, which is considered as the consequence of the strong winds and heavy downpours in May and the typhoon Cempaka in July.

For the region of Southwest Hilly, the precipitation was 2% higher than average (RAIN, +2%) , accompanied by near-average temperature (TEMP, +0.2℃) and above-average radiation (RADPAR, +3%), which resulted in an increase for biomass (BIOMSS, +4%). The cropped arable land fraction remained close to the average (CALF, 99%), and the maximum VCI for the region was at 0.91. However, the NDVI values for the region were slightly lower than average, which means the crop conditions for the region were near average. 

Figure 3.26 Cambodia’s crop condition, April-July 2021

(a) Phenology of major crops

(b) Crop condition development graph based on NDVI        (c) Maximum VCI

(d) Spatial NDVI patterns compared to 5YA           (e) NDVI profile

(f) Crop condition development graph based on NDVI_Tonle-sap (left) and NDVI_Mekong valley (right)

(g) Crop condition development graph based on NDVI (Northern plain and northeast (left), Southwest Hilly region (right))

(h) Time series temperature profile          (i) Time series rainfall profile

Table 3.43 Cambodia's agro-climatic indicators by sub-national regions, current season's values and departure from 15YA, April- July 2021

Table 3.44 Cambodia's agronomic indicataors by sub-national regions, current season's values and departure from 5YA, April - July 2021