Cambodia has gradually entered the dry season starting in November, when the harvest of wet-season early rice was ended and the sowing of dry-season early rice began subsequently. Moreover, the sowing of dry season maize and soybean was over in December, after that started the harvest of medium rice, late rice and floating rice in January.

During this monitoring period, Cambodia experienced wetter and relatively cooler weather conditions. Compared to the same period in the past, the precipitation in Cambodia was 12% higher (RAIN), while the average temperature was slightly cooler by 0.2°C (TEMP) and the radiation was basically close to average (RADPAR). The relatively abundant rainfall resulted in a 3% higher potential biomass than average (BIOMSS), however, NDVI profile for the country shows that crop growth condition was consistently below average during the monitoring period. The time series graph of precipitation shows that the excess precipitation was mainly due to above-average precipitation in mid-late October, mid-November and late December. The above-average precipitation in mid-late October mainly coming from the impact of the 18^th Typhoon KOMPASU, while the accumulated precipitation in mid-October and late December both reached their respective highest levels in the past 15 years. Considering that the gap between actual crop growth condition and average level did not start to decrease until late December, this indicates that the increased precipitation in October and November did not contribute significantly to the growth of crops in the rainy season, and may even have caused damage to crops in the form of short duration heavy precipitation, while the increased precipitation in late December effectively alleviated the insufficiency of rainfall in the dry season and improved the crop growth condition, narrowing the gap between the actual crop growth condition and the average level. The spatial NDVI patterns show that the low NDVI in October was mainly caused by the negative NDVI deviation appearing in the light green area (about 24.2%) in early October and in the red area (about 9.2%) in late October, and these two negative deviations are most likely caused by the cloud cover on the satellite images. In addition, the below-average NDVI appearing in orange area (about 6%) and red area (except for late October) may be caused by moisture deficit due to uneven precipitation distribution. In addition, the record low flow levels of the Mekong River, which have persisted over the last 3 years, are negatively impacting the production potential, mainly in the important Tonle Sap Lake region. Considering that the VCIx value at the national scale was as high as 0.88 and the CALF index fell slightly by about 1%, the estimated production in the country is below average.

Regional analysis

Based on cropping systems, climatic zones and topographic conditions, four sub-national regions are described below: The Tonle Sap Lake area, a seasonally inundated freshwater lake which is influenced by the inflow and outflow from the Mekong River, 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 Tonle Sap Lake area, the region experienced an 8% higher cumulative precipitation (RAIN), 0.2°C lower average temperature (TEMP), and about 1% lower radiation (RADPAR), resulting in about 2% higher potential biomass (BIOMSS). However, the NDVI of crops in this region was below average until late December, and the low NDVI was mainly caused by the negative NDVI deviation that occurred in southeastern Banteay Meanchey (orange area), eastern Pursat and western Kampong Thom (red area). In addition, the CALF index in this region was as high as 98% and the VCIx value was 0.89. However, the below average NDVI trajectory indicates slightly below average production levels.

For Mekong Valley zone, the precipitation in this zone was significantly higher by 18% (RAIN), the average temperature was about 0.2°C lower (TEMP), radiation was near average (RADPAR), and abundant precipitation resulted in a higher potential biomass (BIOMSS, +2%). Similar to the Tonle Sap Lake zone, NDVI in this zone was likewise below average until late December and then gradually approached average levels. Although the Mekong Valley zone has a high CALF index of 95% and an VCIx index of 0.87， the crop production in this zone is predicted to be sightly below average as well.

For northern plains and northwest, the zone had an 8% higher cumulative precipitation (RAIN), about 0.2°C lower average temperature (TEMP), and about 1% higher radiation (RADPAR), resulting in a potential biomass bias of about 3% (BIOMSS). Crop NDVI in the zone was below the average by about 0.1 in early October, and then was close to the average. The CALF index in the zone reached at 99% and the VCIx value was at 0.92, so the crop production in the zone is estimated to be fair.

For southwestern hilly region, the precipitation in this region was 12% above average (RAIN), the average temperature was about 0.2°C lower (TEMP), and the radiation was about 3% lower (RADPAR), resulting in a potential biomass in this region that was also about 2% higher (BIOMSS). In terms of the NDVI profile in this zone, the NDVI was significantly lower than average in the early October and then quickly rose close to average. Therefore, the decrease in NDVI was presumeably due to cloud cover on the satellite images. Thereafter, the NDVI decreased slightly, but quickly recovered to the average level. Meanwhile, the CALF index in this area is as high as 99% and the VCIx index is close to 0.91, so the crop production in this area is predicted to be close to the average.

Figure 3.26 Cambodia’s crop condition, October 2021- January 2022

(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) Time series temperature profile (left) and rainfall profile (right)

(g) Crop condition development graph based on NDVI (left) and time series rainfall profile (right) in Tonle Sap Lake area

(h) Crop condition development graph based on NDVI (left) and time series rainfall profile (right) in Mekong valley region

(i) Crop condition development graph based on NDVI (left) and time series rainfall profile (right) in Northern plain and northeast zone

(j) Crop condition development graph based on NDVI (left) and time series rainfall profile (right) in Southwest hilly region

Table 3.41 Cambodia's agro-climatic indicators by sub-national regions, current season's values and departure from 15YA, October 2021- January 2022

Table 3.42 Cambodia's agronomic indicators by sub-national regions, current season's values and departure from 5YA, October 2021- January 2022