The period from July to October is the rainy season in Cambodia. The floating rice, medium rice and late rice were sown in July. The soybeans began to mature in early July as well and the harvest of rainy-season maize and rainfed rice began in August and September, respectively.

The weather in Cambodia during this monitoring period was wetter than in the past. The precipitation (RAIN) in Cambodia was 14% higher, while average temperature (TEMP) and radiation (RADPAR) were close to average. The wetter weather was generally favorable for crop growth and thus potential biomass (BIOMSS) was about 1% higher than average. However, the stronger rainy season posed difficulties for crop growth monitoring based on satellite remote sensing, as manifested by cloud cover obscuring satellite images. It introduced excessive noise into the synthetic NDVI time series curves, thus affecting the determination of crop growth. However, with the help of the maximum vegetation condition index distribution map, it can be found that the VCIx value is higher than 0.8 in most areas, which indicates that the crop growth is normal in general, and only some areas have poor crop growth. The NDVI spatial clustering map also shows that the crop condition of about 7.8% of the cultivated land (orange areas) has been deteriorating since mid-July, mainly in Banteay Meanchey and Siem Reap provinces on the north side of Tonle Sap Lake and Kampong Thom and Kampong Cham provinces in the east. About 27.8% of the cultivated land (red areas) had poor crop growth in July, which gradually returned to normal after August. These areas are mainly concentrated in Prey Veng, Svay Rieng and Kampong Cham provinces in the lower Mekong River. In the rest of the cultivated land (light green, dark green and blue), the NDVI of the crops remained around the average level and the crop growth was normal.

In conclusion, a combination of various agroclimatic indicators shows that the crop growth in Cambodia during this monitoring period was normal.

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.

According to agroclimatic indicators, the precipitation (RAIN) in the Tonle-Sap region (agroecological subzone 117) was significantly higher by 20% than the average, while the temperature (TEMP) decreased by about 0.3°C, radiation (RADPAR) decreased by about 3%, and potential biomass (BIOMSS) was 1% higher. The synthetic NDVI time series curves in this area were more volatile and overall lower than average due to the influence of cloud cover on the satellite images, but this does not reflect the true crop growth. According to the distribution map of the maximum vegetation condition index, the VCIx value was higher than 0.8 in all areas of the district, except for some areas in the north and west, where the crop growth was poor, indicating that the overall crop growth in the district was normal.

The Mekong Valley region (agroecological subzone 118)  is the main agricultural area in Cambodia. The precipitation (RAIN) in this region was significantly higher by 20%, temperature  (TEMP) was lower by 0.1°C, and both radiation (RADPAR) and potential biomass (BIOMSS) were higher by 2%. According to the precipitation time series figure, the above-average precipitation was mainly concentrated in mid- and late July, late August and early October, and this almost coincided with the occurrence of the minimal value points of the NDVI time series curve, indicating that precipitation and cloud cover limited the remote sensing monitoring of crop growth in the region. Although the distribution map of the VCIx shows that many areas in the region had crop VCIx less than 0.8, the spatial clustering map of the distance level shows that the NDVI of cropland crops in the central and western parts of the region (light green and blue areas) remained basically at the average level. While the NDVI of crops in the eastern region (red area) was below the average level until August, it gradually recovered afterwards. The NDVI of crops in only some areas in the northeast (orange area) kept decreasing, but the area was not large. Therefore, the crop growth in the region was basically normal or slightly below average.

For the Northern Plain and Northeast region (agroecological subzone 119) , the region had a 7% higher precipitation (RAIN), 0.1°C lower temperature (TEMP), 3% higher radiation (RADPAR), and 1% higher potential biomass (BIOMSS). Although the NDVI time series curves of crops in this area remained consistently below average, the VCIx value of this region was as high as 0.92, and the spatial distribution of VCIx also shows that the VCIx in most areas of this region was higher than 0.8, indicating that the crops in this area were basically growing normally.

The precipitation (RAIN) in the southwestern Hilly region (agroecological subzone 120)  was significantly higher than the average by 25%, the temperature (TEMP) was lower by about 0.5°C, the radiation (RADPAR) was significantly lower by 8%, and the potential biomass (BIOMSS) was lower by about 2%. The VCIx index of the region was as high as 0.91, and the spatial distribution of the VCIx also indicates that the crop growth in the region was basically normal.

Figure 3.26 Cambodia's crop condition, July - October 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 region

(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 region

(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, July- October, 2022

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