The wet season in Cambodia usually lasts from May to October. Within this monitoring period, the Early Rice (dry season) and Dry Season Maize were harvested in the end of April. The beginning of the wet season governs the planting of the wide variety of rice that is grown in this country.  Wet Season Maize and Early Season Rice are planted in May, followed by Floating Rice and Medium Rice. Wet Season Maize reached silking by the end of this monitoring period. Soybean reached maturity by late July. 

Figure 3.26 Cambodia’s crop condition, April - July 2020

Figure 1: Phenology of major crops

The overall rainfall in this period was less than the average (RAIN -19%) while the temperature was 0.8 ºC above the 15YA. The rainfall deficit was mainly due to below-average rainfall in April, May and early June. It subsequently reached average levels. The drought conditions were exacerbated by the prolonged record low water levels of the Mekong River. The inflow of water from the Mekong River into the Tonle Sap Lake usually starts in May. This year, the reversed flow has not yet started as of August 3, 2020. The RADPAR was 4% above the 15YA. Estimated biomass for the country was 5% above the 15YA, but it was 2% below the 15YA for the important Tonle Sap Lake region. 

Figure 2: the rainfall departure compared to 15YA

 Figure 3: rainfall time series from Aprl to July, 2020

 Figure 4: temperature time series from Aprl to July, 2020

Figure 5: Photosynthetically Active Radiation (PAR) time series from April to July, 2020

Figure 6: Biomass accumulation potential (BIOMSS)

The crop condition development graph based on NDVI for Cambodia reveals the poor crop conditions during the period from April to June. Conditions improved to average in July. VCIx nationwide reached 0.88. It varied greatly within the regions.  The NDVI development curve stayed below the trend of the 15YA until the end of June. This is probably due to the delayed planting of Early Rice and Floating Rice. The NDVI departure clustering map and its development profiles reveal the noticeable changes of crop condition across regions and time. There are two main remarkable areas where the NDVI departure across the period was significant: As shown in Figure 8, the blue area has excellent crop conditions (12.8% of the area), where the NDVI departure was above the average and shows an increasing trend. The red and orange color region (36.7%) represents poor crop conditions.

Figure 7: NDVI development profiles(left) and Maximum Vegetation Condition Index (VCIx)(right)

 Figure 8: NDVI departure clustering map and its development profile

The proportion of NDVI anomaly categories also shows the noticeable changes of crop conditions. It reveals that  25% of cropped land was below or slightly below average, while 30% of cropped land was above or slightly above the average. As seen in Figure 9, cropped land with poor conditions was mainly distributed around the Tonle Sap region and the southern part of the Mekong valley. The cropped land with above average crop conditions was mainly distributed in the eastern part of the Mekong Valley.

Figure 9: Proportion of NDVI anomaly categories compared with 5YAand the NDVI departure pictures

Drought conditions caused a delay in planting in May and slow crop development. Conditions returned to average by the end of July. It remains to be seen whether farmers were able to fully overcome the challenges posed by the lack of water and whether this will have an impact on rice production in Cambodia. 

Regional Analysis:

Tonle-Sap region:

This region is mostly flat and is the main rice production region of Cambodia. The rainfall was 13% below average, temperature was 0.9℃above average and RADPAR was near average compared to the 15YA. Serious rainfall deficits occurred in April and May. The NDVI development profile reflects the impact of lack of rainfall and lack of water inflow from the Mekong River into the lake region. NDVI was far below the 5YA until mid June, but reached above-average levels by late July. During this period, 90% of arable land was cropped and the fraction of cropped land was only 1% below the average compared to the 5YA.

Figure 10: The NDVI profile for Tonle-Sap region

Northern Plain and Northeast:

This region is an area of hilly highland and mountains such as the Dangrek Mountains. It is mostly covered by forest and some major crops such as rubber, cassava, cashew nuts and avocado. During this period, the rainfall was 25% below the average while the temperature (+0.8°C) and RADPAR (+7%) were above the 15YA. Due to the serious deficit of rainfall in this monitoring period, crop conditions were below average as indicated by NDVI development profile. CALF was high, at 99%.

Figure 11: The NDVI profile for Northern Plain and Northeast

Mekong valley between Tonle-sap and Vietnam border:

This region mainly includes the Mekong Delta along the river. The area is generally flat and the major crop is rice. The rainfall was 14% below the average while temperature and RADPAR were 0.8°C and 2% above the 15YA. According to the NDVI development graph, the crop conditions were below the 5YA from April to the middle of June and recovered to last year’s level by the end of July. During this period, 89% of arable land was cropped, near the 5YA.

Figure 12: The NDVI profile for Mekong valley between Tonle-sap and Vietnam border

SouthWest Hilly region:

This region contains a range of hills and mountains with forests that cover the Cardamom and Elephant Mountains. Various crops are grown, spices (pepper) and fruits (durian). The rainfall was 16% below average, while temperature (+ 0.8℃) and RADPAR (+6%) were above the 15YA. Due to the significant increase of RADPAR, the potential biomass was 7% above the 15YA. The NDVI development profile in this region indicates that crop conditions were generally below the 5YA, while they recovered to the 5YA by the end of July. 

Figure 13: The NDVI profile for SouthWest Hilly region

Table 3.43 Cambodia’s agroclimatic indicators by sub-national regions, current season’s values and departure from 15YA, April - July 2020

Table 3.44 Cambodia’s agronomic indicators by sub-national regions, current season’s values and departure from 5YA, April - July 2020

Table 2: CAlF and VCIx table