The monsoon from the southwest and the mountains in central north and east delineate the climatic zones in Sri Lanka. Mean annual rainfall is less than 900 mm in the south-eastern and north-western dry areas of the island. It reaches over 5000 mm in the western slopes and the central highlands. This monitoring period covers the growing and harvesting season within the main season (Maha) from January to March, both for rice and maize, as well as the early sowing season for crops within the second season (Yala) during April. According to the CropWatch monitoring results, crop conditions were slightly below, but close to average for the whole period.

Influenced by monsoon and topography, the country experienced cold and dry windy weather during January and February, followed by a rainy period from March to April. Compared to 15YA level, precipitation (RAIN -58%) experienced a steep decline, while temperature and radiation both increased (TEMP +0.7℃, RADPAR +7%). The reduction in rainfall mainly happened in February. The fraction of cropped arable land (CALF) remained comparable to 5YA. BIOMSS was up 1% as compared to 15YA. As shown on the NDVI development graph, NDVI values were near average during January and showed a slight decrease to below average levels in March. The values then recovered to the 5YA in April. The below-average NDVI values can be attributed to the large reduction of rainfall in February, which led to insufficient water supply for the crops. However, dry conditions during the harvesting period have little influence on yield. The maximum VCI for the whole country was 0.95.

As shown by NDVI clusters map and profiles, spatial heterogeneity of crop condition was significant throughout the country's cropland. Only 14.3% of cropland showed consistent above-zero NDVI departure values for the entire period, including the area between Anuradhapura and Puttalam and scattered areas in Eastern and Uva Provinces. The other croplands almost showed negative NDVI departure values to different extents for the whole period except for January. These croplands were mainly distributed in Provinces of North Western, western of North Central, Uva and coastal areas. The VCIx map exhibited similar patterns as the NDVI clusters map.

Regional analysis

Based on the cropping system, climatic zones and topographic conditions, three sub-national agroecological regions can be distinguished for Sri Lanka. They are the Dry zone, the Wet zone, and the Intermediate zone.

In the Dry zone, the recorded RAIN (197mm) was 58% below average and amounted to less than 2 mm per day, which was insufficient for the growth of maize in this region. TEMP was 0.6°C above average with RADPAR up as well, by 7%; BIOMSS decreased by 3% compared to average. CALF was the same as the 5YA level (100%) and cropland was fully utilized. NDVI followed a similar trend as the whole county. The VCIx for the zone was 0.94. Overall, crop conditions were below-average due to the shortage of rainfall.

The Wet zone went through the first rainy season during March and April.  RAIN (352mm) was 57% down compared to 15YA. TEMP (+0.9°C) and RADPAR (+9%) were higher. For BIOMSS, a 10% rise was recorded and cropland was fully utilized as usual. NDVI was near average for the whole period. The VCIx value for the zone was 0.93. Crop conditions were fair for this zone and a bit better than for the other two sub-national regions.

The Intermediate zone also experienced dry conditions with RAIN at 280 mm, 59% below 15YA. Less than 3mm precipitation per day could not meet the need of water for rice and maize. TEMP and RADPAR were up 0.6°C and up 8% above average respectively. With full use of cropland, BIOMSS was 3% above average. The variation of NDVI was analogous to the Dry zone. The VCIx value for the zone was 0.96. The condition of crop was assessed as slightly below-average.

Figure 3.21. Sri Lanka crop condition, January 2020 - April 2020

(a) Phenology of major crops

(b) Crop condition development graph based on NDVI

(c) Rainfall profile

(d) Temperature profile

(e) Maximum VCI

(f) Spatial NDVI patterns compared to 5YA (g) NDVI profiles

(h) Crop condition development graph based on NDVI (Dry zone (left) and Wet zone (right))

(i) Crop condition development graph based on NDVI (Intermediate zone)

Table 3.50. Sri Lanka agroclimatic indicators by sub-national regions, current season's values and departure from 15YA, January 2020 - April 2020

Table 3.51. Sri Lanka agronomic indicators by sub-national regions, current season's values and departure from 5YA, January 2020 - April 2020