This report covers the harvest of Second Season Rice in June. Planting of Main Season Rice started in May, while maize sowing started a bit earlier, in April.  Crop conditions during this reporting period were generally below the 5-year average (5YA) in April-June mainly due to the rainfall shortage in April and May.  However, by July, the crop conditions improved to close to the 5-year maximum, as indicated by the graph of NDVI development at the national level (figure 1.2).

The drier-than-normal weather Thailand has been experiencing gradually improved to close-to-average conditions.  Rainfall from April to July was recovering to just 7% below the 15YA (compared to -40% in the previous January – April period in 2020, or -23% for the same April-July period in 2019). Although the rainfall in May was significantly below last year's and the 15YA, it improved to close to the 15YA in July. According to provincial rainfall conditions, the deficit was more pronounced in some northern and central region provinces  (Chiang Rai, Phayao, Nan, Prae, Uttaradit, Phitsanulok, Kamphaeng Phet, Phichit, Nakorn Sawan, Uthai Thani, Chai Nat, Supanburi and Ang Thong), where the deficit exceeded 30% as compared to the 15YA. Also, the temperature (+0.7ºC) and radiation (+4%) were above average, which led to an increase in biomass production potential (BIOMSS) by 5%.

The spatial NDVI pattern (figure 1.5) shows that some patches in central and mostly north-eastern provinces, i.e., Ratchaburi, Kamphaeng Phet, Sakon Nakorn, Bueng Kan, Khon Kaen, Kalasin, Amnat Charoen, Ubon Ratchathani, Nakon Ratchasima, Surin, and Sri Sa Ket, have above-5YA crop conditions, covering 31.7% of total arable land. The crop conditions in the remaining areas stayed below average until early June. The areas in the north-eastern provinces having above-average crop conditions were also confirmed by the VCIx map.

Overall, considering the favorable national VCIx of 0.93, most provinces VCIx were higher than 0.8. Lowest values were observed for Sing Buri (0.67) and Ang Thong (0.64). Combined with a CALF of 99% which was 1% above average, the crops in the country recovered to mostly satisfactory conditions. 

The agricultural information is corroborated with several techniques such as a list frame survey, crop cutting experiments, forecasting and Geo-informatics. We compare the CropWatch indicators with the reports from regional offices and forecasting divisions and focus on rice only.

In 2020, the harvested area is forecasted to be up by 2.4% at the country level over the last year. The increase of rice harvested area and production is consistent with the increase in precipitation when compared with last year. In addition, the rice selling price is rather high, which is an incentive for farmers to plant more rice. Rice yields are forecasted to increase from last year but are still below average levels. The main constraints are the dry spells that occurred during the rice growing season. When looking at the regional scale, the rice cultivated area  in the north is estimated to increase when compared to the previous year. The Thai Meteorological Department forecasted that the total precipitation would be less; however, so far, the rainfall has been higher than last year. In the northeast, the rice area is expected to increase because farmers in some provinces  switched to rice instead of growing sugarcane (e.g. Surin, Burirum, Mahasarakham, Roiet, Kalasin, Khon Khan, Chaiyaphum, and Nakhon Ratchasima). Similarly as in the north, rice yield in the northeast is estimated to  increase from 2019, but will be below the 15YA due to dry spells during the growing season. In some areas of  the central region, which is the main rice cultivation region and mostly irrigated, it is possible to plant a second rice crop during the wet season. If the average rainfall conditions and high prices persist over the remainder of the rainy season, farmers will take advantage of planting a second rice crop. Good yields can be expected from the current crop and the increase in area may result in an increased rice  production in the central region as compared to the previous year.

Yields of Dry Season Rice in 2020 had decreased because water supply for the crops  was not adequate. There was a severe water shortage for these dams and reservoirs: Mae Mok (Lampang province), Ubonrat (Khon Khan province), Chulaphon (Chaiyaphum province), Lam Pra Pleng, Upper Moon dam and Lam Sang (Nakhon Ratchasima province). Government had to restrict outflow, which in turn led to drought conditions and yield reductions for dry season rice, especially in the northeast region. Due to the lack of water, poor grain quality of rice resulted and some paddies were unable to survive until the reproductive stage. Pests and diseases were an issue as well.  These are the main causes for the reduction of dry season rice yield for Thailand in 2020.

Figure 3.39 Thailand’s crop condition, April-July 2020

Figure 1.1:Phenology of major crops

Figure 1.2:    Crop condition development graph based on NDVI

Figure 1.3: Rainfall profiles

Figure 1.4:Rainfall Departure from 15YA (%)

Figure 1.5:   Spatial NDVI patterns compared to 5YA

Figure 1.6:     Maximum VCI

Sub-National Analysis

There are four agro-ecological zones (AEZ) defined within Thailand based on its cropping systems, climatic zones and topographic conditions. These are the central double and triple-cropped rice lowlands; single cropped rice north-eastern; western and southern hill; and south-eastern horticulture.

In terms of NDVI, all zones except the western and southern hill areas produced below-15-year-average NDVI until June. Afterwards, NDVI levels  recovered to average levels in July, with the north-eastern region improving to significantly above-average NDVI levels.

Table 2.1: Overall agro-climatic indicators for each sub-national regions

Table 2.2: Overall agronomic indicators for each sub-national regions

Central double and triple-cropped rice lowlands

The change in rainfall patterns from deficit to excess has been especially extreme for the central double and triple-cropped rice lowlands (figure 2.4a). The nation-wide drought  experienced since the start of the year continued in central areas for almost a month longer than in the other AEZs. When the recovery came, it was also extreme in the other direction. At the end of April, rainfall levels suddenly rebounded back to 50-100 mm per dekad. These levels were above the 15YA. Apart from a brief drop in mid-May, which occurred for all Thai regions, rainfall continued to exceed the 15YA into July. On the other hand, temperature and radiation received by central lowlands terms remained normal. The temperature closely followed its yearly pattern of gradual decrease from +30 °C down to 25 °C except for a small uptick in mid-May, when a nation-wide drop in rainfall was observed. Meanwhile, photosynthetically active radiation (PAR) fluctuated between 90 to 120 W/m2 which is at or slightly above the 15YA.

Overall, the carry-over effect of the water-shortage in the previous months impacted rice cultivation during the April-June period. This was likely reflected in the delay of the annual NDVI upturn normally associated with the beginning of the wet-season. As seen in figure 2.3a, the upturn that should have happened rapidly in May according to the 15YA had instead become a gradual rise that reached normal levels in July only. Quarterly values of CALF and VCIx also painted a similar picture of drought and recovery. For the past ten years, central areas have always had around 98% CALF regardless of season, but it dropped to 63% in the second quarter of this year (figure 2.5a). This was likely the result of the government issuing a request earlier in the year for farmers to refrain from planting second-season rice. As for VCIx, its value of 0.84 shown in table 2.2 indicates that the plants are recovering in the central areas, but not to as good conditions as in the other areas of Thailand. The Central areas can expect substantially reduced yield from second-season rice and slightly reduced yield from the main-season rice.

South-eastern horticulture area

The South-eastern horticulture area has seen its rainfall index decrease by 15% from the 15YA, temperature increased by 0.5 °C and PAR increased by 4% (table 2.1). Despite a considerable reduction in rainfall, the region received 907 mm rainfall which may still have been sufficient for the early growth of main-season rice. Thanks to the 4% increase of PAR, the BIOMASS index was estimated to have increased by 5% (table 2.1). As for the crop conditions, the low NDVI (figure 2.3b) in late May to early June was possibly due to the lower rainfall (figure 2.4b) observed during that period as compared to the 15YA. Since mid-June, the region received 80 - 100 mm rainfall every ten days which accelerated the rice development. Crop conditions recovered to average level by the end of July. Overall, the lowered rainfall in the early period of this bulletin does not appear to have significantly affected the crop conditions as reflected by a relatively high VCIx value ranging from 0.8 to over 1.0 (South-eastern horticulture area in figure 1.6). The CALF value in the area was 99% which was 1% above the 5YA (table 2.2).

Western and southern hill areas

Most indicators of the western and southern hill areas stayed close to their 15YA, with the notable exception of NDVI which dropped below its 5YA until it recovered to just about average in July (figure 2.3c). The NDVI pattern is consistent with rainfall levels which also showed a delayed start of the rainy season in mid-April followed by a recovery to above 15YA in July (figure 2.4c). Major crops of this area are Pará rubber, palm, coconut, and longan. All of these crops can be harvested all year round except longan which can only be harvested during July and August.  Since the cumulative rainfall during April-July was just about average (table 2.1), the dry condition early in the year likely didn't leave a lasting impact on these crops. This is reflected in VCIx and CALF which are measured to be 0.94 and 99% respectively during the second quarter of 2020, representing good vegetation conditions.

Single-cropped rice north-eastern region

For the north-east, dominated by  Single-rice cultivation,  rainfall (-22%) was below and PAR (+7%) above the 15YA as listed in table 2.1. More specifically, precipitation was below average throughout the period except for a few, isolated peaks in late May and early July (figure 2.4d). Meanwhile, PAR was mostly average until mid-June and then increased to distinctly above average from June onwards. In total, while rainfall dramatically declined compared with 15YA, the above average radiation benefitted biomass accumulation as potential biomass was measured to be 8% higher than 15YA (table 2.1).

For agronomic indicators, overall NDVI stayed below average except for July when the NDVI rose above the  5YA average (figure 2.3d). The significantly below average NDVI from April to June was mainly due to the rainfall shortage during that period. The rise of NDVI in July could have been a result of higher rainfall in the wet-season which helped mitigate  the drought observed earlier in the year. Moreover, VCIx across north-eastern Thailand was 0.97, which represents good vegetation conditions. The CALF value was back to 100% (table 2.2) which indicated that farmers are cultivating all of their land.

Figure 2.3a: Central double and triple-cropped rice lowlands NDVI

Figure 2.3b: South-eastern horticulture area NDVI

Figure 2.3c:  Western and southern hill areas NDVI

Figure 2.3d: Single-cropped rice north-eastern region NDVI

Figure 2.4a: Central double and triple-cropped rice lowlands Rainfall

Figure 2.4b:  South-eastern horticulture area Rainfall

Figure 2.4c:  Western and southern hill areas Rainfall

Figure 2.4d:  Single-cropped rice north-eastern region Rainfall

Figure 2.5a: Central double and triple-cropped rice lowlands CALF

Table 3.69 Thailand’s agroclimatic indicators by sub-national regions, current season’s values and departure from 15YA, April - July 2020

Table 3.70 Thailand’s agronomic indicators by sub-national regions, current season’s values and departure from 5YA, April - July 2020