Re-thinking Upland (Aus) Rice Systems

In Bangladesh, Boro rice is directly related to food security. Boro is a fully irrigation-dependent crop. In contrast, the other two rice seasons, Aman and Aus, are rainfed. However, farmers provide irrigation if the crops encounter severe drought. The area coverage under Aman has remained at about five million hectares over the ages. But the coverage of Aus has severely shrunk (from three million hectares in the 1970s to 0.5 million hectares in recent times) due to its low yield, as no real high-yielding Aus variety is still available. In contrast, the coverage under Boro has increased from 0.50 million hectares in 1970 to around five million hectares in recent times, of course, with the extension of irrigation facilities grabbing land from the Aus area.
Therefore, farmers have to withdraw a huge amount of underground water each year to satisfy the demand of Boro rice through shallow or deep tubewells, causing a sharp decline in the groundwater table, even below the threshold level during the peak period in many areas of the country. Thus, the country has to encounter severe consequences, such as environmental, economic and social challenges. Meanwhile, the cost of inputs and labour is on an increasing trend.
Continuous submergence due to intensified irrigation increases pest pressure and degrades soil physico-chemical conditions, while it also acts as a major source of GHGs, particularly methane, which is considered a potential global warming threat. Given these pressures, reconversion of Boro-growing areas to Aus (upland) growing areas appears to be a viable option.
In rice science, upland rice does not imply that rice is cultivated only at higher toposequences. Rather, it refers to a type of rice that is grown under rainfed conditions in aerobic soil environments, regardless of whether the elevation is high, medium or low. In Bangladesh, upland rice – traditionally called Aus – is directly sown in April and harvested by July. Early-season rainfall associated with nor’westers helps establish this rice and other upland crops such as minor cereals, jute, sesame, etc. This system is particularly well suited to the drought-prone western and northwestern regions of the country. Even along river basins such as the Padma, Jamuna and Old Brahmaputra, it is suitable for upland crops.
Generally, upland rainfed rice and other upland crops do not need irrigation. However, supplemental irrigation at any stage of the growing period may be required due to the erratic behaviour of rainfall patterns. Even then, the amount of water required is significantly lower than that needed for irrigated rice cultivation.
According to an ancient proverb attributed to Khona, a legendary wise woman who was skilled in astronomy, agriculture, and mathematics, and whose wise sayings (Khonar Bachan) are still popular today, ÔÔ‰R¨‰ô Liv, av‡bi fivÓ (A rice that withstands May-June’s drought yields abundantly). Despite long-standing recognition of this need, suitable high-yielding upland rice varieties for Aus conditions with regeneration ability after drought shock remain unavailable, and existing varieties have failed to achieve widespread adoption due to their limited performance. Although BRRI has released some varieties such as BRRI dhan24, BRRI dhan42, BRRI dhan43, BRRI dhan65, and BRRI dhan83, designated as upland rice varieties, their tolerance to drought and regeneration ability after drought shock, as described by the great Khona long ago, are not comparable to those of traditional Aus rice varieties.
In contrast, there are some high-yielding varieties such as BR26, BRRI dhan48, BRRI dhan82, BRRI dhan98, and BRRI hybrid dhan7 that have been released as transplanted Aus for rainfed conditions. Therefore, they are designated as transplanted Aus.
Therefore, target-orientated research is essential to develop true upland or Aus rice varieties with rapid establishment, drought resilience with regeneration after shock, weed suppression capacity and responsiveness to standard agronomic management. Complementary technologies – such as conservation tillage, laser land levelling, precision seeders and water-saving irrigation methods (e.g. sprinkler systems for extreme drought) – should be developed in parallel. While the development of an ideal variety may take a decade or more, available varieties must be utilised with appropriate agronomic management.
In addition to varietal and agronomic management development, training for farmers’ capacity enhancement is crucial. The responsible research institute, BRRI, and the extension agency, DAE, are the relevant organisations to execute these programmes under the guidance of the Bangladesh Agricultural Council. The Ministry of Agriculture should seek assistance from international partners such as FAO, IFAD and IRRI, which work on developing mitigation technologies for GHG emissions. The Ministry should establish a comprehensive framework for specific upland rice system development immediately.
However, it would not be wise to attempt replacing irrigated Boro rice with the upland or Aus rice varieties mentioned above within a few years. Instead, a well-planned gradual recovery process is needed, with real upland rice varieties to be developed in the near future. Then, the existing Aus area could be cultivated with true high-yielding upland/Aus rice varieties. Vis-à-vis, a significant portion of the Boro area could be brought back to Rabi as well as upland rice crops during the Boro season. Even Rabi crops could be followed by upland Aus rice. Upland Boro would be a new and innovative approach in the arena of climate-resilient agriculture. This process may take several years to several decades. Therefore, there should be short-, medium- and long-term plans with a target-orientated vision and mission. I am confident that farmers will adopt this eco-friendly approach to achieve national, sustainable, climate-resilient food security.
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The writer is former Director General of BRRI and former Executive Director of KGF