Traditional Aus rice is a kind of rice grown from March to August under rain-fed conditions where water is not controlled by levee around the land.

The topography varies mainly from highland to medium highland.  The crop is established through the direct seeded method in a well-prepared land under field capacity of the specific soil. According to Khona Devi (a scientist born in Bengal some two thousand years back), “sandy soil is appropriate for Aus”.  It means that the Aus rice does well not grow where the soil is not properly drained. We consider sandy loam is better for growing Aus rice. The Aus crop has to encounter a lot of adverse conditions. The season starts with scorching sun with sporadic drought at the beginning. Some years the field goes so dry having no rain for few months prior to sowing. Then the farmers have to go for dry seeding and to wait for rain. This is called Khorani in Bangla, also a traditional practice of crop establishment. By nature, the Aus rice is tolerant to drought at the vegetative stage and to high temperature at the reproductive stage. Khona has a saying on Aus rice something like as:  
Drought in May followed by a heavy rain,
Dry stalks grow green to yield better grain.

Generally drying up of the growing shoots of the plant at its early vegetative stage due to the severe drought helps to break the apical dominance to regenerate new tillers profusely immediate after the monsoon rain. This is a special attribute that exists only in the traditional Aus varieties, not in the others. Sometimes the farmers impose some artificial treatments like laddering to bruise the base of the plant at the early vegetative stage of the crop to enhance profuse tiller growth. A lot of tiller means a lot of leaf area for the economic use of solar energy to convert into higher yield.

BRRI executed a study on the performance tillering ability of some traditional Aus varieties (Pukhi, Surja mukhi, Kala manik, Sukhti, Jhuma). After the treatment (laddering) imposed to break the apical dominance, the traditional varieties had far better regeneration ability compared to those of the BRRI developed rainfed upland (Aus) rice varieties like BRRI dhan43 and BRRI dhan65. It means BRRI has yet to work more to develop a real Aus variety.

Though Aus rice prefers to grow better under upland conditions, the reproductive and maturity stage of the crop has to encounter the rainy season. Even in the lower topography or in the charland farmers have to harvest their Aus crop in a knee to waist deep water. There is a perfect example of the rainy season and harvesting of Aus rice in the Rabindranath:

Clouds rumbling in the sky; teeming rain.
I sit on the river bank, sad and alone.
The sheaves lie gathered, harvest has ended.
The river is swollen and fierce in its flow.
As we cut the paddy it started to rain.

The traditional Aus rice is quite eco-friendly. But our predecessors did not have any options other than growing HYV to feed the teeming millions. So the most of the Aus and deepwater rice (DWR) land was transformed to irrigated rice preferably called as Boro rice as they are grown in the Boro season (November to May). In 1970, the boro cultivation was mostly confined to the haor and some low-lying area of the country. The coverage of Boro that time was only 0.32 million hectare. In contrast, the coverage under traditional Aus and DWR was around 3.0 and 1.77 million hectare. The present scenario is just opposite. The coverage under Boro is 4.87 million hectares just grabbing land from the Aus and DWR.

Now the traditional Aus is no more able to stand on its original foothold. Because the yield of traditional Aus is quite low and the plant architecture is not up to the mark. So farmers need HYV Aus. To satisfy the demand BRRI developed some varieties not bad for upland culture. But still, yield is a matter of concern.  So they have to develop rain-fed lowland Aus varieties also. Accordingly, BRRI had a variety rain-fed lowland variety BRRI dhan48, one of the highest yielders in Aus season released a few years back. BRRI dhan65 is the latest upland HYV released in 2014 with a growth duration of fewer than 100 days.  But I am sure those Aus varieties are not like traditional varieties as they do not have regeneration ability after the drought as described earlier. Even they are not tolerant to high temperature in their critical stages.

In the recent past, BRRI scientists were in concern on the issue of decreased Aus rice coverage. They were in a mental exercise how to go back to the water-saving Aus cultivation.  Maybe not all Boro land is possible to get back, and that should not be but a portion is not bad. They executed some estimation on the issue. Let’s consider some 20% of the rice neat land equivalent to 0.829 million hectares is get back from Boro coverage. Then the present coverage under Aus rice would be 1.85 million hectares to affect the Boro rice production by 3.18 million tonnes of rice (clean rice: Chaul). Right now the per hectare yield of lowland HYV Aus is little more than 2.02 tonnes per hectare. Thus the total production of Aus will increase 5.25 million tonnes per hectare. So there will be no shortage of rice provided the yield of Aus is maintained.

Here Aus stands for lowland HYV Aus. It’s a simple arithmetic calculation. There is a simulation study also. In this study, the transformation of land from Boro to (lowland) Aus has been considered 15 per cent. Following this trend, the Aus land will be 2 million hectares by 2030. The projected yield of Aus rice is expected to 2.72 and 3.20 tonnes per hectare by 2020 and 2030, respectively. Considering the climate and market impact the total rice production would be 47 million metric tonnes by 2030. The population will be 190 million by 2030. To satisfy these people 28 million tonnes of rice will be needed.

The food habit change was considered in this calculation. Thus, 19 million tonnes of rice will be excess. This estimation might vary on the methodology and the objectives. The objective of this estimation was how to shift Boro by Aus gradually.  The weakness of these estimations was the consideration of Aus as rainfed lowland rice where yield is higher. In the case of upland culture, the estimation must be revised. The introduction of Aus is quite challenging whether we go for either upland or lowland culture. In both cases, we need a variety must have better regeneration ability after the stress, tolerance to drought and high temperature. Some forty years back the coverage under the Aus culture was in upland conditions. With times those lands have already been transformed to lowland culture. So it would be another challenge if we want to get them ready again for upland culture. The most of the upland soils have lost their identity e.g. they have now less macropore with shallow plough pan having poor drainage abilities. Therefore prior to going for Aus extension we have to decide how much we can go for upland Aus culture and how much for the lowland Aus. Or another option is to develop the aerobic rice verities facultative in nature with the mechanism of adaptation in either of the situations.

What is BRRI doing in align with the development of Aus rice varieties? The temperature is in the increasing trend. The temperature injury of Aus rice is getting importance in the recent years. So the incorporation of high-temperature tolerance attributes in the modern Aus varieties is earnestly felt by the scientists. So BRRI scientists are screening for high-temperature traits in the germplasm materials. Interestingly they have discovered the traits in the DWR varieties like Hasfal Boron, MollahDigha, and Abchaya. Besides these, they have exploited the traits from extensively discussed traditional Aus genotypes Kasalath from Sylhet area. Kasalath is a phosphorus efficient variety also. The other traditional varieties like Dular are also high temperature tolerant. BRRI scientists have transferred the major effect spikelet fertility QTL qSF4.1 and minor effect fertility spikelet QTL qSF4 from an Indian high-temperature tolerant N22 to BRR28 and BRRI dhan29 through marker assisted selection technology. The growth duration of N22 is 90 days. So there are some breeding lines whose growth duration is within 90 days too. This work is in progress under the care of BRRI Plant Physiology Division. They are expecting verities tolerant to high temperature within a few years. Similarly the screening out of the photosynthetically efficient germplasms under low light intensity in under way. However, with the incorporation of high-temperature QTL the introduction other attributes for traditional Aus rice must not be overlooked. And it is better the variety should be facultative in nature so that they could be grown in the upland or lowland conditions depending on the situations.

Now a remark. Is it possible to grow a traditional Aus rice as Boro? Most of the photoperiod insensitive HYV variety good for growing all over the year provided the most sensitive reproductive stage must not coincide with the extreme low and high temperature. Accordingly many of the rice varieties were recommended both for Boro as well as for Aus. In fact, they are good for Boro not for Aus. Farmers’ are using the spill over benefit of those varieties in Aus season. Conversely, a real or traditional Aus varieties cannot be grown in Boro. An Aus rice varieties must have some specific traits I have mentioned. In addition, they should have the ability to elongate their coleoptile from the deep dry seeded conditions for better crop establishment even under water stress conditions.  The traditional upland varieties have more or less all of these traits. But they are not tolerant to cold. Though the upland rice (Aus) varieties have originated from their aquatic ancestors, but they do not grow well in the lowland culture. Even their growth duration cannot be guaranteed within 100 days for safe harvest prior to the early flash flood. Therefore, a variety exclusively developed for Aus season or a traditional Aus variety cannot be recommended for Boro seasons as the two varieties belong to the two distinct ecotypes.

However, Aus rice is a good source of many desirable traits like phosphorus-starvation tolerance 1 genes (PSTL1 from Kasalath), Submergence gene (Sub 1 from FR13) etc. So the probability to exploit a short duration gene is not unlikely from an Aus rice group. I have explained the fact to some extent in my write up in the daily sun published on 25 March 2017 (http://www.daily-sun.com/printversion/details/214605/ Banabhatta%E2%80%99s-Sixtyday- RiceVariety:-Can-We-Get-It-Back).

The writer is the Director General (PRL), Bangladesh Rice Research Institute,Gazipur