Boro rice: the characteristics of Bangladesh's biggest crop

A foggy morning in January. Farmers stand knee-deep in cold water, pressing seedlings into the mud in neat rows, while beyond the ridge a shallow-tube-well pump chugs without pause. Scenes like this, repeated across the country each winter, mark the start of the boro season. Four or five months later, under the hard sun of April, the same fields turn gold, and the rice they yield feeds the country for much of the year.

Boro is one of Bangladesh's main crops, grown in the dry winter season, the rabi season. Seedbeds are sown and seedlings transplanted between November and February, and the crop is cut in April and May. It is an irrigated rice: given enough water and good care it yields well, and it plays a central part in the country's food security. What follows sets out, one by one, the characteristics that define it.

Bangladesh grows rice in three seasons: aus before the monsoon, aman during it, and boro in the dry months of winter and spring. For generations aman was the main crop, because the rain did most of the work. Over recent decades, as irrigation pumps spread and high-yielding varieties arrived, the dry-season boro crop overtook the others.

The numbers tell the tale of that change. Preliminary figures from the Bangladesh Bureau of Statistics (BBS), as reported in the press, put the boro area in the 2023-24 fiscal year at about 4.88 million hectares and boro output at about 21 million tonnes of rice. That year the country's total rice output passed 40 million tonnes for the first time, and more than half of it came from this single season.

Another estimate puts boro's share of annual rice output at nearly 55 per cent. The figure moves a little from year to year, but the picture does not: it is hard to imagine a Bangladeshi plate of rice without boro. Three changes carried it there: shallow tube wells spreading from village to village, BRRI's high-yielding varieties, and widespread use of chemical fertiliser. Together they turned much of the land that once lay fallow in winter, or carried lentils and mustard, into boro fields.

Boro's other quiet strength is predictability. The aman farmer watches the sky, waiting on rain and fearing floods. The boro farmer has his hand on the pump switch. That control is what gives farmers the confidence to spend more on seed, fertiliser and labour, and the yield rises accordingly.

Boro's first and defining characteristic is that it depends entirely on irrigation. Winter and spring bring very little rain, yet rice wants to stand in water for most of its life. From the seedbed until the grain fills, the farmer has to supply the water.

Most of it comes from underground, lifted by shallow and deep tube wells. In many areas water is also pumped from rivers, canals and beels (floodplain wetlands). The better the irrigation, the higher the yield; when water arrives late, the yield falls quickly. Diesel or electricity for pumps and the fee paid to the pump owner together make water one of the largest costs of growing boro.

That dependence has a price. Heavy pumping of groundwater is lowering water tables in parts of the country, especially in the north, and researchers now describe the decline as a national concern. Late in the dry season, shallow tube wells in many places deliver less. Saving water in boro fields is therefore not only about cost; it is about the future of the crop.

The boro season is dominated by high-yielding varieties that give 5 to 8 tonnes of paddy a hectare. That is generally more than aman or aus, because the dry season brings more sunshine and less cloud, the farmer controls the water, and the uncertainty of floods and heavy rain is lower.

The two best-known boro varieties are BRRI dhan28 and BRRI dhan29, both bred by the Bangladesh Rice Research Institute (BRRI). According to BRRI, the pair long covered more than half of the boro area between them. Research reports give BRRI dhan28 a life of about 140 days and a yield of around 6 tonnes a hectare under good management; BRRI dhan29 takes about 160 days but can yield about 7.5 tonnes. Hybrid varieties also have high yield potential, although farmers must buy fresh seed every season.

The way boro is grown has its own features too. Seedlings are first raised in a seedbed, then pulled and transplanted into puddled fields. Because seedlings grow slowly in the cold, boro seedlings stay longer in the bed; research trials describe transplanting BRRI dhan29 seedlings at about 40 days old. More telling than age is the leaf count: researchers say seedlings transplanted at the five to six-leaf stage give better yields.

Rows are usually set 20 to 25 centimetres apart, with about 15 centimetres between hills. Planting in lines lets light and air into the crop and makes weeding and pest scouting easier. Urea is normally applied not all at once but in three splits: after the seedlings have taken hold, at tillering, and before the panicle forms. The plant then receives nitrogen as it needs it, and less is wasted.

Boro's life is timed to the seasons. It starts in the cool weather of November to February and is harvested in the heat of April and May. It grows well in the cool, dry, low-rainfall months, and as temperatures rise later in the season the grain fills and ripens quickly.

Severe cold brings its own problems. During cold waves, seedlings in the seedbed can turn yellow and stop growing, which is why the Department of Agricultural Extension (DAE) and BRRI advise covering seedbeds with clear polythene during cold spells, keeping them covered day and night with the sides partly open if the cold persists, and giving light irrigation as needed. At the other end of the season, nor'westers, hailstorms and early floods can damage ripe grain, so harvesting on time is essential.

Boro farmers now grow not only high-yielding varieties but also ones that can withstand stress. In coastal districts, salt builds up in soil and water during the dry season, which harms ordinary rice. For such land BRRI has bred salt-tolerant varieties such as BRRI dhan67, approved as a salt-tolerant boro variety. BRRI data give it a life of about 145 days and a tolerance of 12 deciSiemens per metre of salinity at the seedling stage and 8 over its whole life, with yields of 3.8 to 7.4 tonnes a hectare depending on the salinity.

New varieties are also replacing the old favourites. BRRI has said that BRRI dhan28 and BRRI dhan29, after decades in the field, are losing yield potential and becoming more vulnerable to disease. Among the alternatives, BRRI dhan88, released in 2018, matures in 140 to 143 days and can yield about 7 tonnes a hectare, and BRRI dhan89 and BRRI dhan92 have out-yielded BRRI dhan29 in field trials. Some varieties can also tolerate drought or waterlogging.

Earlier salt-tolerant boro varieties paved the way, among them BRRI dhan47, selected as a salt-tolerant boro variety through participatory trials in farmers' fields. Such varieties have brought boro to part of the coastal land in districts such as Satkhira, Khulna and Bagerhat that used to lie idle in winter because of salt. A new variety takes years to reach the fields, since farmers must first get seed and then see results on their own land before they trust it; seed distribution by the DAE and the Bangladesh Agricultural Development Corporation (BADC) plays a large part in that.

Boro usually takes 140 to 150 days from sowing to harvest, about five months. It is slow because the plants grow slowly in the winter cold. Over that long period the plant builds up its reserves steadily, and that shows in the quality of the grain.

A long life has another side. The longer the land is tied up, the more irrigation it needs and the higher the cost. In the haor wetlands, late-maturing rice runs the risk of early flash floods. Choosing a variety to suit the place therefore matters: shorter-duration types where early floods threaten, longer-duration, higher-yielding types where there is time.

Boro needs a great deal of water: an estimated 3,000 to 5,000 litres for every kilogram of paddy. When supply falls short, yield falls with it; a shortage between panicle formation and flowering can leave the grain empty.

To deliver that water with less cost and waste, BRRI promotes a method called alternate wetting and drying (AWD). It was first tested in the Philippines in 2002 and first trialled in Bangladesh at BRRI in 2005. A perforated plastic pipe is set 20 centimetres deep in the field. From about 15 days after transplanting, after each irrigation the farmer waits until the water level inside the pipe has dropped 20 centimetres below the surface before irrigating again. From flowering until the grain hardens, however, 2 to 4 centimetres of standing water must be kept in the field.

According to BRRI's Rice Knowledge Bank, the method saves about 15 to 30 per cent of irrigation water, if not more, without reducing yield. Less groundwater is pumped, less diesel or electricity is used, and the farmer saves money.

The logic is that rice roots do not need to be submerged all the time. When the soil dries a little the roots go deeper and the plant grows sturdier. The pipe works as the farmer's eye: the surface may look dry, but a glance inside shows how much water is still held below. An old plastic tube or a hollow bamboo will do, so the cost is trivial.

Where farmers pay the pump owner a flat fee for the season, they have little reason to save water themselves, and researchers have identified this as one of the barriers to wider adoption. Where water is paid for by the hour or by volume, every saving goes straight into the farmer's pocket.

Some improved boro varieties resist blast disease and the leaf-folder insect. Blast is a fungal disease that leaves eye-shaped spots on the leaves; when it attacks the neck of the panicle, the whole head turns white and empty, a form known as neck blast. The leaf-folder caterpillar rolls the leaf lengthwise and eats the green tissue inside, leaving long white streaks.

Why resistance matters became clear in 2017. A study of that season identified BRRI dhan28 (29.6 per cent disease severity) and BRRI dhan29 (25.9 per cent) as the boro varieties worst hit by blast. Yet a resistant variety is no guarantee: keeping disease down still takes regular field checks, balanced fertiliser, in particular avoiding excess urea, and timely use of approved pesticides where needed.

Boro grain is generally of good quality and eats well as boiled rice. Most popular boro varieties have medium-sized, smooth grains, and much of the medium-fine rice sold in city markets comes from the boro season.

Because boro is cut in dry, sunny weather, threshing and drying are comparatively manageable. Properly dried, the paddy stores well and breaks less in the mill. A sudden April storm, though, can soak cut paddy and spoil it, so it should be threshed and dried promptly after harvest.

Judging the moment to harvest is a skill in itself. Boro is considered ready when about 80 to 85 per cent of the grains in the panicle have ripened. Cut earlier and the grain is not fully filled and breaks more in the mill; wait too long and ripe grain shatters in the field, and the risk from storms and hail grows.

At harvest time the demand for labour in the villages jumps, and in many areas workers are hard to find when they are needed. That is why combine harvesters, machines that cut, thresh and clean the crop in one pass, are spreading, especially in the haors of the Sylhet region. The government has offered a 70 per cent subsidy on such machines in haor areas and 50 per cent on the plains.

Drying the crop properly after harvest matters just as much. Wet paddy heaped in the heat spoils, discolours and loses value at market. It is best spread thinly in the sun for a few days before it goes into store or sacks. Village farmers have long tested it by biting a grain: if it cracks cleanly, the paddy is dry enough.

Boro supplies the largest share of Bangladesh's rice and is central to its food security. A good boro season keeps rice prices steady and fills government stores; a bad one pushes up imports.

How much the country leans on boro is clearest when the crop fails. In 2017 early flash floods swept through Sunamganj and the other haor districts before the rice had ripened. The DAE estimated that about 200,000 hectares of boro went under water and about 600,000 tonnes of crop were lost. A blow of that size in one season is felt in rice markets across the country. For the farmers affected it meant something harsher still: for many households that single crop was the year's food and the means of repaying loans, and one flood washed away a year of work.

The haors deserve a word of their own. Press reports put their share of national boro output at about 20 per cent. A good haor harvest brings relief to the whole country; a drowned one is felt everywhere. That is why embankment repair, shorter-duration varieties and faster harvesting machines are debated in the haors every year.

High and medium-low land, where irrigation water can be applied and drained when needed, is ideal for boro. Land that stays waterlogged all year with no way to drain is best avoided: roots cannot breathe properly there, and fertiliser and care give little return.

In the haors and beels, land lies under water through the monsoon, but once the water recedes in winter the same fields are planted with boro, often the only crop they carry all year. Success there depends on when the water goes down, the life span of the variety, and getting the harvest in before the early floods arrive.

Put together, boro's character looks like this: planted in the cold and harvested in the heat; wholly irrigated; high-yielding; long-lived; thirsty; available in disease-resistant and salt-tolerant forms; good in the grain; and the foundation of the nation's food supply. Every one of those traits is tied to a single thread, and that thread is water.

For the farmer who can give the right amount of water at the right time, choose a variety that suits the land and keep a close eye on the field, boro is the most reliable harvest there is. For the country, it is the season on which each year's rice accounts are built.

Photo: Boro rice fields in Sylhet, AbuSayeed / Wikimedia Commons (CC BY-SA 4.0)