Drum Seeder for Aman Rice: Sowing Sprouted Seed When Rain Ruins the Seedbed

Every rainy season some Bangladeshi farmers watch the same thing happen: days of steady rain, water standing in the fields, and the aman seedbed they had raised for transplanting rotting under it. In late August 2024, sudden floods driven by heavy rain and a monsoon depression in the Bay of Bengal hit at least 12 districts, and the Department of Agricultural Extension (DAE) said 19,680 hectares of aman seedbeds had been completely devastated, The Business Standard reported on 27 August 2024.

One answer the Bangladesh Rice Research Institute (BRRI) has offered since 2003 is the drum seeder, a light plastic machine that sows sprouted rice seed in straight lines on puddled mud, so the crop needs no seedbed, no uprooting and no transplanting. This report explains what the machine is, what BRRI and the International Rice Research Institute (IRRI) found in aman trials, which rainy-season land it suits, how to sow and weed, and BRRI's other options when a seedbed is lost.

Aman is Bangladesh's main rainy-season rice. Banglapedia, the national encyclopedia, records that transplanted aman was the most important of the country's rice crops, occupying about 46 percent of the rice land in 2009-10, and that it is grown throughout Bangladesh; sown or broadcast aman is grown mostly in the south and south-east. Transplanted aman is harvested from November to January.

Because the crop is raised in the monsoon, its weakest point is the start. A BRRI fact sheet on disaster management in rice notes that in flood-prone areas the aman crop is usually damaged at its early stage, in the seedbed or while tillers are forming after transplanting. Farmers then have to raise and transplant seedlings again, so their costs rise, transplanting is delayed and yields fall well below normal.

The 2024 season showed the scale of the problem. According to Ministry of Agriculture data cited by The Business Standard on 27 August 2024, the floods affected 2,91,033 hectares of land under aman and aus rice, and rice production could fall by 8.5 lakh tonnes. On 7 September 2024 The Financial Express, citing the ministry, put the damage to agriculture in 23 eastern districts at Tk 33.46 billion, including 14,908 hectares of ropa (transplanted) aman seedbeds, with more than 1.4 million farmers affected.

The damage was not confined to the east. The DAE told the Dhaka Tribune, in a report of 7 September 2024, that rain and flooding between 22 and 26 August destroyed 136 hectares of aman seedbeds belonging to 2,845 farmers in Khulna, Bagerhat, Satkhira and Narail, a loss of Tk 68.60 lakh.

BRRI describes the drum seeder as a modern sowing machine made of plastic that sows sprouted seed directly into muddy, puddled soil in rows. In a 2005 article in The Daily Star, Dr Musherraf Husain, then chief scientific officer at BRRI, described it as a simple machine of high-density plastic with six to eight drums, each about 16 cm across, with a pair of rows of holes of 8-9 mm on each side of every drum.

The drums sit on a central axle between two large plastic wheels and are pulled by a handle. As one person pulls the machine across the field at walking pace, the sprouted seeds drop through the holes in neat lines, IRRI's Rice Today magazine explained in September 2005. With six drums, BRRI says, the machine sows 12 lines at a time.

It is light. Dr Husain wrote that the seeder weighs only about 6 kg empty and 18-20 kg when loaded with pre-germinated seed, so a farmer of average health can pull it without bending.

The machine was originally designed by IRRI, and researchers and manufacturers in Vietnam later made it lighter, cheaper and easier to use, Rice Today reported. In 2005 it cost around US$40 and lasted six to eight years. Plastic drum seeders were first used in Vietnam in 2000, according to Dr Husain. IRRI's Rice Knowledge Bank adds that a drum seeder works best on a well-levelled, smooth and wet seedbed, and that it can clog if the soil is sticky or the machine is poorly designed.

BRRI introduced the drum seeder to Bangladesh in 2003, and the first trial was in the aman season. According to Rice Today, it was a collaboration between IRRI and BRRI funded by the International Fund for Agricultural Development (IFAD), led by M. Zainul Abedin of IRRI and carried out by BRRI's Musherraf Husain with participating farmers.

In the trial, drum seeding gave on average 18 percent higher yields and 6 percent lower costs than transplanting, the crop matured on average 10 days earlier, and gross returns were 21 percent higher. Rice Today said this meant more than double the average profit, a gain of around US$120-150 per hectare per crop. Farmers in the trial saw the machine as cheaper and less labour-hungry; their concerns were the cost of buying one, whether it would be available, and weeds.

Wider use followed quickly. Dr Husain wrote that the DAE, together with IRRI, imported some 2,500 drum seeders in 2004 and delivered them to about 300 upazilas for the boro season of 2005, with results that were in most cases very encouraging, and that efforts were under way to make the machine in Bangladesh. BRRI's fact sheet states that the drum seeder is now made in Bangladesh.

The reason for the interest was labour. Rice Today noted in 2005 that almost 90 percent of the 11 million hectares planted to rice each season in Bangladesh was transplanted, which took nearly half a billion person-days across the country, while workers were leaving for the cities and other jobs. Transplanting one hectare could take up to 50 person-days; drum seeding took barely two.

BRRI's research farm compared drum-seeded and transplanted crops of the same varieties. In its fact sheet, BRRI dhan30 yielded 5.35 tonnes per hectare when drum-seeded against 3.76 tonnes transplanted, a 42 percent gain, and its life cycle fell from 148 to 132 days. BRRI dhan31 gave 3.70 against 3.25 tonnes, 13 percent more, and finished in 118 days instead of 137. BRRI dhan41 gave 5.50 against 4.40 tonnes, 25 percent more, in 129 days instead of 139.

In farmers' fields in the aman season of 2004 and the boro seasons of 2004 and 2005, BRRI found yields about 15 to 20 percent higher than transplanting and a harvest 10 to 12 days earlier. It estimated that a farmer could earn about Tk 6,000 more profit per hectare in aman and about Tk 8,000 more in boro by drum seeding instead of transplanting. Those are BRRI's figures from its trials of that time, not a promise for every field.

Inputs fell too. Two people could sow a hectare that needed about 45 people for uprooting and transplanting, he wrote. Seed needed was only about 25 kg per hectare when sown in single thin rows, about one third of what farmers normally used for transplanting, a saving of about one thousand taka per hectare.

The earlier harvest matters most in aman. Dr Husain noted that drought occurs during the aman crop's reproductive stage in October and November and cuts yields, so a crop that matures 10 to 20 days earlier can escape it. He estimated that drum seeding could add up to Tk 10,000 per hectare to a farmer's income.

Drum seeding is not right for every aman field. Dr Husain wrote that it is most suitable in boro, when farmers control the water. In aman, he said, it is adaptable on high and medium-high land where no water stands at the time of seeding and heavy rain would not disturb the sprouted seeds sown in lines. He gave 1 to 15 July as the best time for drum seeding in aman and 1 to 15 December in boro.

BRRI's fact sheet on sowing lists the risks a farmer must weigh in the rainy season:

• Heavy rain within 24 hours of sowing can scatter the seed out of its lines.
• If the land is uneven or water collects in the field, the sprouts can rot.
• Where many weeds grow, a herbicide becomes necessary.
• Birds, ducks and chickens can do damage in the first seven days after sowing.
• In aman, sow on the same day the land is prepared; in boro, sow the day after.
• In aman, sow on medium-high land and avoid sowing during rain.

Dr Husain of BRRI called direct wet seeding with a drum seeder a knowledge-intensive technology and said farmers must be trained before using it. Its fact sheets and Dr Husain's 2005 guidance set out these steps:

• Prepare the land well: plough and ladder the field so that weeds and other trash are rotted into the soil, and bring it to a puddled state.
• Level the field with great care. Sprouted seed sown into standing water dies or comes up unevenly, so drain any standing water before sowing.
• Use good, healthy seed. Soak it in water for 24 hours, then keep it warm for sprouting (incubation) for three to five days depending on the temperature and season.
• Sow well-sprouted seed with roots (radicles) about 4-5 mm long.
• Before loading, dry the sprouted seed lightly in the shade, for about one to two hours, so that it falls freely and evenly through the holes.
• Fill each drum to two-thirds with sprouted seed and leave one-third empty so the seed flows evenly. With six drums the machine sows 12 lines at once; one filling sows roughly an acre.
• Pull the machine steadily across the field. Two people can sow more than a hectare in a day.

Water is handled differently from a transplanted field. BRRI says no standing water is needed in the early stage after sowing; the soil should be kept moist, and irrigation increased as the seedlings grow. Dr Husain wrote that no irrigation is needed for up to five days after sowing, and that 5-7 cm of standing water is enough for the growing crop.

Fertiliser is the same as for transplanted rice at the recommended rates, BRRI says, and a leaf colour chart (LCC) can be used to decide when urea is needed. Farmers should get the recommended fertiliser rates for their soil and variety from the upazila agriculture office.

Weeds are the biggest weakness of the method. BRRI's weed fact sheet explains why: after drum seeding, the muddy field is not flooded for some days, and saturated soil without standing water lets weeds germinate and grow. Weed pressure also varies from place to place and field to field; BRRI says low-lying, single-crop land usually has fewer weeds.

BRRI divides control into indirect and direct methods. The indirect ones are prevention:

• Use good seed free of other varieties and weed seed; seed mixed with weed seed is one of the main ways weeds get in.
• Choose land where weeds are usually few, and prepare it well, with timely ploughing and laddering that rot the weeds into the soil.
• Sow properly so the stand is dense; a dense crop leaves less room for weeds.
• Manage water so that standing water is kept once the seedlings are big enough.

The direct methods are hand weeding, a mechanical weeder and herbicide. Hand weeding works best but is slow and costly; BRRI says two or three weedings are enough. The BRRI Weeder, a push weeder developed in 1985 by BRRI's farm machinery and postharvest technology division, has been matched to the drum seeder; it is 12 cm wide. BRRI's fact sheet says it weeds about 50 decimals a day, takes a quarter of the time of hand weeding, and can be made and repaired in local workshops. It can be used in aus, aman and boro, but only in line-sown or line-transplanted fields, and it needs water in the field. The fact sheet listed its price at Tk 500.

For herbicide, BRRI's fact sheet gives 20-25 ml of Ronstar or 10-12 ml of Rifit mixed in 10 litres of water for every 5 decimals of land. In the aus and aman seasons, it says, herbicide is best applied within four to five days of sowing. In boro it is applied within 7-10 days with a thin layer of standing water in the field, which is then kept for another four to five days. BRRI warns that herbicides must be used carefully and that timing, dose and water management are critical, because misuse can kill seedlings. Farmers should check the product and dose with the upazila agriculture officer before spraying.

BRRI's fact sheet reports that farmers in the Board Bazar area of Gazipur controlled weeds in drum-seeded rice with only two hand weedings. Its advice is to use the drum seeder where weeds are few.

The drum seeder is one tool among several that BRRI recommends when floods upset the aman calendar. Its fact sheet on technologies for flood-affected areas sets out these choices:

• Where fields may be submerged for 12 to 16 days during transplanted aman, BRRI dhan51 and BRRI dhan52 can give satisfactory yields.
• After a flood recedes, sprouted seed of BR1, BR11, BR22, BR23, Nizershail and similar varieties can be sown directly on muddy, level land; sowing should be finished by early September (mid-Bhadra).
• For replanting after a flood, choose photoperiod-sensitive varieties such as BR22, BR23, BRRI dhan37 and BRRI dhan38. Seedlings of BR22, BR23 and BRRI dhan46 aged 30 to 50 days can be transplanted up to mid-September (the end of Bhadra) and still yield well. For late aman, seedlings 45 to 50 days old do best.
• Where flooded BR11, BRRI dhan32, BRRI dhan38 or BRRI dhan39 has not died completely, a light top dressing of urea when new tillers begin after the water drains can help the crop recover.
• If flooding delays aman planting too long (into the first half of September), BRRI advises thinking about an early boro crop instead, with seedlings raised in mid-November.

When no high land is left for a seedbed, or there is not enough time after the water recedes, BRRI describes a floating seedbed. A raft of bamboo mats or banana stems is built on flood water, a pond, a ditch or a canal, covered with a 2-3 cm layer of mud, and sown with sprouted seed like an ordinary wet seedbed. The raft is tied to stakes so it does not drift away, and because it floats it needs no irrigation.

Farmers who want to try drum seeding, or need advice after a flood, can contact the upazila agriculture office of the DAE. BRRI's fact sheets direct further questions to the Director (Research), BRRI, Gazipur-1701.

Photo: SEJustice / Wikimedia Commons (CC BY-SA 3.0)

Sources: The Agro News (Staff Correspondent), Bangladesh Rice Research Institute (BRRI) Rice Knowledge Bank and fact sheets, International Rice Research Institute (Rice Today, Rice Knowledge Bank), The Daily Star, The Business Standard, The Financial Express, Dhaka Tribune, Banglapedia