Opening a new dimension in rice cultivation

(Left) Using drum seeder in prepared field & cultivated crop in the field

Rice production system is undergoing changes due to progressive advancement in technologies and changes in the socio-economic conditions throughout the rice growing countries in Southeast Asia. With the advent of improved agricultural machinery coupled with shortage of farm labour, mechanisation is becoming inevitable and as such we must strive to take advantage of those.

Rice cultivation in Bangladesh is predominantly practiced in transplanting method which involves raising, uprooting and transplanting of seedlings. This is rather a resource and cost intensive method since, preparation of seedbed, raising of seedling and transplanting are labour and time intensive operations. Research reports show that labour involvement in these operations consume nearly one third of the total cost of production in Bangladesh. In addition, transplanting is not a health friendly method as the farmers are to bend their heaps and stoop while transplanting rice seedlings which cause often health hazard in the older age. The countries like Japan and Korea have shifted from conventional manual transplanting to machine transplanting because there is scarcity of labour in those countries. For such machine transplanting seedlings are grown in trays under green house condition.

In China, rice crop establishment is partially done following seedling throwing method which is also a time and labour saving method. In Southeast Asian countries like the Philippines, Malaysia, Vietnam and Thailand labour shortage has resulted into a shift from transplanting to either direct dry seeding or wet seeding of rice. Direct wet-seeding of rice establishment has mitigated labour scarcity and production costs. In fact, this method can reduce labour requirement as much as 80 per cent. Direct wet seeding via hand broadcasting has been found to give 10-15 per cent increased yield. Direct seeded crops also mature 10-20 days earlier than transplanted crops. Despite these advantages, this method has also the difficulties of weed control and other cultural management resulting in little or no adoption of the practice in Bangladesh. However, much of the problems associated with direct wet-seeding by broadcasting are successfully overcome by the use of drum seeder without deteriorating yield or any other advantages of the technique.

What is a drum seeder?
Plastic drum seeder was first applied in Vietnam during the year 2000 and now about 20 per cent of the rice land, particularly in Mekong Delta is covered by direct wet-seeded rice. Drum seeder is a simple machine made of high density plastic with six to eight drums (16 cm dia) each having a pair of rows of holes (8-9 mm dia) on each side of the drum. It is used for seeding well sprouted rice seeds in rows on well prepared puddled soil directly. The machine weights only about 6 kg when empty and is very easy to transport from one place to another. When loaded with pre-germinated seeds, it weights 18-20 kg. One farmer having average health can easily pull the machine for seeding without bending his heap. This is also a farmers' health friendly device. Drum seeder is an appropriate technology to combat low profitability of rice cultivation caused by increasing production costs, lower yield per unit area and shortage of farm labour at planting time.

Introduction in Bangladesh
Drum seeder was first experimented in Bangladesh during Aman season of 2003 by the Adaptive Research Scientists of Bangladesh Rice Research Institute (BRRI), Gazipur. Several experiments conducted at research farm have very clearly demonstrated that irrespective of rice varieties, direct wet-seeded rice using drum seeder has out yielded the conventional transplanted rice by 15-20 per cent both in the Aman (July-November) and Boro (November-May) seasons. The absolute difference between direct wet-seeded and transplanted rice yields was around 1.0 t/ha. Higher grain yield in drum seeded rice is the result of many more panicles per unit areas (500-600/m2) compared to those in transplanted rice, usually 300-350/m2. Although, number of grains/panicle is reduced in direct seeded rice, this effect is more than off set by the increased number of panicles/units in direct seeded rice.

Only two persons could sow seeds on 1.0 hectare compared to about 45 persons required for uprooting and transplanting. The area of land in the transplanting method seed requirement for direct wet-seeding by drum seeder was only about 25 kg/ha (if seeded by single thin rows of the drum seeder) which is one third of that normally used by the farmers for transplanting, thus resulting in a saving of one thousand taka/ha. In addition, the drum seeded crops matured 10-20 days earlier than the transplanted rice of the same cultivars. This reduction in growth period is because this crop remains always undisturbed throughout its life cycle or never experiences any uprooting and transplanting shock. Thus, direct seeded rice has healthy and vigorous growth.

Ten to twenty days early harvest has particular significance in Bangladesh condition. In Aman season, drought occurs during the reproductive phase of rice crops (October-November) causing yield reduction. Supplemental irrigation is, therefore, necessary to realise potential yield of T. aman rice. Thus, drum seeded rice maturing 10-20 days earlier can easily escape drought. In addition, 10 days early harvest can helps the poor farmers mitigate food crisis at that time, particularly in the northern part of Bangladesh. In boro season, ripen paddy often goes under water due to flash flood in the low laying areas (during May). Ten-day early harvest can thus save the paddy crop from losses caused by climatic hazard.

Farmers also feel that use of drum seeder would reduce cost of irrigation. It has been estimated that use of drum seeder could enable rice farmers to earn an additional income of up to Tk 10,000/- per ha.

Being encouraged by the tremendous performance of drum seeded rice, efforts have been undertaken to extend the technology to the farmers' field. Results obtained from about 50 farmers' field demonstrations were very consistent with those of the research farm trials. Most of the farmers were highly impressed by the performance of drum seeded rice. However, expansion of drum seeder method is likely to be rather slow since it is a knowledge intensive technology. Some 2500 units of drum seeders were imported by the Department of Agriculture Extension in collaboration with IRRI in 2004. These machines were delivered to about 300 upazilas during the Boro 2005 season. In most cases, the results are very encouraging. The Minister and the State Minister for Agriculture and a few dignitaries have observed the impressive performance of drum seeded rice in many locations and they have emphasised for dissemination of this technology along with farmers' training. Efforts are now underway to manufacture drum seeder in Bangladesh.

How to use?
Direct wet-seeded rice using drum seeder is a knowledge intensive technology. Farmers must be trained before they apply the technology for achieving desired results.

Seed preparation and seeding: Good quality healthy seeds are to be used. Seeds are to be dried up before soaking. Seeds are to be soaked for 24 hours followed by incubation for 3-5 days depending on temperatures or seasons. Well sprouted seeds (with 4-5 mm radicles) are to be sown by the drum seeder. Before, loading in the drums, the sprouted seeds are to be lightly dried up for 1-2 hours in a shady place. Two third of the drum space be filled in by seeds and one third be left empty to ensure uniform seeding. Once the drums are filled in, approximately one acre land can be sown. Two persons can complete seeding about more than one hectare land per day. Best time for drum seeding is 01-15 July for Aman and 1-15 December for Boro.

Land preparation: The land must be well prepared to puddled condition. All weeds and stables should be decomposed. Particular attention has to be given to land leveling. This is crucial to direct wet-seeding, since sprouted seeds sown in standing water would result in seedling mortality and uneven crop establishment. Any standing water must, therefore, be drained out before sowing by drum seeder. In the boro season, the land should preferably be finally prepared one day before sowing. Seed preparation and land preparation should be synchronised. In the low laying mono crop (only boro) areas many farmers have tried drum seeder under zero tillage condition successfully. After the recession of flood water, the farmers just removed the stables from the land and leveled off the land before sowing. This enabled them saving irrigation and ploughing costs.

Water and fertilizer management: There is no need to apply irrigation up to five days after sowing. After that, water should be applied to keep the soil moist and water can be applied as the seedlings grow. However, 5-7 cm standing water is enough for the growth of rice crops. Fertilizer requirement is as usual as for transplanted rice, but Leaf Colour Chart may be used for urea management.

Weed management: Weeds could be the main agronomic constraint to direct wet-seeded rice by drum seeder, since saturated land promotes weed seeds germination and growth. Therefore, appropriate measures are to be taken to control weeds in time. Better land preparation decomposing weeds and stables is the precondition for weed free crops. However, weed infestation is very much ecology specific. In some areas, particularly the low laying single boro cropping areas, weed infestation is normally very low and only two hand weedings are adequate for keeping the rice crops weed free. BRRI developed push weeder known as "BRRI Weeder" is suitable for mechanical weed control. However, in the ecosystem where weed infestation is usually more, chemical weed control can be practiced. Farmers are now habituated in the use of herbicides in the transplanted rice. Application of herbicides (Ronstar) @ 25-30 ml mixed in 10 liters of water may be applied in 5 decimal land during 7-10 days after seeding. There must be water 2-3 mm standing at the time of applying herbicides. Inappropriate use of herbicides may result in seedling mortality. The land shall have to be kept saturated with 3-4 mm standing water for 3-5 days after application of herbicides.

Limitations and ecological niche
Besides tremendous advantages of the drum seeder technology, it has also some limitations. Water management is crucial for direct wet-seeding. During boro season, about 30 days early irrigation facility is to be ensured. The farmers who have their own shallow tube-wells are in favourable position. Farmers under deep tube well command areas must be organised to install irrigation infrastructures in time. Availability of electricity is also important for this purpose. Thus, community approach would be highly effective for dissemination of the technology. Drum seeder is most suitable for Boro season since water management is in control of the farmers. Particularly, in the low laying areas of Gazipur, Tangail, Sirajganj, Pabna, Natore, Mymensingh etc. where just after the recession of rainy season water in the month of November, farmers can start seeding with minimum tillage. The technology is also adaptable for Aman season on the high and medium highland areas where there remains no standing water at the time of seeding, and heavy rainfall would not disrupt the sprouted seeds sown in lines.

In the northern districts, where low temperatures in the month of December may cause seedling mortality, seeding should be completed by early December. Mid November to mid December sowing would result in optimum yield. Farmers have also started the use of drum seeder for Aus season. They have successfully established Aus rice in many viz. in Faridpur, Barisal, Jessore, Gazipur, Mymensingh, Moulvibazar etc. Among the biological constraints weed infestation has been observed as the most serious one. Use of pure seeds would help controlling weedy rice in the drum seeded rice land.

Conclusion
Direct wet-seeding of rice using drum seeder may bring a revolutionary change in rice cultivation in Bangladesh. Farmers may earn additional Tk one thousand per bigha (33 decimal land) through adoption of this technology. Policy makers may extend support to facilitate rapid dissemination of the technology.

Dr. Musherraf Husain is Chief Scientific Officer, ARD, Bangladesh Rice Research Institute, Gazipur.