by: Dr. Sosimo Ma. Pablico

Researchers at the Philippine Rice Research Institute (PhilRice) have developed a modified method of producing hybrid rice seedlings that cuts on the amount of seeds used and the production cost.

The new method is called modified dapog method, as it follows the principles of the original dapog method. The great difference is that instead of sowing the seeds on banana leaves placed on top of the seedbed, the seeds are sown on top of a double layer of plastic mosquito net, which is used as a lining above the seedbed.

The seeds are spread evenly on the upper layer of plastic net and, hence, the roots of the seedlings would not penetrate deep into the soil.

Thus, instead of pulling the seedlings, all that the farmer needs to do is roll the seedlings together with the upper layer of mosquito net. The lower layer is left on top of the seedbed to remove the carbonated rice hull attached to the roots.

The modified dapog method was developed by Dr. Rodolfo Escabarte Jr., Dr. John C. de Leon, Mrs. Evelyn C. Javier and Mr. Nori Jose Buhat. Escabarte is the branch manager of PhilRice Midsayap, while Dr. de Leon and Javier are from the PhilRice Central Experiment Station in the Science City of Munoz. Buhat is also with Midsayap.

The new method requires that the seedlings are transplanted at 10 to 12 days old. This differs greatly from the conventional wetbed method wherein 21-day old seedlings are transplanted. However, extra care and proper management are needed in applying the technology.

The new method needs only P8,000 for a hectare, while the conventional method spends more than P9,000 a hectare. This amount includes the cost of land and seedbed preparation, transplanting and replanting under Midsayap condition.

Escabarte said that with the modified dapog method, 12 to 15 kg of Mestizo hybrid seeds would be enough for a hectare as long as one to two seedlings are transplanted per hill. In contrast, the wetbed method requires 17 to 20 kg Mestizo hybrid seeds for a hectare.

What’s more, the modified dapog method cuts down on labor cost because smaller seedbed and minimum maintenance are needed. The seedlings are simply rolled from the seedbed before transplanting, thereby eliminating pulling cost and facilitating transport and distribution during transplanting.

Moreover, the short period of raising the seedlings promotes better recovery and growth because of less root damage.

Dr. Escabarte emphasized, however, that the new method must be practiced only in irrigated areas with good drainage and which are not prone to golden apple snail attack.

The rice field must be leveled well before transplanting to avoid golden apple snail infestation, as the snail attacks the new transplants in depressed portions of the field.

Step by Step Procedure

The modified dapog method is easy to follow. Dr. Escabarte said here’s how to do it:

Seeds. For a hectare field, prepare 12 to 15 kg certified seeds of PSB Rc72H (Mestizo 1) or NSIC116H (Mestizo 3) with a germination of at least 90 percent.

Land preparation. Prepare the land thoroughly with one plowing, two rotavation and final leveling. The area must be properly levelled as this is critical on water and golden kuhol management for dapog seedlings.

Seedbed area. Set aside an area of about 25 m long x 1 m wide as seedbed site.

Materials. Prepare the following materials:

— 5 to 6 bags of fresh unburned rice hull (25 to 30 kg) as seedbed flooring. Better still, use carbonized rice hull [CRH].

— 5 to 6 bags clean, dried rice straw as seedbed cover

— 26 sheets plastic mosquito net, each measuring 2 m long x 0.75 m wide

Seed preparation, seedbed construction and seed sowing

— Place the seeds in a sack with enough loose space inside. Soak in clean or running water for 12 to18 hours until the seeds swell. Wash the seeds every six hours when soaked in stagnant water.

— Incubate for 24 hours. Periodically turn the seeds upside down and sprinkle water until white dot or protrusion of the first roots is observed.

— While soaking the seeds, prepare the seedbed, 0.75 m wide and 25 m long per plot. Elevate the plots to about 6 cm (2 inches) high. The canal between plots must be about 50 cm wide.

— Scatter either fresh rice hull or CRH evenly on the seedbed to about 3 cm (or 1 inch) thick.

— Place a double layer of plastic mosquito net on top of the rice hull, properly leveling its surface with the seedbed.

— Sow the seeds evenly on top of the plastic net with seeding rate of one (1) kg per sq m. This means that you need about 1 kg seeds for a seedbed that is 2 m long and 0.75 m wide.

— Cover the seeds with rice straw (about 2 to 3 cm thick) just enough to prevent direct exposure to sunlight but with good aeration. If rainfall occurs after covering with rice straw, facilitate good drainage and make sure there is just enough moisture in the straw to prevent rotting or drying of geminating seeds).

— Flood the plot up to the level of the plastic net and manually sprinkle water on the rice straw until it is wet. Drain the plot immediately. Do this until 4 days after sowing (DAS).

Seedling maintenance

— In the afternoon (or morning when sowing was done in the afternoon), introduce irrigation water inside the plot canal only, and then sprinkle water to rice straw cover until wet condition. Do this also until 4 DAS.

— In the morning at 5 DAS, remove the rice straw cover and introduce water to about 1 to 2 cm deep from the plot surface.

— In the afternoon (about 3:00 pm), apply 1 kg ammonium sulfate for every 10 kg of seeds. Immediately sprinkle little water to prevent leaf or seedling burning. Fertilizer application in the afternoon could also prevent seedling burning.

—Maintain 2 to 3 cm deep water inside the plot until 9 DAS in the morning. Drain the plot in the late afternoon so the seedlings would not be flooded in case it rains . Pesticides could be applied if necessary.

Seedling harvest. At 10 DAS, individually separate the double layer of plastic net to remove some rice hull and soils attached to the roots. This facilitates easy pulling of seedlings from the plastic net and detaching them individually. The upper plastic sheet can hold the seedlings and can be rolled to facilitate seedling distribution in the field.

Transplanting. Transplant one seedling per hill in a 20 x 20 cm spacing. [With reports from Charisma Love Gado and Sahlee Abdullah]