IRRI agronomy challenge: choosing the right variety

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January 6: We need to prepare seed. Which variety should we grow? After some debate we’ve settled on NSIC Rc222, which is a modern rice variety released in the Philippines in 2010. It’s also known here as Tubigan 18, but it’s actually a variety bred by IRRI, named by us as IRRI154.

Achim Dobermann and Leigh Vial discuss what variety of rice to use in their experimental rice crop.

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This is how it works in breeding. New varieties or hybrids are nowadays mostly released through the national variety release systems, and in countries such as the Philippines they therefore also receive names assigned by that country.

Why did we choose it? First of all, we think it is important to grow a recently released variety that is well-adapted to our location because it will have a better chance for a higher yield. In our research we have found that varieties that were released 20 or 30 years ago often yield about 1 ton/hectare less when they are grown today as compared to the time when they first appeared. They are just not adapted anymore to the changing environment. Since the 1970s and 80s, climate has changed somewhat, but pathogens causing rice diseases or insects attacking the crop have also evolved to overcome resistance built into modern rice varieties. Management practices also change. Hence, it is important to replace varieties regularly. That alone can make a 5-10% yield difference.

Secondly, we chose this variety because it has performed well in national trials, yielding 6-8 tons/ha under direct-seeded conditions with standard management. It should mature in about 105-110 days (around April 20), which is also desirable for us because we want to avoid that flowering and grain filling take place during the extremely hot period of the year. Finally, it meets the desired grain quality characteristics needed for the local market, and it has well-rounded resistance to all major diseases and insect pests. Hence, we hope that we don’t have to spray much pesticides.

The second decision we made is to use certified seed, which should have greater vigor for good emergence, and it is also likely to contain no contaminations with diseases or weed seeds, which is often a problem when farmers keep their own seed. We think that using certified seed can set the basis for another 5-10% yield advantage.

Seed from the rice variety Tubigan 18

Seed from the rice variety Tubigan 18.

Preparing the seed was really easy. We figured that we should have at least 20 kg seed at hand, which would allow us to sow at a rate of up to 80 kg/ha. We soaked this seed in water for about 24 hours, and then let it dry off in a bag. This worked really well. Ok, there is really not much to screw up with that, we admit it. Anyway, seed prepared this way is pre-germinated, with just 2-3 mm of root popping out, which is good for getting fast and uniform emergence in the field.

Lessons learned

Although the rationale provided above seems logical, it wasn’t that easy to pick this variety. We found a lot of information in various materials available on the internet, but it wasn’t “actionable”. What we would have wanted is a simple, more concrete variety selection tool that could have guided us to a few specific options, and also provided us with enough variety performance information for making the final choice. The latter doesn’t seem to be easily accessible. On the other hand, informal feedback received from farmers and extension workers suggests that NSIC Rc 222 has performed well since it was released. So, we can also use this see with your own eyes or hear from others information for making our decision. Perhaps that is also what many farmers do.


About the Author

Dr. Achim Dobermann

Dr. Achim Dobermann

Achim is a soil scientist and agronomist with 25 years experience working in Asia, North America and Europe. He is recognized internationally as an authority on science and technology for food security and sustainable management of the world's major cereal cropping systems. He has authored or co-authored over 250 scientific papers and two books on nutrients in rice and has received numerous awards from various academic, government and industry organizations. He is a Fellow of the American Society of Agronomy and a Fellow of the Soil Science Society of America.

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