Study points to earlier control of weedy rice in direct-seeded farms

Farmers using direct seeding may need to control weedy rice earlier than usual, after a study found that the weed gains its advantage before cultivated rice reaches its reproductive stage.

The Philippine Rice Research Institute (PhilRice)-led study found that weedy rice can outgrow cultivated rice because it emerges earlier, grows taller, produces more tillers, and develops larger and more highly branched roots.

Dr. Leylani M. Juliano, PhilRice lead researcher, said that these traits help weedy rice absorb more water and nutrients from the soil. The weed can also continue using sunlight efficiently to grow even when nutrients are limited, giving it a stronger chance to compete in direct-seeded fields.

She said understanding how the weed competes can guide researchers in improving the timing and design of management strategies, especially during the early stages of crop growth.

The study showed that weedy rice builds much of its advantage from the seedling stage until before the reproductive stage, when competition with cultivated rice can be especially critical.

In direct-seeded systems, rice seeds are sown directly in the field, allowing weedy rice and cultivated rice to grow at the same time. This makes early control important before the weed becomes harder to manage.

The findings may also support future rice breeding work by identifying useful traits, such as strong seedling vigor and expansive root systems, that could help cultivated rice compete better with weedy rice.

The study also showed that Philippine weedy rice biotypes, or types, are not all the same. While they generally showed strong competitive ability, they differed in how they responded to crop management practices, including fertilization.

Researchers also observed differences in the microorganisms found around the roots of weedy rice. These root-associated microorganisms may help explain how some weedy rice types adapt and compete in the field.

Juliano said the findings provide useful information for further research on weedy rice management, rice breeding, biotype detection, and soil-related technologies.

The study, titled “Enhanced Morpho-physiological Traits and Microbial Diversity Drive the Competitive Advantage of Weedy Rice in Direct-Seeded Rice Ecosystem,” was conducted by Juliano in collaboration with Dr. Analiza Henedina M. Ramirez, professor at the Institute of Weed Science, Entomology, and Plant Pathology of the University of the Philippines Los Baños.

The research received the Best Paper Award during the 58th Pest Management Council of the Philippines Anniversary and Annual Scientific Conference 2026 held in General Santos City.