Control of Weedy Rice Infestation by Enhancing Rice Establishment in Anaerobic Direct Seeding

Weedy rice or ‘padi angin’ is a serious threat to the rice industry of Malaysia. Its easy grain shattering characteristics has been reported to reduce rice yield up to 74%. The shift from transplanting techniques to direct seeding of planting rice has increased the weedy rice infestation. Preliminary study had shown that pre- treated rice seeds used in anaerobic seeding technique were able to out compete the growth of weedy rice and simultaneously increase the rice establishment. The objectives of this study were; a) to evaluate different rice seed germination enhancers in anaerobic (water) seeding, b) to evaluate seedling emergence in different water temperatures in anaerobic seeding and c) to evaluate rice establishment using pre-treated seeds and herbicide in controlling weedy rice in anaerobic seeding. Three rice seed varieties (MRQ 50, MR 167 and MR 219) were given treatments. The treatments tested were rice seeds soaked in water (control, T1); rice seeds coated with calcium peroxide (sodium silicate binding agent), [T2]; seeds treated with 1% peroxide base material [T3], seeds treated with 0.2% dilute acid [T4] and seeds treated with seaweeds [T5]. The seedling emergence was evaluated at three days after sowing (DAS) and the rice seedling growth was evaluated fourteen days after sowing (DAS) in glasshouse trials. The number of emerged seedlings for T3 was significantly higher for MR167 and MR219 compared to control at three DAS. However, there were no significant differences for MRQ 50 for emerged seedlings compared to control. Generally, there were no interaction effects between varieties and treatments tested for seedling height, root length and root surface area. T3 showed a significant increase of 7% for seedling height compared to control. However, the performance of T2 was inferior to the other seed treatments as well as control for all varieties tested. The seedling height, root length and root surface area of rice seedlings of T2 were reduced significantly to 27%, 38% and 90%, respectively compared to control at fourteen DAS. T4 and T5 performed the same as control for seedling height, root length and root surface area. In a laboratory study, pre-treated rice seeds were sown in soil –filled petri dishes and placed in water bath. Water level was maintained at 5 cm and temperatures were adjusted according to treatments (T1: 30°C, T2: 35°C, T3: 40°C and T4: 45°C). Seedling height increased significantly by 11% at 35°C compared to control (30°C). Water temperature of more than 40ºC significantly inhibited the rice seedling emergence and growth. In a glasshouse trial, the effect of pre-treated cultivated rice seeds and herbicide application on the tiller establishment of cultivated rice and weedy rice in aerobic (wet) and anaerobic (water) seeding were evaluated. There were no significant differences for herbicide effects on weedy rice tillers. However, seedling emergence of weedy rice at 14 DAS and tiller establishment at 45 DAS was significantly reduced in water seeding compared to wet seeding. In a field trial, pre-treated seeds were sown into divided plots, T1: wet seeding (control) and T2: water seeding and the weedy rice population and rice yield were evaluated at harvest. Water seeding technique significantly reduced weedy rice population almost 52% compared to control at 90 DAS. In this trial, farmer’s received a surplus in yield using water seeding technique compared to wet seeding technique as water seeding increased net rice yield by 15% (almost one ton/ha). The use of pre-treated seeds for the anaerobic direct seeding technique had an advantage on seedling vigor that out competed the weedy rice growth, and increased the rice seeds viability