Azmi Man

Seeding method and rate influence on weed suppression in aerobic rice

-2 (SR400); and two weed control levels were established as weedy (W) and weed free (F) in a factorial RCBD with four replications. Twenty (20) weed species comprising eleven broadleaved, five grasses and four sedges were identified. Broadleaved weeds contributed more than 50% of the total dry matter. Weed density and dry weight decreased gradually with increased seeding rate, but were independent of methods. REW produced significantly higher grain yield compared with CBS. Among the seeding rates, SR300 produced the highest grain yield followed by SR200 and SR400. Weed free treatment performed better with a yield advantage of 23% over weedy treatment. Weed inflicted relative yield loss did not vary due to seeding methods or rates. Therefore, increasing seeding rate up to 300 seeds m -2 may be

Critical Period of Weed Control in Aerobic Rice

Critical period of weed control is the foundation of integrated weed management and, hence, can be considered the first step to design weed control strategy. To determine critical period of weed control of aerobic rice, field trials were conducted during 2010/2011 at Universiti Putra Malaysia. A quantitative series of treatments comprising two components, (a) increasing duration of weed interference and (b) increasing length of weed-free period, were imposed. Critical period was determined through Logistic and Gompertz equations. Critical period varied between seasons; in main season, it started earlier and lasted longer, as compared to off-season. The onset of the critical period was found relatively stable between seasons, while the end was more variable. Critical period was determined as 7–49 days after seeding in off-season and 7–53 days in main season to achieve 95% of weed-free yield, and 23–40 days in off-season and 21–43 days in main season to achieve 90% of weed-free yield. Since 5% yield loss level is not practical from economic view point, a 10% yield loss may be considered excellent from economic view point. Therefore, aerobic rice should be kept weed-free during 21–43 days for better yield and higher economic return.

Integration of agronomic practices with herbicides for sustainable weed management in aerobic rice

Till now, herbicide seems to be a cost effective tool from an agronomic view point to control weeds. But long term efficacy and sustainability issues are the driving forces behind the reconsideration of herbicide dependent weed management strategy in rice. This demands reappearance of physical and cultural management options combined with judicious herbicide application in a more comprehensive and integrated way. Keeping those in mind, some agronomic tools along with different manual weeding and herbicides combinations were evaluated for their weed control efficacy in rice under aerobic soil conditions. Combination of competitive variety, higher seeding rate, and seed priming resulted in more competitive cropping system in favor of rice, which was reflected in lower weed pressure, higher weed control efficiency, and better yield. Most of the herbicides exhibited excellent weed control efficiency. Treatments comprising only herbicides required less cost involvement but produced higher net benefit. On the contrary, treatments comprising both herbicide and manual weeding required high cost involvement and thus produced lower net benefit. Therefore, adoption of competitive rice variety, higher seed rate, and seed priming along with spraying different early-postemergence herbicides in rotation at 10 days after seeding (DAS) followed by a manual weeding at 30 DAS may be recommended from sustainability view point.

Distribution of weedy rice escape variants in Clearfield Rice Production System

Weedy rice is made up of the undesirable biotypes of rice with early and easy shattering characteristics, which causes a major yield reduction in direct-seeded rice in Malaysia. Thus, a series of survey were conducted in the selected Clearfield rice fields in the four townships, namely, Kampung Sungai Manik, FELCRA Seberang Perak, Kampung Mampas and Kampung Sungai Mati in the Peninsular Malaysia from April 2012 and April 2013 to study the dominance and abundance of weedy rice escaping Clearfield Production System (known as weedy rice escape). The survey was done according to the quantitative survey method by using standardized quadrat. A total of 1240 and 813 weedy rice escapes in dry/off season 2012 and main season 2012 were identified in all surveyed rice fields, respectively. Kampung Mampas indicated the highest dominance of weedy rice escapes, while FELCRA Seberang Perak recorded the lowest dominance in both the planting seasons. From the farmers’ complaint, poor rice management and weeding practices were the major factors that contributed to weedy rice escape in the fields.