INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY ISSN Print: 1560–8530; ISSN Online: 1814–9596 12–229/2013/15–2–191–199 http://www.fspublishers.org Full Length Article To cite this paper: Khaliq, A., A. Matloob, M.Z. Ihsan, R.N. Abbas, Z. Aslam and F. Rasool, 2013. Supplementing herbicides with manual weeding improves weed control efficiency, growth and yield of direct seeded rice. Int. J. Agric. Biol., 15: 191‒199 Supplementing Herbicides with Manual Weeding Improves Weed Control Efficiency, Growth and Yield of Direct Seeded Rice Abdul Khaliq 1* , Amar Matloob 1 , Muhammad Zahid Ihsan 1 , Rana Nadeem Abbas 1 , Zubair Aslam 1 and Fahd Rasool 1 1 Department of Agronomy, University of Agriculture, Faisalabad, Pakistan * For correspondence: khaliquaf@gmail.com Abstract Supplementing herbicide application with manual weeding in dry seeded rice fields can help control weeds more effectively. To test this assumption, pre and post-emergence herbicides applied either alone or supplemented with manual weeding were evaluated in a field study. Pendimethalin at 1137 g a.i. ha -1 as pre-emergence (0 DAS), bispyribac sodium, penoxsulam, pyrazosulfuron ethyl and ethoxysulfuron ethyl at 30, 15, 30 and 30 g a.i. ha -1 , respectively, as early post emergence (15 DAS) were applied alone and supplemented with manual weeding (hoeing/pulling, 30 DAS). A weedy check and manual weeding thrice (15, 30 and 45 DAS) were included for comparison. Data on weed dynamics and crop attributes were recorded following standard procedures. Weed density and biomass was significantly reduced under sole application of herbicides; nonetheless supplementing herbicides with manual weeding further reduced both of these attributes to a much larger extent. Bispyribac sodium recoded higher weed suppression when it was followed by manual weeding. Positive efficiency indices of different weed management treatments were also observed in the study. Significant improvement in rice growth and grain yield was recorded when herbicides were followed by manual weeding. Bispyribac sodium and ethoxysulfuron ethyl followed by manual weeding recorded similar grain yields. Rice growth and yield was negatively associated with weed density and biomass, and unrestricted weed growth incurred 75% yield loss in dry seed fine rice. Combination of bispyribac sodium and manual weeding was the best integrated weed management strategy to control weeds and enhance growth and yield of rice. © 2013 Friends Science Publishers Keywords: Direct seeding; Herbicides; Hoeing; Weed suppression; Rice growth; Grain yield Introduction Direct seeded rice (DSR) seems potential resource conservation strategy for achieving high water productivity and eliminating the time and edaphic conflicts in rice-wheat cropping system of Punjab (Khaliq et al., 2011a). An appropriate and timely weed management input has always been a prerequisite and key factor making DSR successful. Such a strategy is of utmost significance to secure yields and production costs involved as well as minimize negative effects on the quality of the produce. Timely and effective weed control has positive correlation with good crop stand and high yield of dry direct seeded rice. In DSR weeds emerge simultaneously with rice seedlings and competition starts at early stages when rice seedlings are too young to bear this competition. Depending upon types of species, density levels, age and emergence patterns of weeds, at least 3 manual weeding are required at appropriate growth stages of crop for ensuring good yields (Ampong-Nyarko and De Datta, 1991). Manual weeding is difficult to pursue early in season as weeds are too small to be pulled out. Waiting weeds to reach sufficient size to be removed is unwise as significant and irreparable damage might have occurred by that time. Delay in first weeding also increases persons-day per ha due to increased weed biomass. Weather dependency and the presence of perennial weeds that fragment on pulling, is other crucial aspect limiting manual weeding (Rao et al., 2007). Mimicking certain grassy weeds and rice further abandons manual weeding early in the season. Mechanical weeding often lacks selectivity, and hence cannot be opted. Rice is most susceptible to weed competition during early growth stage (Rao et al., 2007; Khaliq and Matloob, 2011) and higher rice yields can only be realized if weeds are controlled earlier. Ideally, pre and early post-emergence herbicide application can help control weeds at these times. Singh et al. (2006) emphasized that both pre and post emergence herbicides, if properly used are quite effective in suppressing weeds in DSR Over the years, chemical weed control has expanded manifold in DSR and is likely to increase further in response to labor scarcity, rising wages and increased adoption of direct seeding. Unfortunately, indiscriminate use of herbicides is driving the agro- ecosystems towards declining species diversity and, in many situations to herbicide resistance (Powles and Yu, 2010; Mahajan et al., 2011). Singh (2008) found that continuous use of a single herbicide can produce quantitative changes in weed community composition in just five years.