Research Article Rice Tolerance to Saflufenacil in Clomazone Weed Control Program

Transcription

1 Interntionl Journl of Agronomy Volume 2011, Article ID , 8 pges doi: /2011/ Reserch Article Rice Tolernce to Sflufencil in Clomzone Weed Control Progrm E. R. Cmrgo, 1, 2 S. A. Sensemn, 1 G. N. McCuley, 3 ndj.b.guice 4 1 Deprtment of Soil nd Crop Sciences, Texs A&M University, College Sttion, TX , USA 2 Conselho Ncionl do Desenvolvimento Científico e Tecnológico (CNPq), Brsíli, DF, Brzil 3 Texs AgriLife Reserch, Dvid Wintermnn Rice Reserch Center, Egle Lke, TX 77434, USA 4 BASF Corportion, Agriculturl Products Division, 6583 Min Street, Winnsboro, LA 71295, USA Correspondence should be ddressed to E. R. Cmrgo, edinlvo cmrgo@yhoo.com.br Received 22 July 2011; Accepted 20 September 2011 Acdemic Editor: Ptrick J. Trnel Copyright 2011 E. R. Cmrgo et l. This is n open ccess rticle distributed under the Cretive Commons Attribution License, which permits unrestricted use, distribution, nd reproduction in ny medium, provided the originl work is properly cited. This reserch ws conducted to evlute (1) rice tolernce to sflufencil pplied preemergence (PRE) nd postemergence (POST) nd (2) the combintion of sflufencil nd clomzone in light-textured soils. No injury from PRE ppliction of sflufencil ws observed in 2009, nd miniml injury for sflufencil lone ws observed in Injury s high s 68% ws observed with combintions of 505 g h 1 of clomzone pplied PRE nd 50 g h 1 of sflufencil pplied POST in 2009 erly evlutions. No interction between clomzone nd POST sflufencil rtes ws observed in Rice injury intensified with incresing rtes of sflufencil pplied POST. However, rice recovered with time for herbicide tretments pplied PRE nd POST in both yers. Consequently, rice yield ws not ffected by ny of the sflufencil rtes pplied either PRE or POST in clomzone weed control progrm. 1. Introduction Rice is stple food in numerous countries round the world. Rice consumption provides more clories thn ny other single food [1], serving dily s source of crbohydrte, proteins, lipids, vitmins, nd minerls [2, 3]. Riceyield is on n upwrd pth to chieve higher worldwide production s indicted by dt compiled in the lst ten yers by the Food nd Agriculture Orgniztion (FAO). Production incresed from 599 million tons in 2000 to 685 million tons in 2009 [4]. However, current supply trends re considered insufficient to trck projected demnd s the world popultion continues to rise [5]. Crop mngement will be even more importnt in production res in order to mintin nd/or expnd rice production. In the United Sttes, 1.07 million hectres were hrvested resulting in the production of 8.5 million tons of rice in the crop seson of 2011 [6]. The southern sttes of Arknss, Cliforni, Louisin, Mississippi, Texs, nd Missouri primrily contributed to this production. As weeds re one of the most importnt biologicl fctors limiting rice production [7], weed mngement is crucil to mximize rice yield potentil. Severl nnul grsses nd brodlef species re considered troublesome weeds in United Sttes rice regions [8]. In Arknss, the lrgest-producing stte, brnyrdgrss (Echinochlo crus-glli) ws reported to be the most problemtic grssy weed [9]. In the sme survey, clomzone ws described to be the most regulrly recommended preemergence (PRE) herbicide. Clomzone is reltively recent herbicide in rice, with commerciliztion occurring t the beginning of the century [10, 11]. This herbicide is metbolized to the 5-keto form of clomzone. The 5- keto form, which is the ctive herbicide, inhibits 1-deoxy-Dxylulose 5-phosphte synthse, key component to plstid isoprenoid synthesis [12]. Symptomology of clomzone includes bleching tht cn progress to necrosis [12, 13]. Weed mngement progrms with clomzone re widely utilized becuse of the low-cost nd effective nnul grss control [14]. Problemtic species such s brnyrdgrss nd brodlef signlgrss (Urochlo pltyphyll)cn be effectively controlled by clomzone [14, 15]. Also, occurrence of brnyrdgrss resistnt to propnil nd quinclorc [11, 16, 17]

2 2 Interntionl Journl of Agronomy hs contributed to considerble use of clomzone for weed mngement in rice. Although clomzone provides excellent control of grsses with the recommended rtes for rice, it is wek on brodlef nd sedge species [11]. Sflufencil is new herbicide currently registered for burndown nd PRE pplictions in winter cerels, soyben, corn, nd other crops [18 20]. This herbicide is highly effective on dicotyledon weeds with both residul nd contct ctivity [21, 22]. Consequently, sflufencil could broden the weed control spectrum in clomzone progrm by providing brodlef control. Improvement in brodlef weed control ws indicted s priority topic of reserch by survey conducted in Arknss [9]. Development of sflufencil for ricecouldgenertenewtooltohelpfrmerswithsomeof the specific brodlef weed control problems. However, crop tolernce nd herbicide interctions need to be evluted before sflufencil cn be used for weed control in rice. Sflufencil is member of the pyrimidinedione chemicl clss of herbicides, which inhibit the protoporphyrinogen IX oxidse (PPO) enzyme [23]. Crop response to sflufencil hs been studied for PRE pplictions in proso millet [24] nd leguminous crops [20], for postemergence (POST) pplictions in winter whet [25, 26], nd for PRE nd POST pplictions in corn [19], whet, brley, nd ots [18, 27] but currently no work hs been published regrding rice tolernce to this herbicide. Sflufencil cn provide brodlef weed control when pplied PRE or POST s Geier et l. [21] determined in greenhouse study with five weed species. Although control cn be chieved with PRE nd POST pplictions, crop injury my be limiting fctor to use sflufencil in weed control progrm with clomzone. PRE tnk-mixed ppliction my cuse higher rice injury especilly in light-textured soils. Sflufencil hs been demonstrted to be sfe in PRE pplictions for severl grss cropssuchscorn,whet,brleyndots[18, 19, 27], however, rice response hs not been investigted in lighttextured soils. The clomzone lbel excluded its pplictions in corse soils, but results obtined by Willinghm et l. [14] indicted tht it could be used without cusing significnt injury. Therefore, crop response to combintions of clomzone nd sflufencil in light-textured soils could indicte potentil for use of these herbicides in rice weed control progrm. POST ppliction of sflufencil is not currently recommended for in-crop weed control. Uncceptble injury nd yield reduction in brley, ots, nd whet were observed for POST pplictions of this mteril [18]. In corn, ppliction of sflufencil without djuvnt t spike (coleoptile hs reched the soil surfce) nd 2- to 3-lef stges resulted in cceptble tolernce; however, when djuvnt ws included with the herbicide, crop injury incresed resulting in yield loss [19]. Moreover, recent results in winter whet indicted sflufencil potentil for POST pplictions when used in combintion with 2,4-D mine without nonionic surfctnt [25, 26]. Also, wter-dispersible grnule formultion provided miniml injury in POST pplictions [26]. Hence, experimenttion with pplictions of sflufencil is needed to evlute the rice response to PRE nd POST tretments. Depending on crop tolernce, sflufencil used in combintion with clomzone could result in n lterntive tool for rice frmers providing comprehensive weed control progrm. Therefore, the objective of this reserch ws to evlute (1) rice tolernce to sflufencil pplied lone PRE nd POST nd (2) the combintion of sflufencil nd clomzone in light-textured soils. 2. Mteril nd Methods Two seprte experiments (PRE nd POST sflufencil) were conducted during 2009 nd 2010 t the Texs A&M AgriLife Reserch nd Extension Center locted t Egle Lke, TX. The soil ws Nd fine sndy lom (fine-lomy, siliceous, ctive, hyperthermic Albquic Hpludlfs) with 56.8% of snd, 33.6% of silt, 9.6% of cly, 0.8% of orgnic crbon, nd ph of 6.5. The re used to conduct the reserch ws in rice-fllow rottion where rice ws seeded every three yers. Therefore, studies were conducted in different fields within the reserch sttion ech yer. Soil ws disked to reduce vegettive biomss during the summer preceding estblishment of experiments. Prior to crop seeding in the spring, the seedbed ws cultivted gin nd the soil surfce ws grded to gurntee dequte field slope. The experiments were drill-seeded on April 15th, 2009, nd Mrch 31st, 2010 using the cultivr Cocodrie t the rte of 80 kg h 1. Emergence of rice occurred 11 dys fter seeding (DAS) the experiments in 2009 nd 8 DAS in In both yers, plots were formed by seven rows spced t 19 cm from ech other (1.3 m wide) nd mesuring 4.9 m long. Plots were seprte from ech other by 0.3-m lley. Before estblishing seson-long flood, rice fields were submerged nd subsequently drined t lest twice to introduce moisture in the soil. Seson-long flood ws initited 25 dys fter rice emergence (DAE) in 2009 nd 35 DAE in Triple superphosphte, potssium chloride, nd ure were pplied nd incorported in the soil prior to seeding t rte of 53 kg h 1 of P 2 O 5,K 2 O, nd N, respectively. Midseson nitrogen fertiliztion ws conducted t preflooding using 79 kg h 1 of nitrogen in the form of ure followed by 89 kg h 1 t pnicle differentition in the form of mmonium sulfte. The experimentl design ws rndomized complete block with fctoril rrngement. The tretments included combintions of three rtes of clomzone (0, 392, nd 505 g h 1, Commnd 3 ME, microencpsulted formultion, FMC Corportion, 1735 Mrket Street, Phildelphi, P 19103) nd five rtes of sflufencil (Shrpen, suspension concentrte formultion, BASF Corportion, 26 Dvis Drive, Reserch Tringle Prk, NC ). In the experiment with PRE pplictions of sflufencil, rtes were 0, 25, 50, 100, nd 200 g h 1. Rtes for POST pplictions of sflufencil were 0, 12.5, 18.75, 25, nd 50 g h 1.Tretments were replicted four times. Clomzone tretments were pplied immeditely fter rice seeding in both experiments. Clomzone nd sflufencil rtes were tnk-mixed in the experiment with PRE pplictions. In the study with POST pplictions of sflufencil, tretments were pplied t the 4- to 6-lef stge (V4-V6, ccording to Counce et l. [28]). Methylted seed oil (Methylted spry oil, blend of distilled

3 Interntionl Journl of Agronomy 3 methyl esters nd nonionic surfctnts, Helen Chemicl Compny, 225 Schilling Blvd., Suite 300, Collierville, TN 38017) t 1% v/v ws included in POST pplictions. Clomzone tretments provided effective control of grssy weeds. Consequently, tretments tht did not receive clomzone ppliction were mintined grss-free by pplying propnil plus quinclorc. In 2009, propnil (4485 g h 1 ) nd quinclorc (560 g h 1 ) were pplied t the 4- to 6-lef stge of rice (V4-V6) due to rinfll events tht delyed erlier plcement of these herbicides. In 2010, ppliction ws conducted t 2- lef stge (V2) using 3364 g h 1 of propnil nd 560 g h 1 of quinclorc. Tretment pplictions were performed using boom equipped with three fltfn nozzles (Teejet XR11002, Sprying Systems Co., P.O. Box 7900, Wheton, IL 60188) spced 50 cm prt. The boom ws coupled to CO 2 -pressurized bckpck spryer clibrted to deliver 140 L h 1 of spry solution t 172 kp. The dy before estblishment of the seson-long flood, mintennce pplictions were performed in ll plots using trctor spryer. In 2009, hlosulfuron-methyl (67 g h 1 )pluszetcypermethrin (28 g h 1 ) were used to control sedges nd insects, respectively. Only the insecticide zet-cypermethrin (28 g h 1 ) ws spryed in Rice injury ws estimted visully using scle of 0 to 100%, where 0 = no rice injury nd 100 = rice deth. Visul ssessments were conducted t 10, 22, 32 nd 38 DAE for PRE ppliction of sflufencil. In 2010, the first evlution ws conducted t 15 DAE insted of 10 DAE. Therefore, dt collected t 10 nd 15 DAE were used for sttisticl nlysis of combined yers. In the experiments with POST tretment of sflufencil, injury ws reported t 3, 8, 18 nd 24 dys fter sflufencil ppliction (DAA) in 2009 nd t 6, 12, 19 nd 24 DAA in For sttisticl nlysis of combined yers, dt were pired ccording to the ssessment order of ech yer. Therefore, results from 3 nd 6 DAA were considered the first evlution, s well s the dt from 8 nd 12 DAA were used for the second evlution. This pproch ws followed until the lst injury rting. Rice heding ws determined to be the dy in which more thn 50% of the plnts hd the pnicle emerged from the lef sheth [28]. Rice fields were drined before hrvesting t 100 DAE in 2009 nd 110 DAE in Four plot rows were hrvested with mechnicl hrvester when grin moisture ws pproximtely 20%. Hrvested smples were weighed nd moisture meter ws used to determine the moisture content of individul smples. Finl grin yield ws djusted to 12% moisture nd converted to kg h 1. Subsequently, sub-smple ws removed, dried nd used to determine milling yield. Dried smples were processed using ricemilling mchine (Zccri rice-testing, model PAZ/1-DTA, Indústri Mchin Zccri S/A, Ru Lrnjl, 180, Limeir, São Pulo, Brzil ). All dt were subjected to nlysis of vrince (ANOVA) using the PROC MIXED procedure of SAS (SAS 9.2 Softwre, SAS Institute Inc., 100 SAS Cmpus Drive, Cry, NC ). Crop injury dt were subjected to rcsine squre-root trnsformtion prior to nlysis. Subsequently, homogeneity nd normlity of vrince were verified using Brtlett s nd Shpiro-Wilk s Test. Dt were combined within yers, therefore vrinces were prtitioned into rndom effects (yers, blocks within yers nd yers by tretment interctions) nd fixed effects (clomzone rtes, sflufencil rtes nd their interctions). Results were combined when interction of yers by tretments were not significnt. Mens for significnt effects were seprted using Tukey s Test (P 0.05). 3. Results nd Discussion 3.1. Rice Injury Sflufencil Applied Preemergence. Sflufencil rte by clomzone rte by yer interction ws demonstrted by ANOVA t the first (10/15 DAE) nd second (22 DAE) ssessments in the study with PRE pplictions of sflufencil (Tble 1). Consequently, results were presented for ech yer seprtely. In 2009, no interction between clomzone nd sflufencil rtes ws observed t 10 nd 22 DAE. No injury from PRE ppliction of sflufencil lone ws observed in 2009 (Tble 2). Injury incresed following rte increments of clomzone, but it did not surpss 11% for dt collected t 10 DAE. Clomzone pplied t 392 g h 1 cn be used s reference rte since it provided effective weed control while being sfe to rice in sndy soils [14]. Injury from clomzone diminished over time with less thn 3% observed t the lter evlution (22 DAE). In 2010, no clomzone by sflufencil interction ws detected in the first ssessment (15 DAE). A similr trend for clomzone injury ws observed in 2010 when compred with the first ssessment of 2009, but higher vlues (up to 31%) were reported in the second yer. Reltively higher clomzone injury my be relted with plnts exposure to lower tempertures in the beginning of the growing seson due to n erlier plnting dte in For sflufencil rtes, greter injury ws observed t the highest rte (200 g h 1 ) when compred with the lower rtes (25 to 100 g h 1 ). However, injury observed t 200 g h 1 ws not different thn the plots untreted with sflufencil. These results re ssocited with vribility of clomzone when dt were verged cross sflufencil rtes. A significnt clomzone nd sflufencil rte interction occurred for the second evlution of 2010 (22 DAE). Injury ws significntly different for sflufencil tretments t 100 nd 200 g h 1,howeveritws<6% (Tble 3). Necrotic tissue ws visible in the lower region of the plnt stem when sflufencil ws pplied lone. In the tretments with PRE combintions of clomzone nd sflufencil greter injury ws observed when the highest rtes of the two herbicides were tnk-mixed. Injury mong sflufencil rtes rnged from 10 to 23% t 392 g h 1 of clomzone nd from 20 to 40 t 505 g h 1 of clomzone. At the intermedite rte of clomzone (392 g h 1 ), no differences were detected from 0 up to 100 g h 1 of sflufencil, demonstrting potentil for use of these two herbicides. For the highest rte of clomzone, the tretment with no ppliction of sflufencil hd sttisticlly similr injury compred with the highest rte of sflufencil. Vribility within the highest rte of clomzone my explin these

4 4 Interntionl Journl of Agronomy Tble 1: P vlues for multiple ssessments of visible injury, yield, nd whole grin for preemergence (PRE) nd postemergence (POST) pplictions of sflufencil. Experiment PRE POST Source of vrition Pr > F for nlyzed prmeters Visible injury 1st 2nd 3rd 4th Yield Whole grin Yer (Y) < < < < < < Block (yer) < Clomzone (C) < < < C Y < < < Sflufencil (S) < < S Y < C S C S Y Yer (Y) < < < < < < Block (yer) < Clomzone (C) < < C Y Sflufencil (S) < < < < S Y < < < < C S < < C S Y < < Represents the 1st, 2nd, 3rd, nd 4th ssessment evlutions for visible injury. Tble 2: Rice (Oryz stiv L.) visible injury t 10 dys fter emergence (DAE) nd 22 DAE in 2009 nd 15 DAE in 2010 in response to sflufencil nd clomzone pplied preemergence. Sflufencil results were verged cross clomzone rtes, nd clomzone results were verged cross sflufencil rtes. Sflufencil rtes (g h 1 ) Visul injury DAE 22 DAE 15 DAE % 0 5 b 2 b 21 b c b b b Clomzone rtes (g h 1 ) 0 d 0c 2b 1c b 1 b 24 b Injury ws estimted visully using scle of 0 to 100% where 0 = no rice injury nd 100 = rice deth. b Mens were not different ccording to F-test t P c Mens followed by different letter re significntly different ccording to the Tukey s test (P 0.05). d Plots tht did not receive clomzone were treted with propnil plus quinclorc. results. Clomzone plus sflufencil pplied PRE resulted in typicl folir bleching followed by necrosis. Additionlly, necrosis of the lower region of the stem ws cused by the inhibition of the PPO enzyme by sflufencil (Figure 1(c)). Tble 3: Rice (Oryz stiv L.) visible injury t 22 DAE in response to sflufencil nd clomzone pplied preemergence. Dt represent n interction between rtes of sflufencil nd clomzone in Sflufencil rtes (g h 1 ) Visul injury Clomzone rtes (g h 1 ) 0 b % 0 0c c 15 bc 25 b 25 0 c 15 bc 20 b 50 0 c 10 c 20 b b 18 b 20 b Injury ws estimted visully using scle of 0 to 100% where 0 = no rice injury nd 100 = rice deth. b Plots tht did not receive clomzone were treted with propnil plus quinclorc. c Mens followed by different letter within column re significntly different ccording to the Tukey s test (P 0.05). Although injury ws observed t the highest rtes of sflufencil pplied PRE s well s when it ws combined with clomzone in 2010, rice plnts were ble to recover over time. In lter evlutions, dt verged cross yers nd clomzone rtes demonstrted less thn 3% nd 2% injury t 32 nd 38 DAE, respectively (dt not shown). Rice ws consistently tolernt to PRE pplictions of sflufencil lone up to 200 g h 1 in both yers of study. Other summer nd winter grss crops demonstrted the potentil of sflufencil for PRE pplictions. Summer crops such s corn tolerted up to 200 g h 1 of sflufencil pplied PRE [19]. In proso millet, PRE ppliction of 50 nd

5 Interntionl Journl of Agronomy 5 () (b) (c) (d) Figure 1: Rice symptoms from clomzone lone (b), clomzone plus sflufencil pplied preemergence (c), nd postemergence (d). Untreted check is represented in box (). Pictures were tken in different rice stges. 100 g h 1 of sflufencil reduced plnt stnd comprtively with the untreted check; however, rtes did not cuse yield reduction [24]. Winter cerels such s whet, brley, nd ots demonstrted crop tolernce to sflufencil up to 100 g h 1 [18]. In study conducted by Knezevic et l. [27], sflufencil rtes up to 400 g h 1 did not cuse injury or yield reduction in winter whet. In rice, sflufencil seems to be potentilly useful nd sfe herbicide for PRE ppliction with clomzone Sflufencil Applied Postemergence. In the study with POST ppliction of sflufencil, interction mong yers, clomzone, nd sflufencil rtes ws verified by ANOVA for ll evlutions, resulting in nlysis of dt by individul yers. In 2009, interction between rtes of sflufencil nd clomzone ws observed throughout ll ssessment timings. Rice injury ws observed to be higher with combintions of the highest rte of sflufencil (50 g h 1 ) nd clomzone tretments (Tble 4). In evlutions conducted 3 dys fter POST ppliction (DAA), injury s high s 68% ws observed with the combintion of 505 g h 1 of clomzone nd 50 g h 1 of sflufencil. The mode of ction of these herbicides my explin the interction observed where initil injury from clomzone could deplete the crotenoid pool leding to more intense ction from the rdicls produced by inhibition of PPO (sflufencil). POST ppliction of sflufencil fter sprying clomzone PRE resulted in necrosis on the upper leves of the rice plnts by ction of sflufencil. At the sme time, lower leves were still displying bleching symptoms from clomzone (Figure 1(d)). Rice injury intensified with incresing rtes of sflufencil lone, reching up to 18% in the initil rting of Appliction of propnil (4485 g h 1 ) nd quinclorc (560 g h 1 ) to control grss weeds in plots tht did not receive clomzone cused 5% injury even in the tretment without sflufencil POST ppliction. Combintions of the intermedite rte of clomzone (392 g h 1 ) nd rtes of sflufencil up to 25 g h 1 pplied POST resulted in 25% injury. The initil injury observed from POST ppliction of sflufencil lone or following PRE ppliction of clomzone could be cceptble s long s rice plnts recover, nd rice yield would be not negtively ffected by erly phytotoxicity.

6 6 Interntionl Journl of Agronomy Tble 4: Visible rice(oryz stiv L.) injury t 3, 8, 18, nd 24 dys fter ppliction (DAA) in response to postemergence ppliction (4- to 6-lef stge, V4-V6) of sflufencil following preemergence ppliction of clomzone. Dt represents n interction between rtes of sflufencil nd clomzone for experiment conducted in Sflufencil rtes (g h 1 ) Visul injury 3 DAA 8 DAA 18 DAA 24 DAA Clomzone rtes (g h 1 ) Clomzone rtes (g h 1 ) Clomzone rtes (g h 1 ) Clomzone rtes (g h 1 ) 0 b % 0 5b c 1d 3d 4b 0c 1d 0 d 0b 0b 0 d 0b 0c b 11c 13c 10b 6b 8c 0 0b 0b 0 1b 0c b 25 b 16 c 8 b 15 b 11 c 6 3 b 0 b bc b 24 bc 35 b 10 b 15 b 25 b 6 3 b b 5 b Injury ws estimted visully using scle of 0 to 100% where 0 = no rice injury nd 100 = rice deth. b Plots tht did not receive clomzone were treted with propnil plus quinclorc. c Mens followed by different letter within column re significntly different ccording to the Tukey s test (P 0.05). d Mens were not different ccording to F-test t P In evlutions conducted t 8 DAA, rice response to herbicide tretments followed similr trend s initil evlution, but overll intensity of injury hd lredy diminished over 5-dy intervl. In subsequent evlutions, rice injury decresed significntly to < 14% nd < 9% for ll tretments during ssessments performed 2 nd 3 weeks fter initil evlution. No significnt differences were observed mong sflufencil tretments lone t lter rtings. In 2009, nitrogen ppliction nd seson-long flood were introduced in the experimentl re t 10 DAA. These mngement prctices likely helped the injured rice overcome herbicide symptoms more rpidly. No interction between clomzone nd sflufencil ws verified in In the evlution t 6 DAA, injury from sflufencil verged cross clomzone rtes ws s high s 26% t 50 g h 1 of sflufencil, but < 13% in the remining sflufencil tretments (Tble 5). In the subsequent evlution conducted t 12 DAA, significntly greter injury ws detected t the highest rte of sflufencil (9%). However, no differences were observed from 0 to 25 g h 1 of sflufencil. Injury ws bsent in ll plots for evlutions conducted t 19 nd 24 DAA. POST ppliction of sflufencil is not currently recommended in row crops. Work by others demonstrted injury s high s 76% in winter cerels from POST ppliction of sflufencil remining s high s 35% lmost one month fter tretment [18]. Corn demonstrted cceptble tolernce to sflufencil pplied without djuvnt t spike nd 2- to 3- lef stges; however, ddition of djuvnt incresed injury nd cused yield loss, especilly when pplictions were mde t the 2- to 3-lef stge [19]. More recently, results obtined in winter whet indicted lower injury from POST pplictions of sflufencil in combintion with 2,4-D mine without nonionic surfctnt when compred with sflufencil lone [25]. In this study, injury occurred with POST ppliction of sflufencil lone or in weed control progrm with clomzone in light-textured soils, but rice plnts seemed to recover from erly phytotoxicity. Sflufencil pplictions mde prior to nd fter emergence did not ffect heding in either yer. Therefore, rice Tble 5: Rice (Orz stiv L.) visible injury t 6 nd 12 dys fter ppliction (DAA) in response to postemergence ppliction (4- to 6-lef stge, V4-V6) of sflufencil following preemergence ppliction of clomzone. Sflufencil results were verged cross clomzone rtes, nd clomzone results were verged cross sflufencil rtes. Visul injury Sflufencil rtes (g h 1 ) DAA 12DAA % 0 3d b 0b c 0 b bc 1 b b 2 b Clomzone rtes (g h 1 ) 0 c 9b 2 d b Injury ws estimted visully using scle of 0 to 100% where 0 = no rice injury nd 100 = rice deth. b Mens followed by different letter re significntly different ccording to the Tukey s test (P 0.05). c Plots tht did not receive clomzone were treted with propnil plus quinclorc. d Mens were not different ccording to F-test t P development ws not ffected by crop injury observed erly in the seson from sflufencil nd clomzone tretments. Fifty percent heding ws observed t 75 nd 82 DAE in 2009 nd 2010, respectively. This is in the norml rnge for very erly mturity cultivr such s Cocodrie [29] Grin Yield nd Qulity. No interction mong herbicide tretments nd yers ws reveled by ANOVA; therefore, results were combined over yers. Also, no interction mong clomzone nd sflufencil ws detected from pooled dt during the 2-yer study. Consequently, grin yield ws presented ccording to sflufencil rtes. Rice yield ws

7 Interntionl Journl of Agronomy Sflufencil rte (g h 1 ) Sflufencil rte (g h 1 ) Grin yield (t h 1 ) Grin yield (t h 1 ) () (b) Figure 2: Grin yield (t h 1 ) in response to preemergence () nd postemergence (b) ppliction of sflufencil following preemergence ppliction of clomzone. Dt were verged cross clomzone rtes. Mens were not different ccording to F-test t P not significntly ffected by sflufencil PRE nd POST pplictions (Figure 2). Grin yield rnged from 8.05 to 8.58 t h 1 mong the PRE rtes of sflufencil. For the POST rtes of sflufencil, rice yield ws between 7.78 to 8.21 t h 1. Although injury of lmost 70% occurred erly in the seson from combintions of clomzone PRE nd sflufencil POST pplictions, rice yield ws not dversely ffected in ny sflufencil tretment. Contrdictory, injury from POST ppliction of sflufencil in corn [19], brley, ots, nd whet [18] nd winter whet [27] significntly reduced yield. Differences in intrinsic tolernce nd crop mngement ssocited with rice production such s nitrogen fertiliztion followed by estblishment of flooding my be fvoring rice recovery from clomzone nd sflufencil injury. Whole grin percentge ws similr mong sflufencil rtes in PRE nd POST ppliction studies. Whole grin yield ws higher thn 60% for ll rtes of sflufencil pplied PRE nd POST in the verge of two yers of dt (dt not shown). This would be n expected result considering tht no dely in heding ws reported from herbicides tretments. In summry, rice ws consistently tolernt to PRE pplictions of sflufencil lone up to 200 g h 1 in both yers of study. Combintion of sflufencil up to 100 g h 1 with n intermedite rte of clomzone (392 g h 1 )cnbe potentil mixture for PRE ppliction in rice regrding crop tolernce. Greter injury occurred when sflufencil ws pplied POST t 50 g h 1 following clomzone. However, sflufencil rtes up to 25 g h 1 pplied POST following n intermedite rte of clomzone resulted in initil rice injury tht rpidly diminished. Rice yield ws not dversely ffected by sflufencil rtes pplied either PRE or POST in clomzone weed control progrm in light-textured soils. Acknowledgments The uthors thnk the CNPq, Conselho Ncionl de Desenvolvimento Científico e Tecnológico, Brzil, for the student scholrship nd BASF Corportion for funding the reserch. They would like to cknowledge John Hrden, Steve Bowe, Tom Holt, nd Rex Liebl for their vluble contributions during the orgniztion of the studies nd for the opportunity to work with the chemicl, nd Benjmin McKnight, Aron Turner, Jck Vwter, nd Json Smford for their ssistnce during the conduction of the experiments. References [1] D. Kennedy, The importnce of rice, Science, vol. 296, no. 5565, p. 13, [2] B. Lin, Z. Tn, G. Xio et l., Evlution of compositionl nd nutritionl equivlence of geneticlly modified rice to conventionl rice using in situ nd in vitro techniques, Journl of the Science of Food nd Agriculture, vol. 89, no. 9, pp , [3] M.Wlter,E.Mrchezn,ndL.A.DeAvil, Rice:composition nd nutritionl chrcteristics, Cienci Rurl, vol. 38, no. 4, pp , [4] FAO, Food nd Agriculture Orgniztion of United Ntions, Sttistics, FAOSTAT-Agriculture, Production, Crops, 2011, [5] M. Aureus nd L. Reyes, Rice for future genertions, Rice Tody, pp , [6] USDA, United Sttes Deprtment of Agriculture, Producers, Dt nd Sttistics, Reports by Commodity, 2011, by Subject/index.php. [7] K. Sito, Weed pressure level nd the correltion between weed competitiveness nd rice yield without weed competition: n nlysis of empiricl dt, Field Crops Reserch, vol. 117, no. 1, pp. 1 8, [8] T. Webster, Weed survey-southern sttes, Proceedings Southern Weed Science Society, vol. 53, pp , [9] J.K.Norsworthy,N.R.Burgos,R.C.Scott,ndK.L.Smith, Consultnt perspectives on weed mngement needs in Arknss rice, Weed Technology, vol. 21, no. 3, pp , [10] H. R. Mitchell nd E. V. Gge, Commnd 3 ME: weed control in southern rice, Proceedings Southern Weed Science Society, vol. 52, p. 186, 1999.

8 8 Interntionl Journl of Agronomy [11] R. E. Tlbert nd N. R. Burgos, History nd mngement of herbicide-resistnt brnyrdgrss (Echinochlo crus-glli)in Arknss rice, Weed Technology, vol. 21, no. 2, pp , [12] S. A. Sensemn, Herbicide Hndbook, Weed Science Society of Americ, Lwrence, Kn, USA, 9th edition, [13] E. F. Scherder, R. E. Tlbert, nd S. D. Clrk, Rice (Oryz stiv) cultivr tolernce to clomzone, Weed Technology, vol. 18, no. 1, pp , [14] S. D. Willinghm, N. R. Flkenberg, G. N. McCuley, nd J. M. Chndler, Erly postemergence clomzone tnk mixes on corse-textured soils in rice, Weed Technology, vol. 22, no. 4, pp , [15] E. P. Webster, F. L. Bldwin, nd T. L. Dillon, The potentil for clomzone use in rice (Oryz stiv), Weed Technology, vol. 13, no. 2, pp , [16] A. M. Bltzr nd R. J. Smith Jnr, Propnil-resistnt brnyrdgrss (Echinochlo crus-glli) control in rice (Oryz stiv), Weed Technology, vol. 8, no. 3, pp , [17] M. S. Mlik, N. R. Burgos, nd R. E. Tlbert, Confirmtion nd control of propnil-resistnt nd quinclorc-resistnt brnyrdgrss (Echinochlo crus-glli) in rice, Weed Technology, vol. 24, no. 3, pp , [18] P. H. Sikkem, C. Shropshire, nd N. Soltni, Tolernce of spring brley (Hordeum vulgre L.),ots (Aven stiv L.) nd whet (Triticum estivum L.) to sflufencil, Crop Protection, vol. 27, no. 12, pp , [19] N. Soltni, C. Shropshire, nd P. H. Sikkem, Response of corn to preemergence nd postemergence pplictions of sflufencil, Weed Technology, vol. 23, no. 3, pp , [20] N. Soltni, C. Shropshire, nd P. H. Sikkem, Sensitivity of leguminous crops to sflufencil, Weed Technology, vol. 24, no. 2, pp , [21] P. W. Geier, P. W. Sthlmn, nd L. D. Chrvt, Dose responses of five brodlef weeds to sflufencil, Weed Technology, vol. 23, no. 2, pp , [22] R.A.Liebl,H.Wlter,S.J.Bowe,T.J.Holt,ndD.E.Westberg, BAS 800H: new herbicide for preplnt burndown nd preemergence dicot weed control, Proceedings Weed Science Society of Americ, vol. 48, p. 120, [23] K. Grossmnn, R. Niggeweg, N. Christinsen, R. Looser, nd T. Ehrhrdt, The herbicide sflufencil (Kixor) is new inhibitor of protoporphyrinogen IX oxidse ctivity, Weed Science, vol. 58, no. 1, pp. 1 9, [24] D. J. Lyon nd A. R. Kniss, Proso millet tolernce to sflufencil, Weed Technology, vol. 24, no. 3, pp , [25] J. C. Frihuf, P. W. Sthlmn, nd P. W. Geier, Winter whet nd weed response to postemergence sflufencil lone nd in mixtures, Weed Technology, vol. 24, no. 3, pp , [26] J. C. Frihuf, P. W. Sthlmn, P. W. Geier, nd D. E. Peterson, Winter nnul brodlef weeds nd winter whet response to postemergence ppliction of two sflufencil formultions, Weed Technology, vol. 24, no. 4, pp , [27] S. Z. Knezevic, A. Dtt, J. Scott, nd L. D. Chrvt, Tolernce of winter whet (Triticum estivum L.) to pre-emergence nd post-emergence ppliction of sflufencil, Crop Protection, vol. 29, no. 2, pp , [28] P. A. Counce, T. C. Keisling, nd A. J. Mitchell, A uniform, objectives, nd dptive system for expressing rice development, Crop Science, vol. 40, no. 2, pp , [29] M. O. Wy, Texs Rice Production Guidelines, Texs AgriLife Reserch, Texs AgriLife Extension, nd United Sttes Deprtment of Agriculture, Beumont, Tex, USA, 2010.

9 Veterinry Medicine Interntionl Scientific Interntionl Journl of The Scientific World Journl Journl of Food Science Botny Interntionl Journl of Interntionl Journl of Ecology Agronomy Submit your mnuscripts t Applied & Environmentl Soil Science Interntionl Journl of Biodiversity Journl of Interntionl Journl of Forestry Reserch Biotechnology Reserch Interntionl Nutrition nd Metbolism Interntionl Journl of Evolutionry Biology Interntionl Journl of Interntionl Journl of Cell Biology Interntionl Journl of Genomics Interntionl Journl of Plnt Genomics Advnces in Agriculture Psyche Microbiology