Lower global warming potential and higher yield of wet direct-seeded rice in Central China

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1 Lower glol wrming potentil nd higher yield of wet direct-seeded rice in Centrl Chin Ye To, Qin Chen, Shoing Peng, Weiqin Wng, Lixio Nie To cite this version: Ye To, Qin Chen, Shoing Peng, Weiqin Wng, Lixio Nie. Lower glol wrming potentil nd higher yield of wet direct-seeded rice in Centrl Chin. Agronomy for Sustinle Development, Springer Verlg/EDP Sciences/INRA, 2016, 36 (2), pp.24. < /s >. <hl > HAL Id: hl Sumitted on 2 Jun 2017 HAL is multi-disciplinry open ccess rchive for the deposit nd dissemintion of scientific reserch documents, whether they re pulished or not. The documents my come from teching nd reserch institutions in Frnce or rod, or from pulic or privte reserch centers. L rchive ouverte pluridisciplinire HAL, est destinée u dépôt et à l diffusion de documents scientifiques de niveu recherche, puliés ou non, émnnt des étlissements d enseignement et de recherche frnçis ou étrngers, des lortoires pulics ou privés.

2 Agron. Sustin. Dev. (2016) 36: 24 DOI /s RESEARCH ARTICLE Lower glol wrming potentil nd higher yield of wet direct-seeded rice in Centrl Chin Ye To 1 & Qin Chen 1 & Shoing Peng 1 & Weiqin Wng 1 & Lixio Nie 1,2 Accepted: 22 Mrch 2016 /Pulished online: 7 April 2016 # INRA nd Springer-Verlg Frnce 2016 Astrct Direct-seeded rice is promising option ecuse it sves wter nd lor, nd it increses productivity. Nonetheless, few studies hve evluted the trnsition from trditionlly trnsplnted rice to direct-seeded rice. Here we compred yield, wter productivity, nd greenhouse gs emissions of dry direct-seeded rice, wet direct-seeded rice, nd trnsplnted rice in Centrl Chin in 2014 nd We grew four rice cultivrs: Hunghuzhn, LvdoQ7, Ynglingyou6, nd Ylingyou1. We mesured grin yield, yield components, wter consumption, wter productivity, nd greenhouse gs emissions. Our results show tht the grin yield of wet direct-seeded rice ws 10.8 % higher thn tht of trnsplnted rice, when verged cross cultivrs nd oth yers. Grin yield of dry direct-seeded rice nd trnsplnted rice ws similr. Wter productivity of dry direct-seeded rice ws 11.6 % higher thn tht of trnsplnted rice. Wter productivity of wet direct-seeded rice ws 13.4 % higher thn tht of trnsplnted rice. Glol wrming potentil ws 76.2 % lower for dry direct-seeded rice nd 60.4 % lower for wet direct-seeded rice thn for trnsplnted rice. Wet direct-seeded rice ws found to e more susceptile to lodging thn dry direct-seeded rice nd trnsplnted rice. Overll, wet direct-seeded rice is the est system for Centrl Chin due to higher grin yield nd wter * Lixio Nie nielixio@mil.hzu.edu.cn 1 2 Ntionl Key Lortory of Crop Genetic Improvement, MOA Key Lortory of Crop Ecophysiology nd Frming System in the Middle Reches of the Yngtze River, College of Plnt Science nd Technology, Huzhong Agriculturl University, Wuhn, Huei , Chin Huei Collortive Innovtion Center for Grin Industry, Yngtze University, Jingzhou, Huei , Chin productivity nd lower glol wrming potentil. Dry directseeded rice my lso e suitle for some regions where wter is scrce for soil puddling during lnd preprtion. Keywords Dry direct-seeded rice. Wet direct-seeded rice. Trnsplnted rice. Grin yield. Wter productivity. Greenhouse gs emission 1 Introduction Glolly, wter is ecoming n incresingly scrce resource (Kumr nd Ldh 2011). Trnsplnted rice, which refers to the process of trnsplnting rice seedlings from nursery eds to puddled soil, is the mjor rice crop estlishment method in Chin (Peng et l. 2009). However, trnsplnted rice is lwys considered to wste wter, s lrge quntities of wter re consumed during the lnd preprtion nd frming processes (Boumn 2009). Compred with other cerel crops such s whet nd mize, trnsplnted-flooded rice consumes two or three times more wter (Brker et l. 1998;CrrigerndVllée 2007). Lrge mounts of wter re required for puddling, most of which is wsted through surfce evportion nd percoltion (Frooq et l. 2011). Furthermore, the wter use efficiency of trnsplnted rice is low. It hs een reported tht with the consumption of 1 m 3 wter, less thn 1 kg grins were produced (Boumn 2009). Another fctor tht is severe ostcle for rice production in Chin is tht the high demnd for lor during trnsplnting severely conflicts with the lor shortge in the Chinese griculturl system. Thus, the trditionlly trnsplnted rice, which hs high lor demnd, is no longer suitle for sustinle development in Chin, suggesting tht mechniztion is the only wy to resonly nd effectively solve these prolems. However, the mechniztion level for trnsplnted rice is still low. Although mechniztion during

3 24 Pge 2 of 9 Agron. Sustin. Dev. (2016) 36: 24 rice hrvesting hs een widely dpted y rice frmers, sowing mechniztion is still lgging. It hs een reported tht mechniztion levels for rice during lnd preprtion nd hrvesting reched 91 nd 70 %, respectively, y the end of 2011, ut the mechniztion level during rice estlishment (including seed sowing nd trnsplnting) could only rech 26 % (Chen et l. 2015). This is minly due to the complexity of trnsplnting. For exmple, pddy fields re smll nd scttered, which is not suitle for mchinery opertion. Poor seedling qulity nd high rte of vcncy on hills lso restrict the mechnicl trnsplnttion of rice. In contrst, direct-seeded rice, which refers to the process of directly sowing the seeds in the field insted of trnsplnting rice seedlings, hs een proposed to reduce wter requirements nd sve energy, nd works well with mechniztion for rice plnting. Mechnicl direct seeding of rice hs simpler steps compred with mechniclly trnsplnting rice. With the development of hericides, there is rising trend of using mechnicl direct seeding for rice in Chin (Wng et l. 2006). The following direct-seeding methods hve een suggested for rice in Chin: (1) dry direct-seeded rice, in which dry rice seeds re drilled or rodcsted on non-puddled soil fter dry tillge, zero tillge, or on rised ed, nd (2) wet direct-seeded rice, in which dry seeds or sprouted rice seeds re rodcst or sown in lines on wet nd puddled soil. Another principl method of direct-seeded rice is wter seeding, in which sprouted rice seeds re rodcst in soil withstnding wter (Kumr nd Ldh 2011). Previous studies hve compred the vrinces etween different types of direct-seeded rice nd trditionl trnsplnted rice for yield, wter use efficiency, nd estlishment methods. Generlly, the yield performnce of dry direct-seeded rice nd wet direct-seeded rice ws close to the yield of trditionl trnsplnted rice (Mitchell et l. 2004; Rickmn et l. 2001). Menwhile, direct-seeded rice required lower irrigtion wter due to fewer continuous flooded dys in the min field nd less wter use during lnd preprtion compred with trditionl trnsplnted rice. Zho et l. (2007) documented higher grin yields nd lower wter use for dry direct-seeded rice compred with trnsplnted rice. Agriculture is considered mjor nthropogenic source of CH 4 nd N 2 O, ccounting for 50 nd 60 % of totl CH 4 nd N 2 O emissions, respectively, in 2005 (Smith et l. 2007). Conventionlly trnsplnted rice contriutes lot to the emission of greenhouse gses (GHGs), prticulrly methne (CH 4 ) nd nitrous oxide (N 2 O). Rice pddies hve een identified s mjor source of CH 4, mounting to 11 % of glol totl nthropogenic CH 4 emissions (Smith et l. 2007). Furthermore, emission of GHGs from rice fields is highly sensitive to rice mngement prctices; there re differences in the mount of greenhouse gs emissions from different rice estlishment methods. Wssmnn et l. (2004) reported tht totl CH 4 emissions were reduced in direct-seeded rice fields compred with trnsplnted rice. Previous reserch hs lso indicted tht direct-seeded rice would simultneously decrese CH 4 ut enhnce N 2 O emissions (Shng et l. 2011). However, further studies re needed to updte our knowledge on CH 4 nd N 2 O emissions from different direct-seeded rice systems. With the dvntges of wter nd lor sving, incresing system productivity, nd mtching the development of new types of mechniztion equipment, direct-seeded rice hs een proposed s promising option for rice production. To dte, few studies hve een conducted to investigte the crop performnce of dry direct-seeded nd wet direct-seeded rice under well-wtered soil conditions. Centrl Chin is one of the lrgest rice plnting regions in Chin, where plnting res for direct-seeded rice is incresing rpidly. To evlute the potentil of shifting from trnsplnted rice to dry direct-seeded rice nd wet direct-seeded rice in terms of grin yield performnce, wter use efficiency, nd greenhouse gs emissions, two-yer field experiments were conducted for the three estlishment methods (Fig. 1). 2 Mteril nd methods 2.1 Study site The field experiments were conducted t the Zhougn Villge (29 51 N, E), Djin Town, Wuxue County, Huei Province, Chin, in 2014 nd In ech yer, soil smples were collected once from the upper 20 cm of the surfce efore the experiments were strted. The ph, orgnic mtter, totl nitrogen, ville phosphorus, nd extrctle potssium were 5.07, 21.0 g kg 1, 0.17 %, mg kg 1,nd 91.8 mg kg 1,respectively. 2.2 Experimentl design In this study, the following three estlishment methods were dopted: (1) dry direct-seeding rice, (2) wet direct-seeding rice, nd (3) trnsplnting rice. The following four indic rice cultivrs were used: (1) Hunghuzhn (inred), (2) LvdoQ7 (inred), (3) Ynglingyou6 (hyrid), nd (4) Ylingyou1 (hyrid), which re widely grown y rice frmers in Centrl Chin. The tretments were rndomly rrnged using splitplot design; the estlishment methods were ssigned in the min plots, nd cultivrs were ssigned in the su-plot (3.9 m 5.6 m) with four replictes. Soil in the dry directseeded rice plots ws dry-ploughed nd hrrowed without wter puddling, nd the dry seeds were sown mnully in rows with row spce of 25 cm t sowing rte of 60 kg h 1. Different from dry direct-seeded rice, oth wet direct-seeded rice nd trnsplnted rice plots were ploughed nd puddled efore seed sowing or trnsplnting. The sowing density nd rte in wet direct-seeded rice were the sme s in

4 Agron. Sustin. Dev. (2016) 36: 24 Pge 3 of 9 24 A fertilizer dose of 150:40:100 kg N:P:K h 1 ws pplied eqully to ll of the tretments. All of the P, one third of the N, nd hlf of the K were pplied s sl strter dose, while the residul N ws eqully split t the middle tillering stge nd the pnicle initition stge, nd the other 50 % of the potssium ws top-dressed during pnicle initition. Weeds, diseses, nd insects were intensively controlled during the entire growing seson in oth yers. 2.3 Dt collection Plnt growth, grin yield, nd yield components At the physiologicl mturity stge, 0.5 m 2 of plnts (two djcent rows nd 1 m in length for dry direct-seeded rice nd wet direct-seeded rice nd 15 hills for trnsplnted rice) were collected to determine the yield components, oveground iomss, nd hrvest index. The grin yield ws determined from smpling re of 5 m 2 in the center of ech plot, nd the yields were clculted with grin moisture content of 0.14 g H 2 Og Greenhouse gs smples Fig. 1 Seedling growth of dry direct-seeded rice (DDSR), wet directseeded rice (WDSR), nd c trnsplnted-flooded rice (TR) during the erly vegettive stge dry direct-seeded rice. In dry direct-seeded rice, the dry seeds were sown on My 3, 2014, nd April 15, The sowing dtes for wet direct-seeded rice were My 5, 2014, nd April 15, For trnsplnted rice, the seeds were sown in nurseries on My 1, 2014, nd April 15, Seedlings tht were 27 nd 31 dys old were trnsplnted into the pddy soil with hill spcing of cm with three seedlings per hill on My 27, 2014, nd My 16, 2015, respectively. The dry direct-seeded rice plots were not irrigted (kept rinfed) until My 21, 2014, nd My 8, 2015, respectively. From then on, 5 10 cm of stnding wter ws kept in the plots until 1 week efore hrvest. The soil in the wet direct-seeded rice plots ws kept sturted efore My 21, 2014, nd My 8, 2015, nd then, 5 10 cm of wter ws mintined until 1 week efore hrvest. The mount of irrigtion wter ws recorded y wter meter tht ws connected to the pump. For ech estlishment method, two cultivrs, Hunghuzhn nd Ynglingyou6, were chosen for the determintion of greenhouse gs emissions. CH 4 nd N 2 O flux were determined using the closed-chmer technique (Pthk et l. 2002) with two different-sized chmers (0.5 m length 0.3 m width 0.65 m height nd 0.5 m length 0.3 m width 1.3 m height). The chmer consisted of crylics nd six flux collrs. All of the chmers were mde from the sme mterils with the sme lengths nd widths. The se of ech chmer ws permnently instlled in the fields during rice growing seson. The top edge of the collr se exhiits groove (5 cm in depth) tht cn e filled with wter to sel the rim of the chmer during gs smpling. An electric fn ws set to ensure complete gs mixing, nd the chmers were covered y sunshde cloth to minimize ir temperture chnges inside the chmer during the smpling. Gs smpling egn 1 dy fter trnsplnting. Gs smple intervls were 14 dys in 2014 nd 7 dys in The gses were smpled from inside the chmers using 100-mL plstic syringes fitted with three-wy stopcocks t 0, 10, nd 20 min fter chmer closure, nd followed y infusion into n empty luminum foil gs collecting g. The smpling time ws etween9:00.m.nd11:00.m.onechsmplingdy. The gs smples were trnsported to the lortory for nlysis y gs chromtogrphy within few hours. The concentrtions of CH 4 nd N 2 O were nlyzed with gs chromtogrph meter (Shimdzu GC-14B; Kyoto, Jpn) equipped with n electron cpture detector for N 2 O nlysis nd flme ioniztion detector for CH 4 nlysis. N 2 (flow rte of

5 24 Pge 4 of 9 Agron. Sustin. Dev. (2016) 36: ml min 1 )ndh 2 (flow rte of 30 ml min 1 )wereuseds the crrier nd fuel gs, respectively. The tempertures of the column, injector, nd detector were set t 55, 100, nd 200 C, respectively. Fluxes were determined from the slope of the mixing rtio chnge in three smples. Glol wrming potentil ws introduced to estimte the potentil future impct of the emissions of different gses on the climte system in reltive sense (Lshof nd Ahuj 1990). CO 2 is generlly tken s the reference gs. Glol wrming potentil (kg CO 2 equivlents h 1 ) ws clculted using the following eqution: Glol wrming potentil (GWP) = CH 4 25+N 2 O 298nd is sed on 100-yer time frme. The totl CH 4 emission, totl N 2 O emission, nd glol wrming potentil were clculted y the verge of two cultivrs. 2.4 Wether dt Meteorologicl dt, except rinfll, were collected from wether sttion (CR800; Cmpell, USA) ner the experimentl field which included dily verge temperture nd solr rdition. Rinfll ws recorded y rin guge locted ner the experiment site. 2.5 Dt nlysis The dt were nlyzed with Sttistix 8.0, nd the men of the tretments were compred with the lest significnt difference test (LSD). Grphicl representtion of the dt ws mde using Sigmplot Results nd discussion 3.1 Grin yield nd yield components The grin yield ws the highest in wet direct-seeded rice, while the grin yields in dry direct-seeded rice were comprle to those in trnsplnted rice (Tle 2). On verge, wet direct-seeded rice produced 7.8 nd 13.7 % more grin yield thn trnsplnted rice in 2014 nd 2015, respectively. The numer of spikelets per squre meter ws highest in wet direct-seeded rice due to the highest pnicle numer per squre meter mong the three estlishment methods (Tle 2). The grin filling percentge nd grin weight in wet direct-seeded rice were close to those in dry directseeded rice nd trnsplnted rice. Thus, the grin yield ws highest in wet direct-seeded rice mong the three estlishment methods. In 2014, the grin yields of YLingyou1 were not significntly different mong the three estlishment methods ecuse of the serious lodging tht occurred in wet direct-seeded rice. In 2014, the hyrid rice vrieties YLingyou1 nd Ynglingyou6 hd higher numer of pnicles per squre meter in dry direct-seeded rice nd more spikelets per pnicle in trnsplnted rice, resulting in no significnt differences in the numer of spikelets per squre meter etween these two crop systems. LvdoQ7 displyed higher grin weight nd grin filling in dry direct-seeded rice, though there were more pnicles nd spikelets per squre meter in trnsplnted rice, which led to similr yields. In 2015, the performnces of grin yield nd yield components under different estlishment methods showed the similr trends to tht in Irrigtion nd wter productivity The mount of precipittion ws greter in 2014 during the rice growing seson thn in 2015 (Tle 1). In trnsplnted rice, wter consumption for puddling, nd irrigtion ccounted for pproximtely 34 nd 55 % of the totl wter input in 2014 nd 2015, respectively (Tle 1). When verged cross the different rice estlishment methods nd cultivrs, the totl wter input (including rinfll nd irrigtion) for dry direct-seeded rice ws reduced y 7.1 nd 4.5 % compred with tht for wet direct-seeded rice nd trnsplnted rice in 2014, respectively, nd reduced y 5.4 nd 11.0 % in 2015, respectively. The irrigtion wter consumption in dry directseeded rice ws reduced y 24.7 nd 13.3 % compred with tht in wet direct-seeded rice nd trnsplnted rice, respectively, when verged cross 2 yers (Tle 1). Numer of irrigtions in dry direct-seeded rice ws lso less thn in wet directseeded rice nd trnsplnted rice (Tle 1). In the present study, wter productivities in the two direct-seeded rice systems were significntly higher thn tht in the trnsplnted rice system (Fig. 2). On verge nd etween the cultivrs, wter productivity in dry direct-seeded rice nd wet directseeded rice ws 7.5 nd 6.2 % higher thn trnsplnted rice in 2014 nd 15.6 nd 20.6 % higher in 2015, respectively. In dry direct-seeded rice, comprle grin yields to trnsplnted rice were chieved with much less wter input. Menwhile, wet direct-seeded rice chieved significntly higher grin yields thn trnsplnted rice with similr mounts of wter consumption, indicting tht wter productivity ws significntly higher in the two direct-seeded rice systems compred with trnsplnted rice. 3.3 CH 4 nd N 2 O emissions nd glol wrming potentil Sesonl totl CH 4 emissions from trnsplnted rice were significntly higher thn from dry direct-seeded rice or wet direct-seeded rice. Compred with dry direct-seeded rice, the mount of CH 4 emission ws higher from wet direct-seeded rice, though the vritions were sttisticlly insignificnt (Fig. 3). On the verge for the two rice vrieties, the sesonl totl CH 4 emissions from dry direct-seeded rice, wet directseeded rice, nd trnsplnted rice were 29.7, 64.6, nd g m 2 in 2014 nd 35.5, 56.8, nd g m 2 in

6 Agron. Sustin. Dev. (2016) 36: 24 Pge 5 of 9 24 Tle 1 Wter input for the four rice cultivrs under dry direct-seeded rice (DDSR), wet direct-seeded rice (WDSR), nd trnsplnted rice (TR) conditions in 2014 nd 2015 Vriety Estlishment methods Irrigtion times Puddling Irrigtion Rinfll Totl wter input Irrigtion times Puddling Irrigtion Rinfll Totl wter input HHZ DDSR WDSR TR LDQ7 DDSR WDSR TR YLY6 DDSR WDSR TR YLY1 DDSR WDSR TR Totl wter input = puddling + irrigtion + rinfll Wter productivity (kg/m 3 ) DDSR WDSR TR HHZ LDQ7 YLY6 YLY1 Fig. 2 Wter productivity for the four rice cultivrs under dry directseeded rice (DDSR), wet direct-seeded rice (WDSR), nd trnsplnted rice (TR) conditions in 2014() nd 2015 (). Hunghuzhn (HHZ), LvdoQ7 (LDQ7), Ynglingyou6 (YLY6),ndYlingyou1(YLY1). The different letters ove the rs indicte tht the difference etween the two rs is significnt t LSD (0.05) 2015, respectively (Fig. 3). The sesonl totl N 2 O emissions were significntly ffected y wter mngement. There were long periods of wterlogging in the three estlishment methods; thus, less N 2 O emissions were detected. However, significntly higher N 2 O emissions were oserved in dry direct-seeded rice thn the other two estlishment methods in 2014, while there were no significnt differences in N 2 O emissions mong the three estlishment methods in 2015 (Fig. 3). Glol wrming potentil ws clculted from sesonl CH 4 nd N 2 O emissions; it ctully depended minly on sesonl CH 4 emissions mong the estlishment methods in the present study. Compred with trnsplnted rice, glol wrming potentil from dry direct-seeded rice or wet directseeded rice ws decresed y 76.9 or 58.5 % in 2014 nd 75.4 or 62.2 % in 2015, respectively (Fig. 3c). In our study, the highest grin yield ws chieved in wet direct-seeded rice, while there were no significnt differences in grin yields etween dry direct-seeded rice nd trnsplnted rice (Tle 2). The highest grin yield of wet direct-seeded rice mong three estlishment methods ws ttriuted to its highest pnicle numer per squre meter resulting from higher tillering ility. Gngwr et l. (2009) nd Rickmn et l. (2001) hve documented tht with proper mngement prctices, wet direct-seeded rice cn otin n even higher grin yield thn trnsplnted rice. However, serious lodging occurred in the hyrid vriety YLingyou1 t the lte grin filling stge (7 dys to hrvest) in wet direct-seeded rice, which resulted in reduced yield gp to trnsplnted rice (Tle 2). This is ecuse high seeding rte for direct-seeded rice is usully dopted s compenstion for poor crop estlishment. The high seeding rte in direct-seeded rice leds to high plnt density, which provides fvorle micro-environment for crop diseses. High plnt density lso rings out smller stem dimeters nd thinner stem wlls. It ws documented tht the distriution of roots in direct-seeded rice ws mostly

7 24 Pge 6 of 9 Agron. Sustin. Dev. (2016) 36: Totl CH4 Emission (g m-2) Totl N2O Emission (g m-2) GWP (g CO 2 equlivent m-2) c in shllow soil lyer compred to trnsplnted rice (Kto nd Okmi 2010). In our study, the mesured lodging index ws significntly higher in wet direct-seeded rice thn in dry direct-seeded rice or trnsplnted rice, ecuse of the significnt higher height of grvittionl center, smller dimeters, nd thinner stem wlls of the third nd fourth internodes from the top in wet direct-seeded rice (dt not shown). All of these differences indicte tht wet direct-seeded rice is more Fig. 3 Totl CH 4 emissions (), N 2 Oemissions(), nd glol wrming potentil (c) under dry direct-seeded rice (DDSR), wet direct-seeded rice (WDSR), nd trnsplnted rice (TR) conditions in 2014 nd Ech dt point is the verge of two rice cultivrs. GWP glol wrming potentil. The different letters ove the rs indicte tht the difference etween the two rs is significnt t LSD (0.05) susceptile to lodging thn the trnsplnted rice during lte grin filling stge. However, rnge of pproches hve een suggested to mitigte the risk of lodging, such s reducing the plnt density y use of pproprite seeding rte, decresing N ppliction t tillering stge, nd controlling diseses nd pests. In ddition, cultivrs with the chrcters of intermedite plnt heights, lrge stem dimeters, thick stem wlls, nd high lignin contents should e red for wet direct-seeded rice to Tle 2 Grin yield nd yield components of the four rice cultivrs under dry direct-seeded rice (DDSR), wet direct-seeded rice (WDSR), nd trnsplnted rice (TR) conditions in 2014 nd 2015 Vriety 2014 HHZ LDQ7 YLY6 YLY HHZ LDQ7 YLY6 YLY1 Estlishment methods Grin yield (t h 1 ) Spikelets (m ) Pnicles (m 2 ) Spikelets per pnicle Grin filling (%) GW (g) DDSR WDSR c TR c DDSR WDSR TR DDSR WDSR TR c DDSR WDSR TR DDSR WDSR TR c DDSR WDSR TR DDSR WDSR TR 9.54 c c DDSR WDSR TR There is column for ech cultivr. The mens re followed y different letters tht represent different significnces t 0.05 proility level ccording to the lest significnt difference (LSD) test

8 Agron. Sustin. Dev. (2016) 36: 24 Pge 7 of 9 24 reduce the lodging susceptiility (Mckill et l. 1996). In dry direct-seeded rice, weeds re one of the min limiting fctors to its wider diffusion mong the frmers. Weeds germinte with rice fter lnd preprtion nd escpe suppression y the wter lyer. High weed infesttion cn cuse 74 % yield losses under the dry direct-seeded rice system (Rmzn 2003). Thus, it is necessry to tke effective nd sustinle weed mngement mesures for dry direct-seeded rice. Due to severe wter shortge in Centrl Chin, dry directseeded rice cn e wter-sving estlishment method. In the present study, the totl wter input for dry direct-seeded rice ws lower thn tht for trnsplnted rice (Tle 1); therefore, the wter productivity ws significntly higher in dry direct-seeded rice thn tht in trnsplnted rice (Fig. 2) due to the comprle grin yield. Consequently, dry directseeded rice is cple of incresing wter productivity while lso reducing lor consumption. Generlly, the mount of wter input in wet direct-seeded rice should e less thn tht of trnsplnted rice. However, irrigtion wter input (including puddling nd irrigtion) in wet direct-seeded rice ws 15 % greter thn tht in trnsplnted rice in 2014 (Tle 1). In our study, the totl wter consumption including rinfll nd irrigtion for direct-seeded rice ws recorded fter direct sowing in the field, while the wter consumption for trnsplnted rice ws recorded only fter seedling trnsplnttion, so the wter input during nursery period ws not recorded for trnsplnted rice. In our study, the wter sving in direct-seeded rice ws not so evident ecuse the plots were kept under flooded conditions soon fter crop estlishment. Some wter mngement prctices could e dopted to further sve the wter input nd increse wter productivity in directseeded rice, such s rinfed (Zho et l. 2007), lternte wet nd dry (Boumn nd Tuong 2001), regulted deficit irrigtion (Chi et l. 2016). Yoshid (1981) reported tht 1240 mm ws n verge wter requirement to produce resonly good crop of rice. Although Boumn et l. (2005)documented tht the totl wter input of rinfed rice in tropicl regions could e reduced to 790 mm, rinfed rice hs shown severe yield penlty. At our experimentl site, the verge rinfll during the growth durtion ws 670 mm (783 mm in 2014 nd 557 mm in 2015), which ws round hlf of the verge wter requirement for good rice growth. Furthermore, wellestlished irrigtion infrstructure nd enough freshwter resources in Centrl Chin ensured dequte irrigtion. Thus, in our present experiments, dry direct-seeded rice ws grown under irrigted-flood conditions during the growth durtion except for erly vegettive stge. It hs een well documented tht the CH 4 nd N 2 O emissions from rice pddies over the pst decdes (Ko et l. 2002; Qin et l. 2010); however, few studies hve focused on the difference etween different direct-seeded rice systems nd trnsplnted rice in CH 4 nd N 2 O fluxes under well-wtered soil conditions. Our study indictes tht sesonl totl CH 4 emission from trnsplnted rice ws significntly higher thn tht from dry direct-seeded rice nd wet direct-seeded rice, which ws consistent with previous studies (Hrd et l. 2007; Ko et l. 2002). In 2014, wter consumption with wet direct-seeded rice is greter thn tht with trnsplnted rice (Tle 1); however, totl CH 4 emission with wet directseeded rice ws significntly lower thn tht with trnsplnted rice (Fig. 3). The opposite trends etween wter consumption nd totl CH 4 emission might e explined y two spects. Firstly, the totl wter consumption with wet direct-seeded rice ws not necessrily greter thn trnsplnted rice, ecuse we did not record the wter input during nursery period for trnsplnted rice. Secondly, the root system of direct-seeded rice differs from tht of trnsplnted rice. It might e possile tht the roots of wet direct-seeded rice were shllower thn tht of trnsplnted rice. With more roots present t the cm depth, there could e more CH 4 oxidized to CO 2,thus reducing the CH 4 emission (Corton et l. 2000; Wtne et l. 1997). In summry, despite the reltively higher N 2 O emissions in dry direct-seeded rice nd wet direct-seeded rice, glol wrming potentil of direct-seeded rice is lower thn tht of trnsplnted rice ecuse of sustntilly low CH 4 emissions in direct-seeded rice. Furthermore, considering the grve threts from glol wrming, more pproprite greenhouse gs emission strtegies must involve ecologiclly intensive food crop mngement prctices tht enhnce resource use efficiency nd mintin high yields (Cssmn 1999). Seeking new type of fertilizer could e one solution. Rose et l. (2014) reported tht the iofertilizer contining plnt growth promoting microorgnisms could replce etween 23 nd 52 % of nitrogen (N) fertilizer without loss of yield. Ali et l. (2014) lso reported tht Anen zolle in comintion with ure nd silicte fertiliztion decresed the totl sesonl CH 4 flux y 12 % nd incresed rice grin yield y 10.6 %. Furthermore, crrier tht consisted of mixture of rice strw nd rice husk sh in 4:1 rtio with Rhodopseudomons plustris could reduce the CH 4 nd CO 2 emissions simultneously (Knth et l. 2015). 4Conclusions Direct-seeded rice is fesile nd sustinle lterntive to trnsplnted rice in Centrl Chin sed on comprle or even higher yield performnces nd greter wter use efficiency. Wet direct-seeded rice is competitive estlishment method in Centrl Chin due to its higher grin yield, wter productivity, nd lower glol wrming potentil thn trnsplnted rice. Dry direct-seeded rice my e suitle for regions where wter levels re low for soil puddling during lnd preprtion, especilly when considering comprle grin yield, less irrigtion, nd lower glol wrming potentil

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