ABSTRACT. Department of Agronomy, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand.

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1 Ksetsrt J. (Nt. Sci.) 49 : (215) Effects of Cultivtion Techniques nd Plot Levels on Growth, Yield nd Yield Components of Lowlnd Rice Grown on Acid Sulfte Soil for Sustinle Production Phyu Thw Tun 1,2, Pitipong Thounluepop 1,*, Ed Srool 1 nd Tnee Sreewongchi 1 ABSTRACT The effects of different cultivtion techniques nd levels on the productivity of lowlnd rice grown on cid sulfte soil were exmined nd field experiment ws conducted in Pthum Thni province, Thilnd. Cultivtion technique (modified cultivtion () technique nd conventionl cultivtion () technique) nd level (upper nd lower ) were the experimentl fctors. Under the technique, the frmer pplied kg.h -1 of compound fertilizer (16-2-) nd kg.h -1 of KCl (--6) t plnting, incorported the previous rice stule nd trnsplnted the rice seedlings, followed y 2 wk flooding nd 1 wk of complete dringe oth throughout the growing period. Under the technique, the frmer pplied kg.h -1 of compound fertilizer (16-2-) t plnting, urned the previous rice stule nd rodcst rice seeds followed y continuous flooding throughout the growing period. The upper ws directly irrigted from dringe cnl wheres the lower ws irrigted with the drined wter from the upper. Compred with the technique, the technique produced significntly higher grin yield, yield components, lef re index, plnt dry weight, net ssimiltion rte nd hrvest index. The upper nd lower s hd no oserved effect on most yield components nd plnt growth prmeters. Overll, the results suggested tht frmers should follow the technique to produce higher rice grin yield long with the improvement of soil properties such s soil ph, ction exchnge cpcity nd orgnic mtter nd to chieve economiclly, environmentlly nd socilly sustinle lowlnd rice production in cid sulfte soil over the long term. Keywords: cid sulfte soil, conventionl cultivtion () technique, modified cultivtion () technique, rice productivity, sustinle rice production INTRODUCTION The enhncement of rice production nd sustinility plys vitl role in grin production to enefit the world s 3 illion people who depend on rice for their livelihood nd s their sic food (Fgeri et l., 23). Previous studies hve reveled tht proper soil nd wter mngement re crucil for sustinle production of crops on cid sulfte soils (Shmshuddin et l., 214). In order to improve resource use efficiency, it will e necessry to ddress the growing concerns regrding higher fertilizer costs, negtive environmentl impcts due to 1 Deprtment of Agronomy, Fculty of Agriculture, Ksetsrt University, Bngkok 19, Thilnd. 2 Deprtment of Agronomy, Yezin Agriculturl University, Yezin, Ny Pyi Tw, Mynmr. * Corresponding uthor, e-mil: pitipongtho@yhoo.com Received dte : 1/7/14 Accepted dte : 17/12/14

2 688 Ksetsrt J. (Nt. Sci.) 49(5) the incresing use of grochemicls for rice production nd wter scrcity (Tsujimoto et l., 29). Hung et l. (213) reveled tht crop residue retention cn significntly increse the rice yield nd prtilly sustitute for inorgnic fertilizers. Residue mngement impcts on the soil orgnic mtter, nd long-term fertility is ecoming more relevnt in the context of soil qulity (DeveÃvre nd Horwth, 2). Chuhn et l. (212) lso proposed tht innovtions in residue mngement to void strw urning should ssist in chieving sustinle productivity nd llow frmers to reduce inputs, mximize yields, increse profitility, conserve the nturl resource se nd reduce risk due to oth environmentl nd economic fctors. The occurrence of sterility is gretly ffected y plnt density (Jvid et l., 212). Compred with trnsplnted rice, rodcsting of direct-seeded rice resulted in less filled grins per pnicle s result of the higher plnt popultion density (Nklng et l., 1996). Flooding the soil hs significnt effect on the ehvior of severl essentil plnt nutrients nd on the growth nd yield of rice. Some nutrients re incresed in vilility to the crop, wheres others re sujected to greter fixtion or loss from the soil s result of flooding (Fgeri et l., 23). High yields cn e etter chieved on well-drined fields. Although high rtes of percoltion cuse nutrient loss, dequte rtes my remove toxic sustnces from the rooting zone nd prevent excessive soil reduction (Yoshid, 1981). Efficient nd environmentlly sound mngement prctices re required for sustinle rice productivity in cid sulfte soil. Agronomic mngement nd technologicl innovtions re needed to led rice productivity nd sustinility in Asin countries (Ali et l., 212). This study ws crried out to compre different cultivtion techniques nd levels on the productivity of lowlnd rice grown on cid sulfte soil for sustinle production. MATERIALS AND METHODS The study ws conducted on rice fields of frmer who hd followed the modified cultivtion () technique for 15 yr nd lso on those of frmer who hd followed the conventionl cultivtion () technique continuously. The fields were locted in Pthum Thni province (ltitude, 14.2 N nd longitude 1.53 E), Thilnd. This study ws crried out with eight oservtions for ech level of two fctors. The re of ech oservtion ws 1 m 2 nd 1 plnts were smpled from ech oservtion re to collect the dt. The experimentl field lyout is shown in Figure 1. The durtion of the field experiment ws from Septemer 212 to Ferury 213. Fctor A ws cultivtion technique, consisting of either the modified cultivtion () technique or the conventionl cultivtion () technique. Under the technique, the frmer pplied kg.h -1 of compound fertilizer (16-2-; 3 kg.h -1 N nd 37.5 kg.h -1 P s P 2 O 5 ) nd kg.h -1 of KCl (--6; kg.h -1 K s K 2 O) t plnting, incorported the stule of the previous rice crop into the soil 1 mth efore plnting the successive rice crop, trnsplnted 2-dy-old seedlings t five per hill using trnsplnting mchine, nd 2 wk irrigtion nd 1 wk of complete dringe oth throughout the growing period. Under the technique, the frmer pplied kg.h -1 of compound fertilizer (16-2-; 5 kg.h -1 N nd 62.5 kg.h -1 P s P 2 O 5 ) t plnting, urned the stule of the previous rice crop, followed y mnul rodcsting method using pre-germinted seeds nd continuous flooding of the field throughout the growing period. Fctor B ws the level, consisting of either the upper which ws directly irrigted from dringe cnl or the lower which ws irrigted with the drined wter from the upper. In the technique, the upper ws 45 cm higher thn the middle which ws

3 Ksetsrt J. (Nt. Sci.) 49(5) cm higher thn lower. The upper ws directly irrigted from dringe cnl nd then drined to the lower through the middle. In the technique, the upper ws 45 cm higher thn the frm rod which ws 45 cm higher thn the lower. The upper ws directly irrigted from dringe cnl nd then drined to the lower vi the frm rod. The prctices of different cultivtion techniques nd levels re shown in Tle 1. Eight soil smples of 1 kg ech were rndomly collected from ech experimentl efore plnting nd fter hrvesting nd nlyzed using generl soil nlysis methods to evlute soil ph, electricl conductivity (EC; mesured in ds.m -1 ), ction exchnge cpcity (CEC; mq) nd orgnic mtter content. The dt collected were plnt height (cm), numer of leves per plnt, lef re index (LAI), plnt fresh weight (g), plnt dry weight (g), net ssimiltion rte (g.m -2.d -1 ), pnicle length (cm), numer of spikelets per pnicle, filled grin percentge (%), 1, grins weight (g), hrvest index (HI) nd grin yield (t.h -1 ). The growth prmeters were collected from 1 smple plnts from ech oservtion re, which were rndomly selected, t two-weekly intervls during the vegettive period. Anlysis of vrince ws done sed on completely rndomized design using the SPSS sttisticl pckge (version 16.; SPSS Inc. Chicgo, IL, USA) to test for the existence of sttisticl differences in growth prmeters, yield components nd the yield etween the two techniques s well s etween the two levels. Cultivtion technique, with two levels ( technique nd technique), ws used s fctor A. Plot level, with two levels (upper nd lower ), ws used s fctor B. Eight oservtions were used s replictes. Figure 1 Experimentl field lyout.

4 69 Ksetsrt J. (Nt. Sci.) 49(5) RESULTS AND DISCUSSION Soil chemicl properties efore plnting nd fter hrvesting under different cultivtion techniques nd levels Soil nlysis efore plnting nd fter hrvesting showed tht higher soil ph, CEC, nd orgnic mtter were otined from the technique compred with the technique. The soil EC ws higher under the technique thn tht under the technique. Higher soil ph nd EC vlues were oserved in the upper nd Tle 1 Prctices of different cultivtion techniques nd levels. Modified cultivtion technique Conventionl cultivtion technique Prctice Lower Upper Lower Upper Frm field re (h) 1.6 ( m 9.92 m) Time for lnd preprtion 2 Sep 212 to 25 Oct ( m 9.92 m) 2 Sep 212 to 25 Oct (155.7 m 82.21m) 2 Sep 212 to 25 Oct (155.7 m m) 3Sep 212 to 5 Oct 212 Time of plnting 1 Oct Oct Oct Oct 212 Seeding rte (kg.h -1 ) Nme of cultivr RD 47 RD 47 RD 47 RD 47 Sowing method Trnsplnting using mchine Trnsplnting using mchine Direct seeding (mnully) Direct seeding (mnully) Plnt spcing (cm cm) Age of seedlings (d) Numer of seedlings per hill 5 5 Brodcsting Brodcsting Bsl fertilizer (kg.h -1 ) (187.5) --6 (18.75) Residue mngement Incorporting stule (187.5) --6 (18.75) Incorporting stule (312.5) Burning stule (312.5) Burning stule Alternte irrigtion nd dringe Wter mngement Irrigtion (dys fter trnsplnting) Dringe (dys fter trnsplnting) Continuous flooding Time of hrvesting 5 Jn Jn Fe Fe 213

5 Ksetsrt J. (Nt. Sci.) 49(5) 691 lrger mount of orgnic mtter ws recorded in the lower. The CEC ws not ffected y the level (Tles 2 nd 3). Plnt height The technique produced significntly tller plnts thn the technique t 21 nd 49 d fter plnting (Figure 2). In ech growing period, the lower produced tller plnts compred with the upper (Figure 3). The tller plnts from the technique were proly due to the competition for incident solr rdition mong the djcent plnts resulting from the closer spcing in the rodcsting method. This ssumption is supported y Hsnuzzmn et l. (29) who oserved tht plnts tended to e tller if Tle 2 Soil chemicl properties efore plnting under the modified cultivtion technique () nd the conventionl cultivtion technique () nd the upper nd the lower. Cultivtion fctor Soil ph Soil electricl conductivity (ds.m -1 ) Soil ction exchnge cpcity (mq) Soil orgnic mtter (%) Rice cultivtion technique (Fctor A) technique technique F test ** ** ** ** Plot level (Fctor B) Upper Lower F test ** ** ns ** Coefficient of vrition (%) Vlues in column followed y different letters re significntly different. ** = Significntly different t P.1, * = Significntly different t P.5, ns = Not significntly different. Tle 3 Soil chemicl properties fter hrvesting under the modified cultivtion technique () nd the conventionl cultivtion technique () nd the upper nd the lower. Cultivtion fctor Soil ph Soil electricl conductivity (ds.m -1 ) Soil ction exchnge cpcity (mq) Soil orgnic mtter (%) Rice cultivtion technique (Fctor A) technique technique F test ** ** ** ** Plot level (Fctor B) Upper Lower F test ** ** ns ** Coefficient of vrition (%) Vlues in column followed y different letters re significntly different. ** = Significntly different t P.1, * = Significntly different t P.5, ns = Not significntly different.

6 692 Ksetsrt J. (Nt. Sci.) 49(5) they received light in closed plce. The tller plnts in the lower were perhps lso due to greter nutrient uptke, especilly nitrogen, from the leched nutrient in the dringe wter from the upper resulting in incresed vegettive growth. Awn et l. (211) stted tht the increse in plnt height with incresed nitrogen ppliction might e primrily due to enhnced vegettive growth resulting from greter nitrogen supply to the plnt. Plnt height (cm) Dys fter plnting Figure 2 Men plnt height of rice under the modified cultivtion () technique nd the conventionl cultivtion () technique. Brs in ech pir of plnt heights with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Numer of leves per plnt Lef production under the two cultivtion techniques ws not significntly different until 35 d fter plnting. After this period, the produced significntly higher lef numer; however, it ws not numericlly different (Figure 4). The results illustrted in Figure 5 show there ws no significnt difference in the numer of leves produced in the two levels t 21 d fter plnting. Although there ws no numericl Numer of leves per plnt Dys fter plnting Figure 4 Men numer of leves per plnt of rice under the modified cultivtion () technique nd the conventionl cultivtion () technique. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Plnt height (cm) Dys fter plnting Upper Lower Figure 3 Men plnt height of rice in the upper nd lower. Brs in ech pir of plnt heights with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Numer of leves per plnt Dys fter plnting Figure 5 Men numer of leves per plnt of rice in the upper nd lower. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Upper Lower

7 Ksetsrt J. (Nt. Sci.) 49(5) 693 difference in the numer of leves, plnts in the lower produced sttisticlly higher numer of leves t 35 d fter plnting nd the production of leves in tht sttisticlly decresed t 49 d fter plnting, wheres the lef production in the upper constntly incresed. Lef re index The results showed tht the technique produced significntly higher LAI compred with the technique until 35 d fter plnting. However, t 49 d fter plnting, there ws no significnt difference in the LAI etween the nd techniques. (Figure 6). A significnt difference etween the upper nd lower s ws found only t 35 d fter plnting, where the lower produced greter LAI thn the upper (Figure 7). As the LAI is the rtio of totl functionl lef re to ground re where the leves hve een collected, the higher numer of leves under the technique might support lrger functionl lef re per unit lnd re resulting in n increse in the LAI. The smller LAI in the technique ws possily the result of the smller functionl lef re per unit lnd re resulting from the lower numer of leves. Lef re index (LAI) Dys fter plnting Figure 6 Men lef re index of rice under the modified cultivtion () technique nd the conventionl cultivtion () technique. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Plnt fresh weight The results indicted significnt increse in the plnt fresh weight under the technique compred to the technique throughout the growing period (Figure 8). At 21 nd 35 d fter plnting, the plnt fresh weight in the lower ws significntly higher thn tht in the upper. However, there ws no significnt difference in the plnt fresh weight etween the two techniques t 49 d fter plnting (Figure 9). Lef re index (LAI) Figure 7 Men lef re index of rice in the upper nd lower. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Plnt fresh weight (g) Dys fter plnting Figure 8 Men plnt fresh weight of rice under the modified cultivtion () technique nd the conventionl cultivtion () technique. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Dys fter plnting Upper Lower

8 694 Ksetsrt J. (Nt. Sci.) 49(5) The ppliction of potssium (K) fertilizer nd the incorportion of K-undnt rice stule in the technique might support thicker stem with higher moisture content resulting in higher shoot fresh weight. The culm s mechnicl strength is incresed y K pplictions, which increse its thickness (Noguchi, 194) nd mintins high turgor pressure in the cells (Kono nd Tkhshi, 1961). The incresed plnt fresh weight in the lower in the erly growing period could e ttriuted to the vilility of more nutrients in the drined wter from the upper resulting in etter plnt growth nd therey incresing the plnt fresh weight. Plnt dry weight The technique produced higher plnt dry weight until 35 nd 49 d fter plnting (Figure 1). Plnts in the lower ccumulted higher dry mtter t 21 nd 35 d fter plnting. However, t 49 d fter plnting, there ws no significnt difference in dry mtter production etween the levels (Figure 11). The increse in plnt dry mtter of the technique could e ttriuted to the increse in the LAI of tht technique. The increses in plnt dry mtter in the lower t 21 nd 35 d fter plnting were proly due to the increse in the LAI. This is supported y Shieh (1977) who reported Plnt fresh weight (g) Figure 9 Men plnt fresh weight of rice in the upper nd lower. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Dys fter plnting Upper Lower significnt, positive correltion coefficient etween the LAI nd the crop growth rte in the vegettive growth stge. Net ssimiltion rte The dt shown in Figure 12 revel tht the technique hd higher NAR thn the technique t oth 35 nd 49 d fter plnting. No significnt difference in the NAR ws found Plnt dry weight (g) Figure 1 Men plnt dry weight of rice under the modified cultivtion () technique nd the conventionl cultivtion () technique. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Plnt dry weight (g) Dys fter plnting Figure 11 Men plnt dry weight of rice in the upper nd lower. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Dys fter plnting Upper Lower

9 Ksetsrt J. (Nt. Sci.) 49(5) 695 etween levels (Figure 13). The increses in the LAI nd plnt dry mtter under the technique were possily due to the increse in the NAR under the technique. Closer spcing in the rodcsting method of the technique resulted in mutul shding mong leves in the cnopy, leding to lower incidence of solr rdition for photosynthesis which might result in decresed NAR. Net ssimiltion rte (g m-2 dy-1) Figure 12 Men net ssimiltion rte of rice under the modified cultivtion () technique nd the conventionl cultivtion () technique. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Net ssimiltion rte (g m-2 dy-1) Figure 13 Men net ssimiltion rte of rice in the upper nd lower. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE Dy fter plnting Dys fter plnting Upper lower Grin yield Compred with the technique, significntly higher grin yield ws recorded under the technique (Figure 14). The upper nd lower s produced similr grin yields (Figure 15). Production of higher LAI resulting in greter dry mtter production nd higher NAR might hve een the reson for the higher grin yield. Thkur nd Ptel (1998) reported tht the LAI, dry mtter production nd the NAR Grin yield (t.h -1 ) Rice cultivtion technique Figure 14 Men grin yield of rice under the modified cultivtion () technique nd the conventionl cultivtion () technique. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Grin yield (t.h -1 ) Upper Lower Plot level Figure 15 Men grin yield of rice in the upper nd lower. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE.

10 696 Ksetsrt J. (Nt. Sci.) 49(5) re ultimtely reflected in higher grin yield. The higher grin yield recorded under the technique might hve een due to the production of significntly higher numer of filled grins resulting in lrger HI (Ye et l., 213). The higher grin yield under the technique might hve lso een due to efficient nutrient utiliztion s the result of incresed orgnic mtter y stule incorportion. Tnk (1978) stted tht orgnic mtter supplies nitrogen (N) to rice plnts throughout the growing period nd this continuous N supply fvors high yield y preventing excessive vegettive growth nd lodging. The incorportion of cerel strw long with inorgnic fertilizer ppliction resulted in high rte of N minerliztion nd susequent high rice grin yield (Singh nd Singh, 1995). Hung et l. (213) lso found tht the rice yield ws not dversely ffected y crop residue retention with reduced rtes of inorgnic N, phosphorus (P) nd K fertilizers compred with full rtes of inorgnic fertiliztion lone. Crop residue retention cn significntly increse the rice yield nd sustitute for some inorgnic fertilizer (Hung et l., 213). Yng nd Zhng (26) nd Xue et l. (213) lso stted tht midseson dringe nd lternte wetting nd drying cn inhiit the formtion of unproductive tillers, improve root ctivity nd enhnce grin filling, thus incresing the rice yield. Lodging under the technique possily inhiited the trnsloction of ssimiltes for grin filling resulting in higher percentge of unfilled grin nd susequent lower grin yield. Pnicle length There ws longer pnicle length under the technique thn in the technique. This prmeter ws not significntly ffected y level (Tle 4). Numer of spikelets per pnicle The differences in the numer of spikelets per pnicle etween the two cultivtion techniques were not significnt. Similrly, the numer of spikelets per pnicle ws not significntly ffected y level (Tle 4). Tle 4 Different cultivtion techniques nd different levels on yield components of lowlnd rice. Pnicle length (cm) Numer of spikelets per pnicle Filled grin percentge (%) 1, grins weight (g) Rice cultivtion technique (Fctor A) technique technique F test * ns ** ns Coefficient of vrition (%) Plot level (Fctor B) Upper Lower F test ns ns ns * Coefficient of vrition (%) Vlues in column followed y the different letters re significntly different. ** = Significntly different t P.1, * = Significntly different t P.5, ns = Not significntly different

11 Ksetsrt J. (Nt. Sci.) 49(5) 697 Filled grin percent A higher filled grin percentge ws recorded under the technique compred to the technique wheres grin filling ws not ffected y level (Tle 4). Xu et l. (21) reported tht residue retention could ccelerte grin filling, which my e scried to etter nutrient supply in the lte rice-growing period. Closer spcing resulted in tller plnts under the technique which might hve een more susceptile to lodging (Yoshid, 1981). Premture lodging my hve decresed the trnsloction efficiency nd grin filling nd incresed sterility (Murt nd Mtsushim, 1975) s well s reducing the grin yield (Sn-oh et l., 21). Potssium is known to ply n importnt role in the lignifiction of vsculr undles tht contriutes to the higher susceptiility to lodging of K-deficient plnts (Fgeri et l., 23). The lck of K fertilizer nd the stule urning under the technique might hve cused decresed K vilility nd susequently incresed the susceptiility to lodging. Thousnd grin weight The results indicted tht 1, grin weight ws not significntly different etween the two cultivtion techniques, wheres the upper produced lrger grins compred to the lower (Tle 4). Hrvest index A significntly higher HI ws recorded under the technique compred to the technique (Figure 16). The hrvest index ws not significntly different etween the upper nd lower (Figure 17). The greter HI under the technique ws proly due to the higher filled grin percentge of tht technique nd the higher percentge of empty grin might hve contriuted to the lower HI under the technique. Ye et l. (213) lso recorded tht the production of significntly higher numer of filled grin results in lrger HI. CONCLUSION Compred with the technique, the technique produced significntly higher grin yield nd yield components such s the filled grin percentge, LAI, plnt dry weight, NAR nd HI. The effects of the upper nd lower on yield nd most yield Hrvest index Rice cultivtion technique Figure 16 Men hrvest index of rice under the modified cultivtion () technique nd the conventionl cultivtion () technique. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE. Hrvest index Upper Lower level Figure 17 Men hrvest index of rice in the upper nd lower. Brs in ech pir of results with the sme lower cse letter re not significntly different t P <.5; error rs indicte ± SE.

12 698 Ksetsrt J. (Nt. Sci.) 49(5) components nd plnt growth prmeters were not sttisticlly different. The modified cultivtion technique might led to economic sustinility through reducing fertilizer nd seed costs nd incresing the profit from higher rice grin yield; to environmentl sustinility through reducing the use of grochemicl fertilizers nd environmentl pollution y stule urning; nd to socil sustinility y voiding the risks from grochemicls nd dust from stule urning. Overll, the results suggested tht frmers should follow the technique to chieve higher productivity of lowlnd rice with improvements to soil properties such s soil ph, CEC nd orgnic mtter nd to chieve economiclly, environmentlly nd socilly sustinle lowlnd rice production in cid sulfte soil over the long term. ACKNOWLEDGEMENTS The uthors grtefully cknowledge the Thilnd Interntionl Development Coopertion Agency (TICA) for finncil support of this study. LITERATURE CITED Ali, R.I., N. Iql, M.U. Sleem nd M. Akhtr Effect of different plnting methods on economic yield nd grin qulity of rice. Int. J. Agric. Appl. Sci. 4: Awn, T.H., R.I. Ali, Z. Mnzoor, M. Ahmd nd M. Akhtr Effect of different nitrogen levels nd row spcing on the performnce of newly evolved medium grin rice vriety, ksk J. Anim. Plnt Sci. 21: Chuhn, B.S., G. Mhjn, V. Srdn, J. Timsin nd M.L. Jt Productivity nd sustinility of the rice-whet cropping system in the Indo-Gngetic Plins of the Indin sucontinent: Prolems, opportunities, nd strtegies. Adv. Agron. 117: DeveÃvre, O.C. nd R.W. Horwth. 2. Decomposition of rice strw nd microil cron use efficiency under different soil tempertures nd moistures. Soil Biol. Biochem. 32: Fgeri, N.K., N.A. Slton nd V.C. Bligr. 23. Nutrient mngement for improving lowlnd rice productivity nd sustinility. Adv. Agron. 8: Hsnuzzmn, M., M.L. Rhmn, T.S. Roy, J.U. Ahmed nd A.S.M. Zoer. 29. Plnt chrcters, yield components nd yield of lte trnsplnted Amn Rice s ffected y plnt spcing nd numer of seedling per hill. Adv. Biol. Res. 3: Hung, S., Y. Zeng, J. Wu, Q. Shi nd X. Pn Effect of crop residue retention on rice yield in Chin: A met-nlysis. Field Crop Res. 154: Jvid, T., I.U. Awn, M.S. Bloch, I.H. Shh, M.A. Ndim, E.A. Khn, A.A. Khkwni nd M.R. Auzr Effect of plnting methods on the growth nd yield of corse rice. J. Anim. Plnt Sci. 22: Kono, M. nd J. Tkhshi Studies on the reltionship etween reking strength nd osmotic pressure of pddy stem. J. Sci. Soil Mnure. Jpn. 32: Murt, Y. nd S. Mtsushim Rice, pp In L.T. Evns (ed.), Crop Physiology. Cmridge University Press. Cmridge, UK. Nklng, K., S. Fuki nd K. Nthut Growth of rice cultivrs y direct seeding nd trnsplnting under uplnd nd lowlnd conditions. Field Crop Res. 48: Noguchi, Y Influence of potssium nutrition on culm structure of the rice plnt. Proc. Crop Sci. SOC. Jpn. 11: Cited S. Yoshid Fundmentls of Rice Crop Science. The Interntionl Rice Reserch Institute. Los Bños, the Philippines. Sn-oh, Y., T. Ookw, N. Aizw nd T. Hirsw. 21. Vrietl differences in growth, lodging nd relted chrcters of rice

13 Ksetsrt J. (Nt. Sci.) 49(5) 699 plnts rodcsted in sumerged pddy field t different densities. Jpn. J. Crop Sci. 7: Shmshuddin, J., A.A. Elis, M.A.R.S. Shzn, C.I. Fuzih, Q.A. Pnhwr nd U.A. Nher Properties nd mngement of cid sulfte soils in southest si for sustinle cultivtion of rice, oil plm, nd coco. Adv. Agron. 124: Shieh Yhu-Jng Effect of plnting density on community photosynthesis nd yielding components of rice plnts. Bot. Bull. Acd. Sinic. 18: Singh H. nd K.P. Singh Effect of plnt residue nd fertilizer on grin yield of drylnd rice under reduced tillge cultivtion. Soil Till. Res. 34: Thkur D.S. nd S.R. Ptel Growth nd sink potentil of rice s influenced y the split ppliction of potssium with FYM in inceptisols of estern centrl Indi. J. Potssium Res. 14: Tnk, A Role of orgnic mtter, pp In Soils nd Rice. Interntionl Rice Reserch Institute. Los Bños, the Philippines. Tsujimoto, Y., T. Horie, H. Rndrimihry, T. Shiriw nd K. Homm. 29. Soil mngement: The key fctors for higher productivity in the fields utilizing the system of rice intensifiction (SRI) in the centrl highlnd of Mdgscr. Agr. Syst. 1: Xu, Y, L. Nie, R.J. Buresh, J. Hung, K. Cui, B. Xu, W. Gong nd S. Peng. 21. Agronomic performnce of lte-seson rice under different tillge, strw, nd nitrogen mngement. Field Crop Res. 115: Xue, Y., H. Dun, L. Liu, Z. Wng, J. Yng nd J. Zhng An improved crop mngement increses grin yield nd nitrogen nd wter use efficiency in rice. Crop Sci. 53: Yng, J. nd J. Zhng. 26. Grin filling of cerels under soil drying. New Phytol. 16: Ye, Y., X. Ling, Y. Chen, J. Liu, J. Gu, R. Guo nd L. Li Alternte wetting nd drying irrigtion nd controlled-relese nitrogen fertilizer in lte-seson rice. Effects on dry mtter ccumultion, yield, wter nd nitrogen use. Field Crop Res. 144: Yoshid, S Fundmentls of Rice Crop Science. The Interntionl Rice Reserch Institute. Los Bños, the Philippines. 269 pp.