Broadcast-seeded Rice Research Articles

Impact of Hydrogel Polymer on Water Productivity, Weed Control Efficiency and Yield of Broadcast-Seeded Rice

A field study was investigated at the Experimental Farm of Rice Research Department, Sakha Agricultural Research Station, Kafrelsheikh, Egypt during summer seasons of 2020 and 2021 to study the capability of hydrogel polymer application under different irrigation intervals and chemical weed control on water conservation and weed control under Egyptian broadcast-seeded rice (Giza 179 cv). A strip spit design with three replicates was used during the study. Three irrigation intervals (irrigation every 5 days (I1), 10 days (I2) and every 15 days (I3) were randomly devoted in horizontal plots, hydrogel polymer at rate of 20 kg ha-1 as compared to normal soil (zero hydrogel) were assigned in vertical plots, while three weed control treatments (thiobencarb at 2.38 kg ai ha-1 at 9 days after sowing (DAS) followed by (fb) bispyribac-sodium at 0.038 kg ai ha-1 + halosulfuron-methyl at 0.036 Kg ha-1 applied at 25 DAS (W1), Thiobencarb at 2.38 kg ai ha-1 fb cyhalofop-butyl at 0.286 Kg ai ha-1 + halosulfuron-methyl at 0.036 Kg ha-1 applied at 25 DAS (W2) as compared to un-treated weedy check plots (W3) were allocated in endo/sub-sub plots. Results showed that irrigation every 10 and 15 days saved about 26.4% and 35.8% of applied water, respectively, while the yield reduced by 31.8% and 56.1% respectively compared to irrigation every 5-days as average of the two seasons. The lowest dry weights of grasses and total weeds were recorded of I1, while C. difformis weed was absent under I3 during 2020 and 2021 seasons. Hydrogel polymer application conserved about 14.8% of applied water and improved rice grain yield by 16.5% as well as increased water productivity to be 0.48 kg m-3 compared to 0.32 kg m-3 for without hydrogel treatment. Hydrogel encouraged C. difformis appearance while decreased grasses and total weeds compared to without hydrogel. Sequential herbicides application W1 recorded the best weed control against grasses, C. difformis and total weeds in addition to higher WCE (91.9%) against total weeds consequently produced the highest values of rice dry matter, yield and its attributes during both seasons of study. The interaction of I1 x hydrogel x W1 achieved the highest grain yield (10.11 t ha-1) with same significance for I1 x without hydrogel x W1 (9.75 t ha-1), while I2 x hydrogel x W1 recorded the highest water productivity (0.78 kg m-3) and produced 7.63 t ha-1 of rice grain yield by increasing of 20.7% than I2 x without hydrogel x W1 as average for 2020 and 2021 seasons.

Effect of Zinc Foliar Application Splits and Rates Integrated with Humic Acid on Growth, Yield, and Grain Quality of Broadcast-Seeded Rice (Oryza sativa L.) in Northern Nile Delta Region, Egypt

Effect of Zinc Foliar Application Splits and Rates Integrated with Humic Acid on Growth, Yield, and Grain Quality of Broadcast-Seeded Rice (Oryza sativa L.) in Northern Nile Delta Region, Egypt

Field Evaluation and Molecular Detection of Allelopathic Potential for Some Rice Genotypes to Improve Weed Management and Grain Yield of Broadcast-Seeded Rice

A field study was carried out at the Experimental Farm of Rice Research Dept., Sakha Agricultural Research Station, ARC, Egypt through 2016 and 2017 seasons to study allelopathic activity of selected rice genotypes to integrate with herbicides use under field conditions and to assess genetic diversity using SSR markers linked to allelopathic activity. Six rice entries were used in field study included MBG-41, HHZ-12-SAL8-Y1-Y2, FFZ-1, Weed tolerant-1, Sakha 106 and non-allelopathic check Sakha 101. Pre-mixed herbicide Top Shot 6% OD (penoxsulam 1% + cyhalofop-butyl 5%) was applied at recommended and half doses as compared with un-treated (weedy check) plots. Sakha 106 and Weed tolerant-1 performed the best in weed control, yield and yield attributes in both seasons, while Sakha 101 recorded the highest dry weights of studied weeds and lowest values of rice dry weight as well as grain yield and its attributes during both seasons. The recommended dose of Top Shot 6% OD was the best as compared to either half dose or un-treated plots. Sakha 106 as allelopathic rice cultivar had same behavior under both recommended and half doses of herbicide in controlling grasses, sedges, broad leaves and total weeds, and produced the highest rice dry weight, grain yield and its attributes in both seasons. For molecular study, Rikuto Norin22 was used as identified allelopathic genotype. Four previously identified SSR markers linked to allelopathic activity in rice were used to study genetic diversity among studied rice genotypes. A total number of 13 alleles were generated and number of alleles per locus varied from 2 to 5. Heterozygosity (He)values ranged from 0.490 to 0.735 with an average of 0.607. Polymorphic Information content (PIC) values ranged from 0.37 to 0.685. Genotypes were clustered based on genetic background and allelopathic activity. The results demonstrated the power of SSR markers in detecting molecular diversity as they separated indica from japonica genotypes. SSR 227 was able to detect Weed tolerant-1 and Rikuto Norin22 and Sakha106. This marker could be a potential candidate for MAS-based allelopathic selection.

Effect of Rice Cultivars and Herbicidal Combinations Integrations on Weeds and Yield of Broadcast-Seeded Rice Productivity and Economic Feasibility

Nowadays there was an attitude from farmers to grow broadcasted seeded rice as an alternative to transplanted rice due to the scarce and costly labors in rice transplanting, but broadcasted seeded rice suffer severely from weed competition where sometimes the yield was sometimes completely lost. Finding good weed control package in rice fields which consist from. Main findings show that the use of old and newly herbicide molecules combination can succeed for sowing and rice broadcasted rice without problem. For these reasons two field experiments were conducted in split plot design were carried out at the Farm of Sakha Agricultural Research Station, Sakha, Kafrelshiekh , Governorate, Egypt during 2016 and 2017 summer seasons to evaluate the effect of two rice cultivars allocated as in the main plots two broadcasted seeded rice cultivars Sakha 106 and Sakha 104 were used in this study and thirteen weed control treatments which were the use of single herbicides or their combinations assigned in sub plots namely; Nominee at the rate of 800 cm/faddan, Saturn at the rate of 2 L faddan, Sirius at the rate of 80g/faddan, Basagran at the rate of 1.5 L/ faddan, Inpul at the rate of 20g/ faddan, Nominee at the rate of 800 cm L/faddan, followed by Basagran at the rate of 1.5 L/faddan, Nominee at the rate of 800cm /faddan followed by Sirius at the rate of 80g/faddan, Nominee at the rate of 800 cm/faddan followed by Inpul at the rate of 20g/ fed, Saturn at the rate of 2 L/faddan followed by Sirius at the rate of 80gfaddan, Saturn at the rate of 2 L/faddan followed by Basagran at the rate of 1.5 L/ faddan, Saturn at the rate of 2 L/faddan , followed by Inpul at the rate of 20g/faddan, hand weeding twice at 30 and 45 days and untreated check in each experiment on weeds, rice grain yield and its components as well as economic evaluation. Main finding results show that Sakha 106 cultivar had competiveness ability to weeds by good growth canopy and can participate by 24.9 & 25.0% weed suppression and increasing rice grain yield as tonnage per faddan by 10.55 & 15.09 % as compared with Sakha104 cultivar in both 2016 and 2017 seasons, respectively. This may be due that the vigorous growth of Sakha 106 cultivar which attributed to that cultivar more taller, more tillers and higher growth parameters to cover soil surface namely CGR,RGR and NAR which shed weeds and can combate with weeds than cultivar Sakha 104 conditions. On the other side the all used single herbicides or their combination succeeded to control weeds in rice yield by 37, 41 % and increasing grain yield as to tonnage per faddan by 1.398, 1.475 and exceeded hand weeding twice in two seasons, respectively. This may be due to the early elimination of weed competition and consequently improving rice all above rice growth parameters to utilize of natural resources of nutrients, light and space than untreated plots which heavily infested by weeds. The integration between both the role of rice cultivars and herbicides can maximize weed control and increase grain yield as tonnage per faddan than the use of single factor accompanied high incomes farmers. Application of inpul 20g /faddan+ Nominee 800 cm/faddan economical is considered as a good alternative to traditional weed control in broadcasted rice gave 82.9&84.% controlling of total weeds and increase in rice grain yield by 61.6 & 71.0% and exceeded hand weeding twice treatments as normal farmer practice for weed control in rice which gave 77.4 &77.7% weed control and increased grain yield 43.97 59.1 % in first and second seasons, respectively. Economic feasibility study of various studies weed management packages results referred clearly that under Kafrelshiekh condition by planting Sakha 106 cultivar with the use of any one of studied herbicides weed management is packages in broadcasted seeded rice and the best.

Effect of Preceding Winter Crops and Herbicidal Combinations on Weeds, Yield and Econemic Feasability of Broadcast-Seeded Rice Productivity.

Nowadays, in Egypt there is a big shift towards increasing the cultivated area with broadcast-seeded rice which needs to overcome the heavy out weeds infestation in this case. Thus, four field experiments were conducted at the Experimental Farm of El-Serw Agri. Res. Station, Damietta Governorate in 2014 and 2015 summer seasons, to investigate effect of clover and wheat as two preceding winter crops before sowing the rice as broadcast-seeded rice and six weed control treatments [Saturn at 2.0 L/ faddan + Basagran at 1.5 L/ faddan, Ronstar at 0.75 L/ faddan + Enpul at 20 g/faddan, Rainbow at 0.4 L/ faddan + Enpul at 20 g/ faddan, Rainbow at 0.4 L/ faddan + Basagran at 1.5 L/ faddan combinations, hand weeding twice and untreated check] in each experiment on weeds, rice grain yield and its components with economic evaluation. The main findings indicated that sowing the rice as broadcasted after clover; and weed control treatments irrespective of the preceding winter crops decreased significantly the dry weight of both dicot and monocot weeds and markedly increased rice grain yield (ton/faddan) and its components i.e., plant height, number of tillers/m2, number of panicles/m2, number of filled grain/panicle and weight of grain/panicle, that is true in both seasons. In first season the interaction between clover as a preceding winter crop and herbicides combinations i.e. Rainbow 2.5% OD (penoxsulam) at 0.4 L/ faddan followed by Enpul 75% WG (halosulfuron-methyl) at 20 g/faddan; Rainbow 2.5% OD at 0.4 L/faddan followed by Basagran 48% AS (bentazon) at 1.5 L/ faddan; Ronstar 25% EC (oxadiazon) followed by Enpul 75% WG at 20 g/faddan and Saturn 50% EC (thiobencarb) at 2.0 L/faddan followed by Basagran 48% AS at 1.5 L/faddan reduced the total weeds by 91.7, 91.3, 88.5 and 86.3%, respectively, at 70 DAS, and accompanied with significant increases on rice grain yield by 145.3, 154.0, 122.0 and 148.0% than untreated check, respectively. Whilst, hand weeding twice was less effective on reducing the total weeds by 56.5 and 53.4% at the respective assessments and reflect that to increase rice grain yield in both seasons. The highest net income/faddan were obtained by the previous herbicidal combinations in trials preceded with clover than wheat during the two seasons. This study throw lights about suitable and satisfactory herbicidal combinations to overcome the heavy weeds infestation problem in broadcast-seeded rice. These results indicated that under heavy infestation with weeds in broadcast- seeded rice, it is possible to grow broadcast-seeded rice after clover with using one herbicides combinations,( Rainbow at 0.4L/fed + Enpul at 20 g/fed, Rainbow at 0.4L/fed + Basagran at 1.5 L/fed, Ronstar at 0.75 L/fed + Enpul at 20g/fed; and Saturn at 2.0 L/fed + Basagran at 1.5 L/fed) which, gave the highest redution weeds, increase broadcast- seeded rice yield and the highest economic values in both seasons.

EFFECT OF SPLIT APPLICATION OF NITROGEN FERTILIZER ON MORPHO-PHYSIOLOGICAL ATTRIBUTES AND GRAIN YIELD OF BROADCAST SEEDED EGYPTIAN HYBRID RICE (Ι)

An experiment was carried out at the Experimental Farm of Rice Research and Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt, during 2011 and 2012 seasons. The experiment was laid out in a split plot design with four replications. The main plots were devoted to the nitrogen level 220kg N/ha in form of urea (46.5% N). The sub-plots were allocated to the six times of nitrogen application to assess the effect of six nitrogen application treatments, viz., T_1: (2⁄(3 ) as B ( basal ) + 1⁄3 at PI ( panicle initiation)), T_2: (1⁄3 as B + 1⁄3 at MT (mid-tillering) + 1⁄3 at PI.)), T_3:(1⁄2 as B + 1⁄4 at MT + 1⁄4 at PI.)), T_4:(1⁄4 as B + 1⁄4 at MT + 1⁄4 at PI + 1⁄4 at BT (booting)), T_5:(1⁄4 as B + 1⁄4 at MT + 1⁄4 at BT + 1⁄4 at CH (complete heading)), and T_6:(1⁄4 as B + 1⁄4 at MT + 1⁄4 at PI + 1⁄4 at F ( flowering)) on morpho-physiological attributes and grain yield of Egyptian hybrid rice (1) under broadcast seeded-rice. The results revealed that nitrogen levels caused significant increases in all morpho-physiological attributes and grain yield of Egyptian hybrid rice (1), except for number of primary branches/panicle, number of panicle/m², panicle weight and 1000-grain weight in both seasons. Leaf area index and dry matter production at flowering were significantly increased in first and second seasons, respectively, Increasing N-level up to 220kg N/ha significantly increased number of unfilled grains/panicle and straw yield t/ha. In addition, application of 165kg N/ha produced the highest values of number of filled grains/panicle, grain yield t/ha and harvest index in both seasons. Moreover, It was observed that the highest estimated values of dry matter production at panicle initiation and straw yield; and the lowest number of panicles/m² were recorded in the first treatment (T_1), without significant differences with the 〖(T〗_(3 )) and 〖(T〗_(5 )) treatments in both seasons. The highest dry matter production at flowering, LAI at flowering, chlorophyll content in flag leaf, days to 50% heading, plant height at harvest, number of primary branches/panicle, panicle weight, heaviest 1000-grain weight, harvest index and grain yield were exhibited in 〖(T〗_(6 )) in both seasons, The interaction between nitrogen levels and time of nitrogen application had significant effect on dry matter production ( g/m²) at panicle initiation, leaf area index at both panicle initiation and at flowering, chlorophyll content in flag leaf and number of tillers/m², number of filled grains/panicle in both seasons and number of unfilled grains/panicle in the second season. From the obtained results, it could be recommended that splitting of N-fertilizer application with the rate of 165 kg/ha in four equal doses i.e. as basal application, mid-tillering, panicle initiation and at the flowering stages were played a remarkable role for achievement of high yield production from Egyptian hybrid (1) rice genotype, when it grown under broadcast seeded rice under normal soil in Egypt.

RESPONSE OF EGYPTIAN HYBRID RICE 1 TO DIFFERENT SEED RATES AND NITROGEN LEVELS BY USING BROADCAST SEEDED METHOD.

Application of the optimal seed rate and adequate amount of nitrogen fertilizer led to increase productivity of hybrid rice under broadcast seed condition. Two field experiments were carried out during 2010 and 2011 rice growing seasons at the Experimental Farm of Rice Research and Training Center, Sakha, Kafr El-Sheikh, Egypt to study the response of Egyptian hybrid rice 1 to four seed rates, i.e. 5, 7.5, 10 and 12.5 kg seed fed-1 and five nitrogen levels, viz 0, 23, 46, 69 and 92 kg N fed-1 under broadcast seeded-rice. The results of this study can be concluded as follows: the seed rate of 7.5 kg seed fed-1 produced the highest mean values of chlorophyll content, dry matter accumulation and leaf area index (LAI (at 65 days after sowing (DAS), while after harvesting also, gave the highest mean values of number of filled grains panicle-1 and grain yield tons fed -1. The plots which planted with 10 kg seed fed-1 recorded the highest mean values of No. of tillers, No. of panicles m-2 without significant differences with the rate of 7.5 kg seeds fed-1, but the heaviest 1000 grain and panicle grain weight. Also, data revealed that Egyptian hybrid rice 1 response positively to application of nitrogen levels up to 92 kg N fed-1, which recorded the highest values of all traits. The highest grain yield was obtained when rice was grown at seed rate 7.5kg seeds fed-1and fertilized with 92kg Nfed-1.

Improved Lodging Resistance in Rice (Oryza sativa L.) Cultivated by Submerged Direct Seeding Using a Newly Developed Hill Seeder

Submerged direct-seeded rice is more susceptible to lodging during the ripening period than is transplanted rice. Comparing different seeding methods of direct seeding cultivation, lodging resistance is considered to be highest in hill-seeded rice. However, practical hill-seeders did not exist, and previously direct-seeding had been conducted by broadcast- or row-seeding. This paper discusses the development of a hill seeder and improvements in the lodging resistance of hill-seeded rice, both of which have contributed to the recent widespread cultivation of submerged, direct-seeded rice in Japan. The newly developed hill-seeder effectively drives seeds intermittently into the puddled soil and enabled establishment of a hill which is composed of several plants as is a transplanted hill. Hill-seeded rice showed remarkable higher pushing resistance than broadcast-seeded rice across a range of seedling density and seeding depth after heading, while the plant length was longer in hill-seeded rice. It is suggested that the high lodging resistance of the hill-seeded rice is derived from the larger number of panicles per hill, because the lodging resistance varied depending on the number of panicles in a hill. The area cultivated by hill-seeding has been increasing since 1998, in 2004, it occupied 25% of the total submerged direct-seeded area.

Improvement of Lodging Resistance in Submerged Direct Seeding Rice (Oryza sativa L.) Cultivation Using a Newly Developed 'Shooting hill-seeder'. Effect of seedling density on the lodging resistance of hill-seeded rice as compared with that of broadcast-seeded rice.

打込み式代かき同時土中点播機を用いた安定的湛水直播栽培法の確立のため, 異なる苗立ち密度(40, 80および160本m-2)における耐倒伏性を散播水稲と比較して点播水稲の耐倒伏性に関する特性解明を行った. その結果, 点播水稲は散播水稲に比較して稈が長くなるために稈基部にかかる力が大きくなるが, 有効茎歩合が高いために耐倒伏性に関連した稈の形質が優れること, 押し倒し抵抗値が顕著に大きいことにより稲株の耐倒伏性が強化され, 倒伏を生じにくいことが明らかとなった. また, このような播種様式間差は苗立ち密度の高い条件で顕著となった. 押し倒し抵抗値の変動要因を検討した結果, 散播水稲において1株穂数が10本以下の株は押し倒し抵抗値の変動が大きく, 1株穂数の減少により抵抗値が顕著に低下するのに対し, 1株穂数が10本以上の株は押し倒し抵抗が安定して高かった. このことから, 散播水稲では苗立ち密度40本m-2以上の条件では1株穂数が10本以下となるために, 苗立ち密度の変動により1株穂数が変動するのに対し, 点播水稲は標準的な播種条件(条間30cm, 株間20cm)では苗立ち密度が40～160本m-2(1株苗本数が2～10本)の間で変動しても1株穂数が20～26本と安定して多いことにより, 苗立ち密度が変動しても点播水稲の耐倒伏性が安定して高いものと推察された. 湛水直播栽培では苗立ち密度の変動が避けられないため, このような特性を有する点播栽培は湛水直播栽培の安定化に有効であると考えられる.

Growth Characteristics of Submerged Hill-Seeded Rice (Oryza sativa L.) in Warmer Regions of Japan. Difference of growth as compared with broadcast-seeded rice.

打込み式代かき同時土中点播機を用いた水稲の安定的湛水直播栽培技術を確立するための基礎的知見を得ることを目的に,散播および点播水稲の乾物生産や窒素吸収特性を比較し,生育や収量性との関連について検討を行った.複数個体で株を形成する点播水稲は株内の個体間競合を生育初期から生じるために,散播水稲に比較して初期分げつが少なく,最高分げつ期までの乾物増加量の低下を生じた.点播水稲では,このような初期生育の抑制により最高分げつ期から穂揃い期における窒素含有率が高まったこと,幼穂分化期以降の乾物重は散播水稲との差を生じなかったことにより,幼穂分化期の窒素吸収量が散播水稲に比較して増大した.しかしながら,点播水稲は散播水稲に比較して最高分げつ期から幼穂分化期の窒素含有率の低下が大きいために,窒素吸収量の増大にともなう総籾数の増加を生じなかったものと考えられた.また,点播水稲は成熟期のLAIが大きいこと,上位葉の面積当たり窒素含有量が高く,穂揃い期の個葉の光合成速度が高いこと等により登熟期間の乾物増加量が大きいことが明らかになった.このため,登熟性に優れる点播水稲は,窒素施肥法の改善による総籾数の増加にともない,収量性の向上が可能となることが示唆された.

Improvement of Lodging Resistance in Submerged Direct Seeding Rice (Oryza sativa L.) Cultivation Using a Newly Developed 'Shooting hill-seeder'. Method of hill-seeding for the improvement and stabilization of lodging resistance.

By using a newly developed 'Shooting hill-seeder', it is easy to adjust the hill space within a row or the seeding depth, and change the hill-seeding form in the submerged direct seeding rice cultivation. In this study, the effects of these seeding conditions on the lodging resistance of hill-seeded rice were examined. It was suggested that the increased hill space within a row resulted in lower lodging resistance because of the elongation of culm and decrease in pushing resistance of the hill. These results show the importance to adopt a variety with high lodging resistance, or to control the nitrogen uptake by improvement of fertilizer application or water management, when a large hill space is necessary. On the other hand, the hill-seeding form did not seem to affect the lodging resistance. Furthermore, in hill-seeded rice, the chance of shallow seeding is rare, and the degree of lodging due to shallow seeding is extremely small as compared with broadcast-seeded rice. These characteristics are very important for the stabilization of the submerged direct seeding cultivation, in which unification of the seeding depth is difficult, and the stabilization of seedling emergence is important.

Butachlor safener combinations for weed control in direct-seeded puddled rice

Weed competition is a major constraint to the productivity of broadcast-seeded rice. Although manual weeding controls weeds effectively, because of the absence of rows, it is difficult, time consuming, and costly. In addition, labor is scarce. Butachlor, the recommended herbicide, controls weeds effectively, but is toxic to germinating rice seedlings. The use of a safener, an antidote, protects rice seedlings from butachlor injury effectively without any adverse effect on weed control.

Influence of green manuring with Sesbania rostrata and Aeschynomene afraspera or urea on dynamics and uptake of nutrients by wetland rice

Nutrient concentrations in the soil and crop uptake from incorporated green manure and urea in flooded rice was studied in field experiments. Release of plant-available nitrogen (NH4 +-N) from green manure was slightly delayed compared with that from prilled urea (PU) because Sesbania rostrata L. and Aeschynomene afraspera L. released the N gradually after their decomposition, whereas N became available immediately after PU application. Exchangeable NH4 +-N concentration in soil peaked at 163 mg kg–1 in the transplanted rice (TPR) and 198 mg kg—1 in broadcast-seeded rice (BSR) at 0 and 1 week after PU application. Broadcast-seeded rice depleted NH4 +-N faster than did TPR because of the crop‘s vigorous growth in the former during the early stage. Soil solution NH4 +-N followed a similar trend to that of soil NH4 +-N. Incorporation of S. rostrata and A. afraspera increased the concentration of P, K+, Fe2+ and Mn2+ in soil solution more than did the application of PU. However, zinc concentration decreased in all treatments. Both PU and green manure increased the N status of the rice plants and enhanced the uptake of P, K, Fe, Mn and Zn by the rice crop. This suggests that application of green manures improves the uptake of these nutrients by the crop. The highest apparent N recovery was obtained with PU followed by green manure.

Nitrogen use efficiency of irrigated tropical rice established by broadcast wet-seeding and transplanting

Broadcast wet-seeding is gradually replacing transplanting in irrigated rice systems of Southeast Asia. Previous studies reported higher fertilizer-N use efficiency for broadcast-seeded than transplanted rice despite similar grain yields in treatments that received N fertilizer. To re-examine this issue, we compared crop performance and the recovery efficiency (er, Δ N uptake per unit N applied), agronomic efficiency (ea, Δ grain yield per unit N applied), and partial factor productivity from applied N (PFP, grain yield per unit N applied) in broadcast-seeded and transplanted rice across a wide range of N fertilizer rates at research stations and in farmers' fields. Rice crop established by broadcasting had more rapid leaf area development, dry matter accumulation, and N uptake than transplanting during vegetative growth stages, but slower growth rates and N uptake after panicle initiation, particularly during the grain filling period. Without applied N, grain yield and N accumulation at maturity were significantly lower in broadcast-seeded than transplanted rice, whereas yields and N uptake were comparable for both planting methods with equivalent rates of applied N. Although both er and ea were higher for broadcast-seeded than transplanted rice, this advantage was an artifact of lower yields and reduced N uptake by broadcasting without applied N rather than improved performance with applied N. In contrast, PFP values were similar for broadcast-seeded and transplanted rice at comparable fertilizer-N rates and in the absence of lodging. We conclude that the PFP from applied N provides a more relevant measure of N use efficiency of different crop establishment methods, and that the system-level N use efficiency of broadcast-seeded rice was not greater than that of transplanted rice.

Long-term effects of tillage, cultivar and herbicide on weed shift and control in broadcast-seeded flooded rice

Chemical and nonchemical control of a heterogenous weed community in broadcast-seeded rice was studied at the International Rice Research Institute farm from 1984 to 1986 during both dry and wet seasons. Increasing tillage frequency from one to three harrowings substantially reduced the stand of Paspalum distichum L. but increased that of Scirpus maritimus L. Increasing the number of harrowings from one to three also significantly increased yield. Cultivar type did not affect weed infestation, although IR29723-143-3-2-1 consistently outyielded IR36 in weed-infested plots. Bensulfuron-methyl (methyl-2[(4,6-dimethoxy-pirimidin-2-yl) aminosulfonyl-methyl] benzoate) and propanil (3′4′-dichloropropionanilide) + 2,4-D ((2,4-dichlorophenoxy) acetic acid) adequately controlled S. maritimus and the annual weeds Echinochloa glabrescens Munro ex Hook.f., E. crus-galli (L.) Beauv. ssp. hispidula (Retz.) Honda, Cyperus difformis L. and Monochoria vaginalis (Burm.f.) Presl, increasing yield significantly. However, herbicide application also significantly increased the P. distichum population. The long-term result from continuous tillage and herbicide use was an increase in weed population.