Weed Biology and physiology

AAU, Anand

Biology of Digera arvensis, Trianthema monogyna, Cyperus rotundus and Parthenium hysterophorus was studied in pots at 0, 2, 5, 10 cm depths. Seed germination of Digera, Trianthema monogyna and Parthenium was observed in 0 – 5 cm depth. No germination of Trianthema monogyna was recorded below 5 cm depth. Days to germination, days to first flowering, shoot and root fresh and dry biomass and total fresh and dry biomass were not influenced by depth of sowing. Parthenium produced flowers and seed at any time of the year under favourable conditions.

PJTSAU, Hyderabad

Biology of Cyperus rotundus and Celosia argentia in cropped area and Parthenium hysterophorus, Alternanthera spp. under non-cropped were studied. Alternanhera sp. and Celotia argentea did not germinate from 10 cm depth where as percent germination of Parthenium hysterophorus and Cyperus rotundus was 35 and 40, respectively. Celotia argentea germinated from 5 cm depth but Alternanhera sp. was able to germinate only from zero cm depth, Cyperus rotundus and Parthenium hysterophorus germinated from all the depths but more germination of Parthenium was observed from the top layers.

GBPAUT, Pantnagar

In winter 2014-15, biology of Phalaris minor, Medicago denticulata and Anagallis arvensis were studied.

Phalaris minor

Duration of vegetative stage of P. minor was 85 days while the reproductive stage was 35 days. Total duration was 180 days. Plant height increased from 80 cm at 5 DAS to 117.5 cm at 120 DAS. Tiller number was around 45 per plant at 85 DAS. At 85 DAS, biomass of P. minor plants was 47.8 g/plant which increased to 158.5 g/plant at 120 DAS. Average number of panicles per plant was 125. Number of seeds per panicle ranged between 398-480 depending upon the size of panicles. Relative growth rate and crop growth rate were 0.10 g/g/week during 60-67 DAE which decreased in next week (68-75 DAE) to 0.08 g/g/week. The crop growth rate was 9.73 g/m²/week during 60-67 DAE which increased in the next week to 14.36 g/m²/week.

Medicago denticulata

Duration of vegetative growth stage was 90 days while the reproductive stage was 30 days. Total duration up to maturity was 145 days. Average number of flowers per plant were 46 while the total number of fruits/plant was 1021. Each fruit possessed 3-5 seeds. There were 3063-5105 seeds in a single plant. RGR was 0.05 g/g/week during 60-67 DAE which decreased in the next week to 0.04 g/g/week (68-75 DAE). Average fruit number per plant was around 400. The fruits contained 3-5 seeds each. On an average around 1200-2000 seeds were present in a plant.

Anagallis arvensis

Duration of different growth stages of A. arvensis of vegetative stage was 25 days while the reproductive stage was 70 days. Total duration was 127 days. Plant height of A. arvensis was 7.1cm at 25 DAS which increased to 29.4 cm at maturity. Average number of flowers per plant was 23. Total number of fruits per plant was 449. Capsule shaped fruits had 20- 30 seeds. The total number of seeds per plant was around 8,980-13,470.

Echnichloa colona

Plant height of Echnichloa colona was 43 cm at 30 days after sowing and increased upto 108 cm at 75 DAS. Maximum numbers of tillers 49 per plant were recorded at 60 DAS which were reduced to 43 at maturity stage. Maximum number of leaves/plant (277) and leaf area (943.6 cm2/plant) was recorded at 60 DAS. At maturity, number of ears/plant was 58.2. Ear length was around 10.8 cm. Number of seeds/panicle was 308.4 and the 1000- seed weight was 0.88 g.

Echnichloa crus-galli

Plant height of Echnichloa crus-galli at 30 DAS was 61.4 cm which increased to 115.5 cm at harvest. Number of tillers/plant was 16.6 at 60 DAS which reduced to 14 at 75 DAS. Maximum numbers of leaves (105/plant) as well as leaf area (3971 cm2) were recorded at 75 DAS. At maturity, numbers of ears/ plant were 23.6 and the number of spiklets/spike was 18.8. Ear length was 17.4 cm. Numbers of seeds/panicle were 590.3 and the 1000- seed weight was 1.34 g.

BAU, Ranchi

A. Cropped area

Cyperus iria and Ludvigia parviflora were two most harmful weed of rice crop particularly in transplanted rice. Mean root shoot ratio of Cyperus iria was 8.2 and 5.0 with mean of 6.5:1. Cyperus iria flowered in the range of as early as 45 days after sowing to as late as 56 DAS during 2014 and 49.2 during 2015 while it matured in the range of 70 to 90 DAS during 2014 and 80 to 92 during 2015 with mean maturity duration of 79 and 84.75 DAS, respectively (Table 2.1a.1).

Non-cropped area

Detail biology of Cassia tora was carried out.

Table 2.1.a.1 Biological study of Cassiatora

Name of Weed	Days to flower		Days to maturity,		Number of branches		Number of pods / plant		No. of seed per plant,		Plant height (cm)
Cassia tora	2014	2015	2014	2015	2014	2015	2014	2015	2014	2015	2014	2015
1	45	54	85	95	5	6	21	22	21	20	40	45
2	50	45	95	90	5	4	11	25	23	15	53	60
3	54	50	90	110	5	4	15	20	22	15	46	65
4	55	50	85	95	6	5	15	15	20	20	45	45
Average	51	50	89	98	5	4.75	16	21	22	18	46	54

TNAU, Coimbatore

Cropped Situation

Trianthema portulacastrum

Trianthema portulacastrum emerged from 0 to 7.5 cm depth of soil and the emergence was higher in the top 2.5 cm of the soil. Flowering started 25-30 days after emergence. Seeds matured 15-22 days after flowering. Seed production was around 7000 – 7500 seeds / plant. Root weighs was about 0.16 g/ seedling. Stem was cylindrical, dichotomously branched, prostrate or trailing. Somewhat glabrous, at places reddish tinted, nodes swollen, fresh stem succulent in nature . The length varied from 10-25 cm. Shoot dry weight was about 2.27 g/plant. Flower were small, solitary, sessile, pinkish, nearly concealed by the pouch of the petiole, calyx tube scarious, thin, stamens 10-15 in number, ovary superior, sessile, style single papillose, shorter than the stamens. Fruit capsule was 3-5 mm long, almost concealed in the petiolar pouch, slightly concave, upper beak-like part at the time of dehiscence, carrying 2-3 seeds per capsule, lower cup-like part enclosing 2-5 or more seeds, fracture fibrous. Seeds are reniform in size, dull black, rough, muriculate seeds were present.

Amaranthus viridis

Amaranthus viridis emerged mostly from the top 2.5 cm of the soil profile, with few emerging seeds located deeper than one 2.5 cm. The seeds required adequate moisture and good seed soil contact to absorb moisture and germinate. More deeply buried seeds remain dormant. Root were slender, tapering, the length ranges from 10-12.5 cm at 30 DAS. Distinct reddish coloration on roots was observed. Newly emerging seedlings open a pair of long, narrow cotyledons followed by the first true leaves. Leaves were simple, petiolate (stalked) leaves arranged alternately (singly) on stems. Flowering started five to six weeks after emergence. Flowering to formation of seeds ranged from 7–12 days. Flowers were arranged in terminal or axillary. Panicle was elongate in nature. Seed were smooth shiny and lens shapped.

Non-cropped area

Abutilon indicum

Emergence of A. indicum was maximum at a depth of 1-4 cm. Tap root system, fairly long with a number of lateral branches, 1.5-2 cm in diameter, light brown, outer surface smooth with dot like lenticels were present. Abutilon indicum is medium sized, branched perennial shrub and grows upto 2 meter. Plant covered with minute hairs. Leaves were alternate, cordate and acute. Stem was round, softly tomentose and often tinged with purple. Inflorescence was solitary axillary. Flowers were yellowish with 5 petals, corolla yellow, about 3 cm in diameter. Fruits have 15-20 chambers, arranged spirally. Reniform, blackish-brown, minutely pitted and stellate-hairy. Seed was blackish brown in color.

AAU, Jorhat

In 2015, response of Panicum repens Linn. was studied against different doses of glyphosate. Total dry matter of Panicum repens varied from 828 to 952 g/m2 and total underground rhizomes varied from 392 to 462 g/m2 quadrate in the untreated (control) plots. Glyphosate 1 kg, with or without 2% juggery, reduced the aerial parts of P. repens significantly at 30 days. However, in the later stages, glyphosate 0.75 kg followed by glyphodate 0.75 kg applied 15 days after first application mixing with 2% juggery gave much better reduction of aerial biomass and result was at par with single application of higher dose of glyphosate (1.5 kg). Regeneration was observed in all the plots nearly after 50 days of herbiciden application. Sequential application of glyphosate was found more effective than single application.

IGKV, Raipur

Biology of Echinochloa colona, Ischaemum rugosum (cropped) and Parthenium hysterophorus and Cassia tora ( Non-cropped) during Kharif 2015 were studied.

In cropped area, Ischaemum rugosum produced 9 g seed/plant against 4.8 g/plant by Echinochloa colona. Amongst non-cropped weeds, Cassia tora produced 18.2 g seed/plant as against 7.6 g/plant by Parthenium hysterophorus (Table 2.1a.3).

UAS, Raichur

Biology of Alternanthra sessilis, Cynotis cuculata (cropped), Parthenium hysterophorus and Cassia tora (Non-cropped) during late Kharif season of 2015 was studied. Seed germination of all the four weeds was influenced by depth of sowing. Germination was observed in 0 to 5 cm depth, while in 10 cm depth germination was almost zero. Parthenium hysterophorus took 42-43 days for flowering and matured in 92 t0 100 days while Cassia tora started flowering starts after 50 days and matured in 95 days.

KAU, Trissur

Pennisetum is a major wasteland weed of Kerala. It is also a fodder species with high nutritive value growing wild in the wastelands of the state. In Kerala, Pennisetum pedicellatum Trin and Pennisetum polystachyon (L) Schult. were two species widely seen. Pennisetum pedicellatum and polystachyon seem to be fast spreading in the waste lands, mainly on the sides of the national highways of Kerala. Weed dispersal was mainly by wind, road traffic and by soil transportation for construction and road construction. This weed has become a major cause for summer fires (Table 2.1a.4 and 2.1a.5).

Highest germination was observed between 25 to 28°C and declined when the temperature was 40°C. Weed germinates only after the peak summer season and flowers during short day condition in September and October in the state.

Tithonia diversifolia

Tithonia diversifolia forms dense stands and prevents growth of the native flora. Flower heads were solitary on a peduncle 6-13 cm long, and yellow in colour. Plants were seen in dense stands with a number of branches and each mature stem bear several flowers at the top of branches. Seeds were achenes, 4-8 mm long and topped with a ring of scales and two awns. Seeds were blackish in colour and are somewhat four-angled. In Kerala the main flowering period is from October to March – April.

Allelopathic response of Tithonia diversifolia was tested on greengram seeds. Highest response was observed with the 10% solution. Cold water extract of weed was capable of slightly inhibiting germination and growth of greengram which was not significant. However, the total seedling length and vigour index showed significant reduction indicated that Tithonia was capable of suppressing other species and can be a threat to the biodiversity of the state (Table 2.1a.6).

Isachne miliacea

Soil type had an influence on the phenology of I. miliacea. Due to high acidity and salinity, seeds sown in Pokkali soils did not germinate. In Kuttanad soil seeds germinated within 5 to 8 days, while in Onattukara soil and Kole land soil, germination started on the 8th day. Seed sown in Palakkad soil started germination by the 12th day. Days to tillering also varied with the soil type and found in the range of 13-17 days. Seedlings from Onattukara soil started tillering by 15-28th day and continued up to 60 days. Seed formation and maturation varied with soil type. Plants dried after seed maturation. Seed production was comparatively higher in plants from Kuttanad soil at 45 DAS to maturity stage (41 -76.8).

Propagation of I. miliacea using both seeds and stem cuttings was influenced by depth of burial, moisture level, temperature and light. When the seeds were on the soil surface all the seeds germinated (100%) while only 42 % of the seeds germinated when placed at a depth of 2 cm. None of the seeds placed at 10 cm depth germinated. Light has a significant influence on the germination of I. miliacea. Pots placed in open condition had the highest germination (100%) than under 50 % shade. Highest germination was observed at 25oC (72 %) followed by 20oC (56%) and 30oC (54%). Lowest germination of 20% and 22% were observed at 40 oC and 15 oC, respectively (Table 2.1a.7 and 2.1a.8).

Monochoria vaginalis

This weed was found to germinate only in submerged/ saturated soil and was not seen in dry condition. Water was a prerequisite for germination of the weed. Under submerged conditions, seedlings emerged within 15 days, Seedling emergence was higher when the seeds were exposed to light than when buried inside the soil. The weed is rarely seen in dry sown condition.

Fig.1 Flower fruit and seedling of M.vaginalis

NPK content of the weed was higher as compared to the rice plant except the P content in M. vaginalis grown in Moncompu soil. This might be because the P content in Moncompu soil was comparatively lower. Absorption of nutrients by the weed was associated with the availability of nutrients and the pH of the soil, which accounts for the variation in morphological attributes of the weed seen in different rice growing areas of Kerala.

BAU, Ranchi

Weedy rice from various farmers fields were collected during 2014 and grown in pots for detailed morphological growth parameters (Table 2.1b.1)

RAU, Pusa

Infestation of weedy rice was found in direct seeded deep water rice in Darbhanga and Madhubani districts of Bihar and they are locally known as Jharang or Lalsar. Weedy rice has the plant height 85- 95 cm, No. of tillers /plant 11-22, effective tillers/ plant 5-14, number of grains / panicle 27-70, length of panicle 9-22 cm and reduction in grain yield of rice varied from 27-48 %. All the weedy rice found were awned. Species wise dominancy of weedy rice in the rice field were in the order of Oryza rufipogan > Oryza spontanea.

UAS, Bengaluru

No problem of weedy rice in paddy cultivation in an alrming scale. However, monitoring was done in the rice fields for incidence of weedy rice.

NDUAT, Faizabad

Three species of weedy rice viz. Oryza nivara, O. sativa F. spontanea and O. rufipogon were found in the phyto-sociological survey of weedy rice in rice fields in Amethi, Jaunpur and Varanasi districts of eastern Uttar Pradesh. Among the three weed species, Oryza sativa f. spontanea was the most dominant species in Amethi and Varanasi districts with a weed density of 19.5-28.2 plants/m2, relative density of 42.9-43% and IVI values ranged from 59.9- 98.2%. But in case of Jaunpur district, O. spontanea was found most dominant species followed by O. rufipogon. Oryza nivara and O. rufipogon. Farmers also explained the severity of these weed species and told that O. rufipogon and O. spontanea are being observed in the crop fields only from last 3-4 years.

PAU, Ludhaina

During Kharif 2015, two different accessions of weedy rice were sown. Data pertaining to these studies is given in Table 2.1b.2 as below:

WS 2.1.c(i) Inheritance of resistance against alternate herbicides in various biotypes of P. minor

CCSHAU, Hisar

Seeds of uncontrolled P. minor were collected from farmers’ fields in different districts of Haryana during Rabi 2014-15. These biotypes along with biotype from RRS, Uchani, Karnal as susceptible check were sown in pots during Rabi 2014-15. Spray of graded doses (½X, X and 2X) of herbicides (clodinafop, sulfosulfuron, mesosulfuron+ iodosulfuron and pinoxaden) was done at 30 DAS (2-4 leaf stage). Clodinafop and sulfosulfuron at X dose were effective (>80% control) against 9 biotypes, and mesosulfuron + iodosulfuron and pinoxaden against 17 biotypes. Efficacy of mesosulfuron + iodosulfuron and pinoxaden against majority of the biotypes from farmers’ fields indicated their suitability in management of herbicide resistance in P. minor. Clodinafop and sulfosulfuron were not effective (<20% control) against five and one biotypes, respectively. All the biotypes were effective against the Uchani biotype (susceptible check).

WS 2.1.c (ii)Management of herbicide resistant P. minor in wheat at farmer’s fields

CCSHAU, Hisar

Sequential application of pendimethalin 1.5 kg/ha PRE followed by tank mix pinoxaden+ metsulfuron 64 g/ha or mesosulfuron+iodosulfuron 14.4 g/ha POE provided excellent control of P. minor as well as broadleaf weeds. Although, in the absence of pendimethalin PRE, pinoxaden+metsulfuron 64 g/ha POE, mesosulfuron+iodosulfuron 14.4 g/ha POE and s e que n t i a l appl i c a t i o n o f sul f o sul fur o n 25 g/ha followed by pinoxaden 60 g/ha were effective against P. minor but some yield reductions were noted. Alone PRE application of pendimethalin + metribuzin was effective against P. minor at higher dose but due to the toxicity of metribuzin on wheat significant reductions in yield was recorded. PRE pendimethalin 1.5 kg/ha followed by pinoxaden + metsulfuron 64 g/ha significantly reduced P. minor density as compared to PRE pendimethalin + metribuzin at both doses. Similar trend was observed in grain yield of wheat.

Sequential application of pendimethalin 1000 g/ha (PRE) fb clodinafop 60 g/ha, sulfosulfuron 25 g/ha, mesosulfuron+ iodosulfuron (RM) 14.4 g/ha or pinoxaden 50 g/ha at 35 DAS provided almost complete control of Phalaris minor along with effective control of broadleaf weeds. Sequential treatments resulted in high grain yield of wheat (5.3-5.4 t/ha) as compared to post-em herbicides alone (4.8-5.0 t/ha). The B: C ratio also increased from 0.07-1.1 to 1.1-1.1.

PAU, Ludhiana

Isoproturon, fenoxaprop, clodinafop recorded highest GR values (Table 2.1c.2). 50 Calculated GR and associated RF indicated different 50 levels of resistance to herbicides. P. minor showed very high level of resistance to fenoxaprop, isoproturon and clodinafop, low level to pinoxaden, sulfosulfuron and pre-mix of mesosulfuron and iodosulfuron, and no resistance to pre-mix of fenoxaprop+metribuzin and metribuzin. The results indicated that this biotype has developed multiple-resistance.

KAU, Thrissur

After spraying herbicides, all the weeds dried within two weeks in all the treatments. They were then regularly irrigated and the germination count of C. rotundus was taken on 50th, 75th, 125th and 150th day after spraying. The maximum number of weeds was seen in the control treatment followed by 2, 4-D amine salt 125 g/ha. Lowest weed count was observed in 2, 4-D amine salt 125 g/ha fb glyphosate 750 g/ha and glyphosate 1.5 kg/ha. Herbicide sprays were repeated in all the treatments and after two weeks when the plants were completely dried the tubers were excavated and the number and weight of the tubers in each treatment was counted. Fifty tubers initially planted had multiplied to 226 tubers in the control while there was drastic reduction in the number of tubers in all other treatments.

Among the treatments, glyphosate 1.5 kg/ha and 2,4-D amine salt 125 g/ha fb glyphosate 750 g/ha were the best treatments both in the field and under controlled conditions.

UAS, Raichur

Application of glyphosate 3 kg/ha was found most effective in controlling cyperus rotundus indicated 89.5% shoot mortality. Regeneration of shoots was lower with the 3 kg/ha treated plot at both 40 and 80 DAS (2.3 and 3.2 out of 10) as compared to control (8.7 and 9.7 out of 10). This treatment was followed by application of glyphosate 1.5 kg/ha (3.3 and 4.3 out of 10) and 2,4-D amine salt (125 g/ha) to induced senescence for 48 h followed by glyphosate 750 g/ha (3.7 and 4.7 out of 10) were the next best treatments in suppressing the growth of Cyperus rotundus. Viability was more with the tubers present at deeper depth (15 cm) as compared to lower depth (5 cm). Significantly higher viability of tubers was noticed with application of 2,4-D amine salt 125 g/ha at 10 and 15 days after sowing (3 and 4 out of 5) as against application of glyphosate3 kg/ha (1.3 and 1.7 out of 5).

PAU, Ludhiana

All herbicide treatments significantly reduced Cyperus shoot populations, tuber number and tuber weight. 2,4-D amine salt 125 g/ha for 48 h followed by glyphosate 750 g/ha was most effective in controlling C. rotundus followed by glyphosate 1500 g/ha. Minimum tuber number and tuber weight per m² was observed in 2,4-D amine salt 125 g/ha for 48 h followed by glyphosate 750 g/ha. Minimum number of tubers sprouted in treatments where tubers were collected from experimental plots treated with 2,4-D amine salt 125 g for 48h followed by glyphosate 750 g/ha, and glyphosate 1500 g/ha.

GBPUAT, Pantnagar

Effect of glyphosate and 2, 4-D at different doses to control Cyprus rotundus was evaluated during rainy season 2015. Percent mortality was highest in the glyphosate treatments. It ranged from 65.8% at 0.75 kg to 77.6 % at 1.5 kg. It was reduced to 51.7% when treated with 2, 4-D at 0.5 kg/ha alone. Combined application of 2,4-D (0.125 kg) and glyphosate (0.75kg) recorded 52.2% mortality. Lowest regeneration (7%) was recorded with glyphosate 1.5 kg followed by its lower dose or combined application of glyphosate and 2,4-D (14-15%). Tubers viability was lowest (6.6%) in the 2,4-D treatment (0.125kg).

TNAU, Coimbatore

Performance of glyphosate on propagation potential of C. rotundus was evaluated. In the experimental field, sedge weed mortality was found higher with the application of glyphosate at 1.5 kg/ha and it was followed by the application of 2,4-D amine salt (125 g/ha) to induce senescence for 48 h followed by glyphosate 750 g/ha. Higher density of C. rotundus was recorded with 2,4-D amine salt (125 g/ha) treated plot (Table 2.1d.1). Primary and secondary tubers from glyphosate applied 1.5 kg/ha were not regenarted. Tertiary tubers were regenerated only after 45 days after herbicide spray.

WS 2.2.1 Impact of climatic regime on changes of weed flora composition

AAU, Jorhat

Transplanted Kharif rice fields of eight blocks of Jorhat district were surveyed during 2015 and it was compared with that of 1991 to find out weed shifts and other changes in floristic composition. Cyperus iria dominated the crop at early part of its life span in almost all the blocks. Amongst the grasses, Isachne himalaica was recorded as the most dominant and common weed. Weed species prevalent in 1991 in the transplanted Kharif rice ecosystem at Jorhat district, but not recorded in 2015 were Cyperus distans, Cyperus pilosus, Hemarthria protensa, Leersia hexandra, Penicum repens, Sacciolepis interrupta, Centala asiatica, Eichhornia crassipes, Enhydra fluctuans, Polygonum posumbu, Valisnaria natans and Ludwigia octevalvis.

Fig. 2.2.1.1 Comparative cumulative density, number of species and sum dominance ratio of different groups of weeds between 1991 and 2015 in transplanted rice ecosystem at Jorhat district

WS 2.2.3 Threshold study of dominant weed species

AAU, Jorhat

Cyperus iria and Echinochloa crus-galli obligate weeds of rice were selected for the study. Densities of both the weeds were 0, 10, 20, 30, 40, 50, 60, 70, 80, 90,100, 110, 120 and 130. Desired population density of these weed species were maintained up to 80 days after transplanting by manual uprooting of all other weeds.

Echinochloa crus-galli: Rice var. Ranjit had maximum stuture of around 108 cm and the stature of Echinochloa was around 103 cm in their vegetative stage. Total number of tiller of rice per square meter area did not differer significantly because of competition with the weed; but the panicle/m² was the highest under zero competition (404.3), which was at par up to the weed density 40/m² and 19.6% reduction of panicle number had significant difference in case of the variety Ranjit. Grain yield of the crop varied from 2917 to 5800 kg/ha and straw yield from 6854 to 13630 kg/ ha. Rice yield under Echinochloa density from 0 to 60/m2 did not possessed significant difference with the highest yield, beyond which the yield reduced drastically. Significant yield reduction started at the weed density 70/m2 and therefore, this density of E. crus-galli can be considered as the threshold limit in transplanted khrif rice (var. Ranjit).

Cyperus iria: Cyperus iria maintained at 1.0 to 0.7 raio in stature with its associated rice variety Ranjit. Weed dried up after 80 to 90 days after transplanting of rice and disappeared from the field after around 100 DAT releasing quite a huge amount of seeds in the crop field. Increase in weed density did not affect its height; but, its abundance in the rice field in the critical period of crop-weed-competition resulted in the reduction of paddy yield from 3 to 56%. Crop yield up to the C. iria density 90/m2 was at par with that of zero competition plots. Weed density 100/m2was found to be the threshold level which was responsible for 32.5% grain yield loss of the transplanted Kharif rice var. Ranjit and that loss was statistically significant.

 

WS 2.2.4 Weed suppressing ability of upland direct seeded rice varieties

AAU, Jorhat

Eight local rice varieties, Kopili, Meghi, Guni, Kolong, Disang (Improved), Sahabhagi, Inglongkiri and Maizubairon were tested during autumn 2015. Variety Maizubairon produced the highest LAI (20.01), which was at par with var. Inglongkiri and Guni; var. Disang and Kolong produced the least LAI. Interestingly, LAI between weedy and weed free treatments did not differ significantly. Crop duration was shortest in var. Guni followed by var. Meghi, and that was 90 and 93 days, respectively. Digitaria setigera and Eleusine indica prevalence was recorded from the very beginning. Broadleaved weeds, Ageratum houstonianum, Commelina diffusa, Ludwigia linifolia, Melochia corchorifolia and Physalis minima, Borreria articularis and Mikania micrantha were recorded after 60 DAS. Amongst the sedges, Cyperus sp. C. pilosus, C. rotundus, Fimbristylis bisumbellata and Scleria terrestris were common. Variety Inglongkiri, performed the best in plains by yielding 2.9 t/ha grain and showing better weed suppressing ability with the help of its better canopy coverage, in the direct seeded upland condition of autumn season, when rice in Assam suffered from heavy competition of weeds coupled with several supplementary weed originated problems.