Cyperus Difformis Research Articles

Sensitivity Analysis of Alisma plantago-aquatica L., Cyperus difformis L. and Schoenoplectus mucronatus (L.) Palla to Penoxsulam

Determining the intra-specific variability of response to a given herbicide is important for monitoring the possible shifts in the sensitivity of weed populations. This study describes the responses of populations of Alisma plantago-aquatica, Cyperus difformis, and Schoenoplectus mucronatus from Italy, Greece, Portugal, and Spain to penoxsulam, an acetolactate synthase (ALS) inhibitor widely used in rice. To evaluate previously evolved resistance to ALS inhibitors, sensitivity to azimsulfuron and bensulfuron-methyl was assessed. Dose-response experiments with penoxsulam were performed in a greenhouse simulating paddy rice field conditions. Log-logistic dose-response curves were used to estimate the ED50, ED80, ED90 and GR50, GR80, and GR90. To calculate the average ED and GR and assess the intra-specific variability, an artificial resampling method was performed. Populations ALSPA 0364, 0365, 0469, 0470, 0471; SCPMU 0371, 0475, 0267; CYPDI 0013, 0431, 0432, 0433 appeared to be resistant to sulfonylureas, while a higher sensitivity to penoxsulam was observed, while populations ALSPA 0363, CYPDI 0223 and SCPMU 9719 proved to be cross-resistant. Regardless of species, ED90 of susceptible populations were below penoxsulam label dose (40 g ai ha−1) while they reached values higher than 320 g ai ha−1 for resistant populations. Average GR50 were generally lower than ED50. Sensitivity variability among susceptible populations is relatively low, allowing for discrimination between susceptible and resistant populations, and previously evolved resistance to sulfonylureas can influence sensitivity to penoxsulam.

Sensitivity of Annual Weeds against Sulfentrazone 48 SC herbicide in Rice Cultivation

Herbicides are used successfully for weed control in rice fields for rapid effect, easier to application and low cost involvement in comparison to the traditional methods of hand weeding. Sulfentrazoneis a new pre-planting herbicide in Bangladesh. Field trials were conducted at Bangladesh Rice Research Institute (BRRI), Gazipur during Aman 2014 and Boro 2014-15 to evaluate the efficacy of sulfentrazone 48 SC on weed suppression and performance of transplanted rice. Treatments were Sulfentrazone 48 SC @ 150, 200 and 250 ml ha-1, pretilachlor 500 EC @ 1000 ml ha-1, weed free and unweeded control. Visual assessment indicated that this herbicide possesses high selectivity and not toxic to rice plants. The results revealed that the major weed flora associated with the transplanted rice was mainly comprised of two grasses, two sedges and four broadleaves in Aman 2014 and two grasses, two sedge and two broadleaves in Boro 2014-15. The most dominant weeds were Cyperus difformis, Echinochloa crus-galli, Scirpus maritimus and Monochoria vaginalis in both the growing seasons. Application of Sulfentrazone 48 SC @ 200 ml ha-1 was most effective to suppress weed density and dry masses in both the seasons resulting increased grain yield more than 50% as compared to unweeded control. Therefore, Sulfentrazone 48 SC @ 200 ml ha-1 should apply two or three days before plantingfor effectively control weeds in riceBangladesh Rice j. 2017, 21(1): 67-76

Effect of Selected Water Quality Properties on the Occurrence and Distribution of Aquatic Macrophytes in the Floodplains of River Benue at Makurdi

A study was carried out in River Benue and 10 sites constituting the floodplains of River Benue to determine the effects of selected water quality parameters on the incidence and infestations of aquatic macrophytes. All water quality properties were analyzed using Standard Procedures. Water pH was observed to be variable, ranging from 5.7 at River Benue at the point at which effluents from BBL are discharged to 7.8 at River Benue. Odour, turbidity, dissolved oxygen, (DO), total dissolved solids (TOD), biochemical oxygen demand (BOD) and chemical oxygen demand (COD), respectively also followed the same trend. No significant relationships existed between the occurrence and density of Azolla pinnata, Cyperus difformis, Kyllinga pumila, Pycreus lanceolatus (Poir.), Ludwigia decurrens, Leptochloa caerulescens Steud., Cardiospermum heliocacabum, Myriophyllum aquaticum, Pistia stratoites, Mariscus longibracteatus, Heliotropium indicum Linn., Sphenoclea zeylonica Gaertn.and Melochia corchorifolia and the water quality parameters at the study locations. However, positively significant relationships existed between the occurrence and density of Cyperus erecta and the pH of the water at River Benue and the amount of dissolved oxygen (DO) in water at the time of collection. There was a positive and highly significant relationship between Polygonium lanigerum R.Br., Heliotropium indicum, Persicaria decipens and Biochemical DO, BOD, COD and COD. Also, a positive and highly significant relationship existed between Ludwigia hyssopifolia and Sacciolepis africana with turbidity of water. The relationship to dissolved oxygen at time of water collection indicated the favorable disposition of these weeds to thrive and do well under conditions of relatively higher dissolved oxygen.

Management of penoxsulam- and bispyribac-resistant late watergrass ( Echinochloa phyllopogon ) biotypes and rice sedge ( Cyperus difformis ) in rice

Management of penoxsulam- and bispyribac-resistant late watergrass ( Echinochloa phyllopogon ) biotypes and rice sedge ( Cyperus difformis ) in rice

Potential allelopathic effects of rice plant aqueous extracts on germination and seedling growth of some rice field common weeds

Given the increasing emphasis on sustainable agriculture, and concerns about the adverse effects of extensive use of farm chemicals, research attention is now being focused on reducing the dependence upon synthetic herbicides, and finding alternative strategies for weed management. Allelopathic properties of crop plants may allow us to use lower amounts of herbicides with benefits for the environment and human health. Considering these aspects, the present study was conducted to investigate the allelopathic effects of six selected rice varieties (WITA-3, WITA-4, WITA-12, Woo-Co, Fukuhibiki and Kalizira) collected from Bangladesh Rice Research Institute (BRRI) on seed germination and seedling growth of five weed species; Echinochloa crus-galli, Cyperus difformis, Cyperus iria, Fimbristylis milliacea and weedy rice. The aqueous extracts of all the rice cultivars caused inhibitory effects on seed germination and seedling shoot-root length of all the weed species. However, the inhibitory effects of different rice varieties varied significantly based on the differences of weed species and weedy rice found to be the least affected compared to other weeds. WITA-12 resulted about 50% germination inhibition, 25% shoot length reduction and 23% root length reduction respectively compared to control. On the basis of average percentage inhibition, rice varieties ranked in order; WITA-12>WITA- 4>Fukuhibiki>Kalizira>Woo-Co>WITA-3. Our results suggested that there is a possibility of developing a new ecological weed management strategy using rice cultivars with higher allelopathic potentials. This means breeding of rice cultivars with higher allelopathic potential may provide natural and sustainable weed management options for rice growers.

Weed flora of aerobic rice and their effect on growth, yield and nutrient uptake by rice Oryza sativa in the coastal region of Karaikal of Puducherry, India

A field experiment was conducted at farm lands of Pandit Jawaharlal Nehru College of Agriculture and Research Institute, Karaikal to know the weed floristic composition and their effect on growth, yield and nutrient uptake by aerobic rice (Oryza sativa). The results revealed that totally 29 species of weeds from 22 genera belonging to 17 families were noticed. Among them, four were grasses, six were sedges, and nineteen were broad leaved weeds. Of this 29 species, four were perennials, and the rest were annuals. During initial stages (30 DAS), sedges dominated (38.3%) whereas at later stages (60 DAS) broad leaved weeds dominated the aerobic rice fields (42.5%). Grasses were found to be comparatively less dominant at both the stages. Echinochloa colona Link. (28.1%) followed by E. cruss-galli (L.) Beauv. (6.1%) among the grasses; Cyperus difformis L. (19.8%) followed by C. iria L (9.9%) among the sedges and Ludwigia abyssinica (28.0%) among the broad leaved weeds, were the predominant weed species in aerobic rice cultivation. Weeds, when left unchecked, competed with rice for all resources like nutrients, space, light and soil moisture. The unweeded control recorded the maximum nutrient depletion by weeds (76.6, 6.4 and 106.8 Kg of N, P andK ha-1 ). Due to severe competition, weeds suppressed the growth of rice which resulted in lower growth and yield attributes leading to lower grain (333 kg ha-1 ) and straw yields (1903 kg ha-1 ).

Florpyrauxifen-benzyl Weed Control Spectrum and Tank-Mix Compatibility with other Commonly Applied Herbicides in Rice

AbstractFlorpyrauxifen-benzyl is a new herbicide being developed for rice. Research is needed to understand its spectrum of control and optimal tank-mix partners. Multiple greenhouse and field experiments were conducted to evaluate florpyrauxifen-benzyl efficacy and tank-mix compatibility. In greenhouse experiments, florpyrauxifen-benzyl at 30 g ai ha–1provided ≥75% control of all weed species evaluated (broadleaf signalgrass, barnyardgrass, Amazon sprangletop, large crabgrass, northern jointvetch, hemp sesbania, pitted morningglory, Palmer amaranth, yellow nutsedge, rice flatsedge, smallflower umbrellasedge), and control was similar to or better than other herbicide options currently available in rice. Barnyardgrass was controlled 97% with florpyrauxifen-benzyl at 30 g ha–1, ultimately reducing height (86%) and aboveground biomass (84%). In these field studies at 30 g ha–1, no antagonism was observed when florpyrauxifen-benzyl was tank-mixed with contact (acifluorfen, bentazon, carfentrazone, propanil, and saflufenacil) or systemic (2,4-D, bispyribac, cyhalofop, fenoxaprop, halosulfuron, imazethapyr, penoxsulam, quinclorac, and triclopyr) rice herbicides. Although not every tank-mix or weed species was evaluated, the lack of antagonistic interactions herein highlights the flexibility and versatility of this new herbicide. Once florpyrauxifen-benzyl becomes commercially available, it will be beneficial to tank-mix this new herbicide with others without sacrificing efficacy, so as to apply multiple sites of action together and thus lessen the risk for evolution of herbicide resistance.

Weed control by pyrazosulfuron-ethyl and its influence on yield and economics of transplanted rice

A field experiment was conducted on a silty clay loam soil at Palampur, Himachal Pradesh during Kharif 2016 and 2017 to assess pyrazosulfuron-ethyl as an alternative herbicide to manage weeds in transplanted rice. Ten treatments comprised of company released sample of pyrazosulfuron-ethyl at 10, 15, 20 and 30 g/ha was compared to its market sample at 10 and 15 g/ha, bispyribac-sodium at 20 and 40 g/ha, hand weeding twice and weedy check. Pyrazosulfuron-ethyl and bispyribac-sodium effectively reduced the biomass of Echinochloa colona, Echinochloa crusgalli and Cyperus difformis. These herbicides also suppressed the growth of Ammannia baccifera, but not to the extent as hand weeding twice. Pyrazosulfuron-ethyl curtailed Eclipta alba, but lower dose of bispyribac-sodium was not effective against it. In 2016, pyrazsulfuron-ethyl 20 g/ha gave significantly higher yield while in 2017, pyrazsulfuron-ethyl 30 g/ha gave significantly higher yield of rice over other weed control treatments. Every gram weed biomass increase per square metre caused 5.6 kg/ha yield reduction of transplanted rice. Samples of pyrazosulfuron-ethyl obtained directly from the industry had an edge over the market samples. Weed persistence index was found to be decreased and crop resistance index increased corresponding to increase of dose of pyrazosulfuron-ethyl and bispyribac-sodium. The minimum weed index was under company's pyrazosulfuron-ethyl at 20 g/ha followed by 15 g/ha, 30 g/ha and market's sample at 15 g/ha. Cost of weed control was 3.0 to 4.7% of the total cost with pyrazosulfuron-ethyl and 6.1 to 9.8% with bispyribac-sodium. Company procured pyrazosulfuron-ethyl at 15 and 20 g during 2016 and at 20 and 30 g/ha during 2017 had higher net returns and marginal benefit cost ratio (MBCR). Eighty per cent of applied pyrazosulfuron-ethyl got degraded within 5 days of its application. Residues of pyrazosulfuron-ethyl in grain and straw at the time of harvest were below detectable level (BDL) irrespective of treatments.

Weed composition study on wheat and boro rice in research and farmers’ fields

A weed survey was conducted in Agronomy Field Laboratory, BAUFarm and farmers’ fields of Sutiakhali Natunchar village in Mymensingh district during the period from December 2015 to March 2016 to study the weed vegetation in wheat and boro rice. Ten fields were selected for each crop from each location. A quadrat of 0.25 m2 was placed randomly at four places in each plot and the weeds within the quadrat were identified and counted species-wise. The results revealed that the composition of weed species in two different crops was different and the composition of weed flora in each crop under different locations was also different. In wheat, a total number of 29 weed species belonging to 16 families were found from all three locations. The infesting weed species were 18 in Agronomy Field Laboratory, 16 species in BAU Farm and 19 species in farmers’ fields. From the five most dominant species, Polygonum hydropiper had the highest relative abundance value in both Agronomy Field Laboratory and BAU Farm and on the other hand, in farmers’ field, a new weed species, Eleusine indica was in the top most of the dominant list. The other weed species which were present in the dominant list of three locations were Cynodon dactylon, Cyperus rotundus, Paspalum distichum, Chenopodium album, Marsilea quadrifolia and Leucas aspera. In boro rice fields, among the three locations, 25 weed species were observed in total belonging to 13 families. Of which, 20 weed species were found in both Agronomy Field Laboratory and BAU Farm whereas in farmers’ fields, 21 weed species were identified. In both Agronomy Field Laboratory and BAU Farm, Eleocharis atropurpurea had the highest abundance value but in farmers’ field, Cyperus difformis occupied the highest value. The other dominant weed species were Leersia hexandra, Monochoria vaginalis, Echinochloa crusgalli, Paspalum distichum and Alternanthera philoxeroides found in three locations. Many common weeds were present in three locations in a crop but their frequency, uniformity, density and relative abundance value were different. The similarity index of weed species between wheat and boro rice indicated that the infesting weed species between the two crops was less associated. Thus the weed divergence in boro rice with wheat was high. From this study it was clear that the weed infestation was changed by crop and locations. In this study a little bit divergence and ranking of five most abundant weed species and low similarity index value of weed species in different crops under a specific area or among the area indicated that weed control measure should be adopted on crop basis in a specific area considering the dominant weed species.J. Bangladesh Agril. Univ. 15(2): 148-157, December 2017

Effect of Nitrogen Levels and Weed Management on Yield Performance of BRRI Hybrid Dhan3 Under AWD Irrigation System

Experiment was carried out at the Agronomy field of Bangladesh Rice Research Institute, Gazipur, during the period from December 2014 to May 2015 to investigate the response of different levels of N and methods of weeding on weed abundance and grain yield of BRRI hybrid dhan3 under alternate wetting and drying (AWD) irrigation condition. The treatments consisted of five N levels viz.,0, 60, 120,180 and 240 kg N ha-1 and four different weed control methods viz., Pre-emergence herbicide followed by 1HW, Pre-emergence followed by post emergence herbicide, Weed free by 3 hand weedings and Unweeded (control). The experiment was laid out in factorial RCB design with three replication. Pre-emergence application of prefer 18WP (Bensulfuran Methyl + Acetachlor) and post emergence herbicide Dhaman 300wp (Bispyribac sodium 18% + Bensulfuran methyl 12%) followed by one hand weeding effectively control all weeds (78-93%). In the experimental field, sedges and grass weeds were highly dominant over treatments. Based on summed dominance ratio (SDR), the most dominant weed species could be arranged in the order of Echinochloa crus-galli > Scirpus juncoides > Cynodon dactylon > Cyperus difformis > Marselia minuta > Monochoria vaginalis. Interaction of nitrogen levels and weeding methods had significant response on yield and yield components of hybrid rice. The highest (7.61 t ha-1) grain yield was obtained from the combination @ 180 kg N ha-1 with weed free treatments. Comparable higher grain yield was obtained from the combination of pre emergence herbicide of bensulfuranm methyl + acetachlor) + one hand weeding with 180 kg N ha (7.48 t ha-1) and the combination of pre + post-emergence herbicide (Bispyribac sodium 18% + Bensulfuran methyl 12%) with 180 kg N ha-1 (7.56t ha-1). The estimated optimum dose of nitrogen for Pre EH, Post EH and 3HW (weed free) were 173, 189.1 and 189.4 kg N ha-1 respectively for BRRI hybrid dhan3 under AWD irrigation system.Bangladesh Agron. J. 2017, 20(1): 13-24

Essential Oils Constituents of Aerial Parts of Cyperus capitatus L. and Cyperus difformis L. Grown Wild in Egypt

This study aims to identify the chemical composition of the essential oils (EOs) of the aerial parts of two wild Egyptian Cyperus plants. Eos of aerial parts of Cyperus capitatus L. and Cyperus difformis L were extracted by hydrodistillation and analyzed by GC-MS. Forty volatile compounds were identified from both C. capitatus and C. difformis representing (90.67% and 91.52%) from the total mass, respectively. Terpenes were the major Eos constituents by ratios of 79.34% and 78.93% respectively. Sesquiterpenoids (oxygenated and non-oxygenated) represented (58.34% and 61.27%) of the total terpenes, While, monoterpenoids represented (21% and 17.66%) in both plants. Cyprene is the major compound (42.93% and 44.31%), followed by cyperotundone (10.66% and 11.57%) in both plants.

Effect of Water Regime and Weed Control Treatments on Weeds, Growth and Yields in Hybrid Rice

Two field experiments were conducted at Rice Research and TrainingCenter, Sakha, Kafr El-Sheikh, Egypt during 2015 and 2016 seasons to detect the effect of water regime and weed control treatments on weeds, growth and yields of hybrid rice (Sk2034H). Water regime (4-days on and 6-days off, saturation and continuous flooding) were allocated in main plots while weed control treatments were Thiobencarb 50% EC at three rates; 1.8 , 2.4 and 3.6 kg ai ha-1 in addition to weedy check were distributed in sub-plots. Weed species and hybrid rice yields were greatly influenced by water regime and weed control treatments. Echinochloa crus-galli and total weeds dry weights were significantly reduced under flooded or saturated plots than under shortage of water (4-days on + 6-days off). In different response, Cyperus difformis considerably reduced under the water shortage than saturated or flooded plots. The highest values of panicles per hill and grain yield of hybrid rice were recorded under flooding conditions followed by saturated soil. The application of Thiobencarb 50% EC at the high rate (3.6 kg ai h-1) resulted in the best weed control and highest grain yield followed by the application of 2.4 kg ai ha-1 from the same compound, while weedy check plots recorded the highest in weed presence and the lowest in rice yields. For the interaction, the lowest dry weights of Echinochloa crus-galli, Cyperus difformis and total weeds, also the largest weed control efficiency (%), number of panicles per hill and the highest rice grain yields were obtained under flooded plots treated with Thiobencarb at both rates of 2.4 and 3.6 kg ai ha-1. This trend was true under all treatments even the weedy check plots except for Cyperus difformis which increased significantly by soil saturation or flooding in un-treated plots.

Interference of allelopathic rice with paddy weeds at the root level

Despite increasing knowledge of the involvement of allelopathy in negative interactions among plants, relatively little is known about its action at the root level. This study aims to enhance understanding of interactions of roots between a crop and associated weeds via allelopathy. Based on a series of experiments with window rhizoboxes and root segregation methods, we examined root placement patterns and root interactions between allelopathic rice and major paddy weeds Cyperus difformis, Echinochloa crus-galli, Eclipta prostrata, Leptochloa chinensis and Oryza sativa (weedy rice). Allelopathic rice inhibited growth of paddy weed roots more than shoots regardless of species. Furthermore, allelopathic rice significantly reduced total root length, total root area, maximum root width and maximum root depth of paddy weeds, while the weeds adjusted horizontal and vertical placement of their roots in response to the presence of allelopathic rice. With the exception of O.sativa (weedy rice), root growth of weeds avoided expanding towards allelopathic rice. Compared with root contact, root segregation significantly increased inhibition of E.crus-galli, E.prostrata and L.chinensis through an increase in rice allelochemicals. In particular, their root exudates induced production of rice allelochemicals. However, similar results were not observed in C.difformis and O.sativa (weedy rice) with either root segregation or root exudate application. The results demonstrate that allelopathic rice interferes with paddy weeds by altering root placement patterns and root interactions. This is the first case of a root behavioural strategy in crop-weed allelopathic interaction.

Comparison of Weed Seedbanks in Different Rice Planting Systems

Core Ideas Weed seedbanks were compared in three rice planting systems: machine‐transplanted rice, water direct‐seeded rice, and dry direct‐seeded rice. Weed seedbanks were mainly distributed in soil within a depth of 10 cm. Dry direct‐seeded rice tended to maintain larger seedbanks of sedges, grasses, and some upland weeds. Water direct‐seeded rice contained the smallest weed seedbank overall. Machine‐transplanted rice had larger seedbanks of broadleaf weeds and some traditional rice weeds. Machine‐transplanted rice (Oryza sativa L.) (MTR), water direct‐seeded rice (WDSR), and dry direct‐seeded rice (DDSR) are three important alternatives to traditional manual transplantation of rice. Weed infestation is a pervasive problem in all rice planting systems. The weed seedbanks under different rice planting systems have seldom been compared. Thus, we sampled weed seeds in fields employing MTR, WDSR, and DDSR consecutively for at least 5 yr in Wujin County, eastern China. Seeds of 26 companion weed species of rice, comprising 16 families, were observed. Most weed seeds, 82.5% in MTR, 75.3% in WDSR, and 81.7% in DDSR, were distributed in soil 0‐ to 10‐cm deep. As soil depth increased, the seedbanks of total weeds, broadleaf weeds, grasses, and sedges all significantly decreased under the different rice planting systems, except for sedges under WDSR. The DDSR tended to maintain larger seedbanks of sedges and grasses, as well as some upland weeds, such as Digitaria sanguinalis (L.) Scop. and Eleusine indica Gaertn. The WDSR system contained the smallest weed seedbank overall but tended to have larger seedbanks of several weeds, such as Ammannia arenaria H. B. K. and Lindernia procumbens (Krock.) Philcox. Weedy rice and Cyperus difformis L. tended to maintain larger seedbanks in DSR fields. The MTR fields tended to have larger seedbanks of broadleaf weeds and some traditional rice weeds, with significantly lower richness of weed species in the seedbank. Therefore, to downsize the weed seedbank, WDSR or MTR should be employed rather than DDSR when possible. Moreover, the influences rotation of different rice planting systems on the weed seedbank merit more studies.

Impact of different herbicides on transplanted basmati rice in a Typic Haplustept soil of Punjab, India

A field experiment was conducted to evaluate the impact off different herbicides on transplanted basmati rice in Typic Haplustept soils of Punjab during kharif season of 2015–16. The predominant weed species observed in experimental farm were Echinochloa crusgalli, Cynodon dactylon, Cyperus rotundus, Cyperus difformis and Eclipta alba. The results showed that the grasses were the predominant weed species followed by broadleaf weeds and sedges. Significantly lower weed density (7.3/m2) and weed dry weight/m2 (5.4 g) were recorded in hand weeded plot which remained at par with pre-emergence herbicide bensulfuron methyl @ 55 g a. i./ha. The highest weed control efficiency (97%) was obtained with hand weeding followed by bispyribac sodium 10 SC @ 30 g a. i./ha (93.8%). The maximum plant height (143.9cm), number of tillers per plant (34.6), number of panicles per plant (48.3), number of filled grains per panicle (114.3), 1000-grain weight (32 g), grain yield (5964 kg/ha), straw yield (6327 kg/ha) and harvest index (20.4%) were recorded in HW plots followed by bensulfuron methyl @ 55 g a. i./ha with plant height (114.9 cm), number of tillers/plant (32.6), number of panicles/plant (46), number of filled grains per panicle (103.6), 1000-grain weight (29.2 g), grain yield (5714 kg/ha), straw yield (6280 kg/ha) and harvest index (18.4%).

Integrated weed management in direct-seeded rice

A field investigation was conducted during Kharif season of 2014 and 2015 at Varanasi, Uttar Pradesh, to study the effect of integrated weed management on weed flora, yield and economics of direct seeded rice (Oryza sativa L.). Penoxsulam 35 g/ha at 10 DAS fb 1 hand weeding at 35 DAS reduced weed density of various weed flora, viz. Echinocloa colona (7.27%), Echinocloa crus-galli (6.58%), Cynodon dactylon (7.57%) among grasses; Cyperus iria (8.01%), Cyperus difformis (8.26%) and Fimbristylis miliacea (8.67%) among sedges and Ammannia baccifera (10.12%) and Caesulia axillaris (10.10%) among broad-leaved weeds besides other weeds (11.72%) in comparison to penoxsulam 35 g/ha at 20 DAS fb 1 hand weeding at 35 DAS. Penoxsulam 35 g/ha at 10 DAS fb 1 hand weeding at 35 DAS markedly improved growth attributes, viz. plant height, number of tillers/m2, dry matter accumulation, leaf area index and chlorophyll content at 60 DAS and yield attributes, viz. panicle length, panicle weight, number of panicles/m2, number of grains/panicle and test weight. Penoxsulam 35 g/ha at 10 DAS fb 1 hand weeding at 35 DAS statistically influenced the grain and straw yields and harvest index over all other treatments except hand weeding at 15 and 35 DAS. Highest net return (43790.76) and benefit: cost ratio (2.15) was also observed under penoxsulam 35 g/ha at 10 DAS fb1 HW at 35 DAS.

Effect Of Vichete 5g And Rifit 500 Ec On The Occurrence And Phytosociological Attributes Of Weeds In Rice Field

Two herbicides namely Vichete 5G (12.5, 25.0, 50.0 kg/ha) and Rifit 500 EC (0.5, 1.0 L/ ha) were applied in BRRI Dhan 28 in the field to follow their effects on the occurrence and phytosociological attributes of weeds. A total of 29 weed species belonging to 22 genera covering 10 families was found to occur. 28 weed species under 21 genera and 9 families, 16 weed species under 14 genera and 6 families and 26 weed species under 21 genera and 10 families were assessed during 1st, 2nd and 3rd weedings respectively. 12 Species ( Eragrostis unioloides, Marsilea quadrifolia, Cyperus tenuispica, Murdania nudiflora, Fimbristylis miliacea, Rotala densiflora, Cyperus iria, Setaria pumilla, Fimbristylis diphylla, Leptochloe chinensis, Monochoria hastata and Oryza rufipogon) were recorded in first weeding but not found in second weeding. Cyperus rotundus, Panicum paludosum, Cyperus difformis, Marsilea quadrifolia and Echinocholoa crussgalli were found to be present at control only. They were controlled by the use of both herbicides. However, the number of weed species was found to reduce in the 2nd weeding in comparison to 1st one in all the treatments. Between the two weedicides, 50.0 kg/ha of Vichete 5G was relatively better than other doses of Vichete 5G and Rifit 500 EC and more effective to control weed species in 1st and 2nd weedings. In first weeding phytosociological attributes were highest in Schoenoplectus erectus and lowest in Rotala densiflora . In second weeding phytosociological attributes were highest in Eleocharis congesta and lowest in Panicum paludosum and Lindernia hyssopiodes while phytosociological attributes were highest in Fimbristylis miliacea and lowest in Marsilea quadrifolia of third weeding.
 Asiat. Soc. Bangladesh, Sci. 42(2): 129-144, December 2016

Weed Community Dynamics and System Productivity in Alternative Irrigation Systems in California Rice

Over the last 10 yr, California has experienced a series of ever-worsening droughts. Rice, traditionally a flooded crop, has come under increasing scrutiny with respect to its water use, leading to proposals to evaluate alternative irrigation systems. For growers, weed competition is one of the most limiting factors to maintaining high yields, so understanding the shifts among species in weed communities under the proposed alternative irrigation systems is vital. A field study was conducted from 2012 to 2014 to compare weed population and growth dynamics with three irrigation systems: (1) a conventional water-seeded control system (WS-Control), with a permanent flood of 10 to 15 cm from planting until 1 mo prior to harvest; (2) a water-seeded alternate wet and dry system (WS-AWD), with the field flooded from planting until canopy closure, after which floodwater was allowed to subside and the field was reflooded when the soil volumetric water content reached 35%; and (3) a drill-seeded alternate wet and dry system (DS-AWD), with rice drill seeded and then flush irrigated to establish the crop, after which the field was flooded until canopy closure and then underwent an alternate wet and dry (AWD) treatment similar to WS-AWD. In the AWD treatments, there were two drying periods, neither of which occurred after the heading stage. The dynamics of major weed species were evaluated using plant density counts (2012) and relative cover and biomass (2013 and 2014). Grasses (sprangletop and watergrass species) dominated the DS-AWD system; sedges, broadleaves, and grasses dominated both WS systems. The WS-AWD system increased smallflower umbrella sedge relative cover at canopy closure, relative dry weight at harvest, and percent frequency when compared with the WS-Control system. Yields did not differ across treatments when weeds were controlled (P>0.05); in the absence of herbicides, yields in the WS-AWD were equivalent to the WS-Control (ranging from 40 to 65% of the herbicide-treated yields) and zero in the DS-AWD due to weed pressure.

Residual effects of cultivation methods on weed seed banks and weeds in Cambodia

The effects of the planting method (transplanting vs. direct seeding), rice cultivar (Sen Pidao vs. Phka Rumduol), and herbicide application (admixture of bentazone and cyhalofop‐butyl) on weeds and weed seed banks were quantified in unflooded, shallowly flooded, and deeply flooded paddy fields in Cambodia in 2005 and 2006. Broad‐leaved weeds infested more toward maturity in 2006 than in 2005, particularly in directly seeded plots. Weed dry weights at pre‐heading and/or maturity were consistently reduced by herbicide application and Phka Rumduol cultivar, while weed numbers increased under unflooded condition. The proportion of sedges was consistently larger in directly seeded and non‐herbicide plots at pre‐heading. Larger numbers and dry weights of sedges and total weeds in 2005 caused larger seed bank sizes of sedges and total weeds in 2006, which further caused their infestation in 2006. A greater weed dry weight at 62 days after sowing in 2005 resulted in larger seed banks of Cyperus iria and Fimbristylis miliacea, which were most severe under non‐herbicide, direct‐seeded treatment, while that at rice maturity resulted in larger seed banks of Cyperus difformis, Scirpus juncoides, and Lindernia antipoda. Overall, sedges shared the majority of the total weed seed bank, followed by broad‐leaved weeds and then grasses. A lower yield in 2005 led to significantly larger seed bank sizes of sedges, but not of grasses or broad‐leaved weeds. Rice yield reduction was consistently related to larger numbers of sedges by heading and those of grasses at maturity.

A high-throughput, modified ALS activity assay for Cyperus difformis and Schoenoplectus mucronatus seedlings

Cyperus difformis L. (CYPDI) and Schoenoplectus mucronatus (L.) Palla (SCHMU) are major weeds of California (CA) rice, where resistance to acetolactate synthase (ALS)-inhibitors was identified in several CYPDI and SCHMU populations that have also evolved resistance to photosystem II (PSII)-inhibiting herbicides. The mechanism of ALS resistance in these populations remains to be clarified but this information is crucial in a weed management program, especially in a scenario where resistance to multiple herbicides has been identified. ALS activity assays are commonly used to diagnose resistance to ALS-inhibitors, but protocols currently available are burdensome for the study of CYPDI and SCHMU, as they require large amounts of plant material from young seedlings and have low yields. Our objective was to investigate the ALS resistance mechanism in suspected ALS-resistant (R) CYPDI and SCHMU biotypes using a modified ALS activity assay that requires less plant material. ALS enzymes from suspected R biotypes were at least 10,000-fold less sensitive to bensulfuron-methyl than susceptible (S) cohorts, indicating ALS resistance that is likely due to an altered target-site. Protein concentration (mgg−1 tissue) did not differ between R and S biotypes within each species, suggesting that R biotypes do not over produce ALS enzymes. CYPDI biotypes had up to 4-fold more protein per mg of tissue than SCHMU biotypes, but up to 7-fold more acetoin per mg−1 protein was quantified in SCHMU, suggesting greater ALS catalytic ability in SCHMU biotypes, regardless of their herbicide resistance status. Our optimized protocol to measure ALS activity allowed for up to a 3-fold increase in the number of assays performed per g of leaf tissue. The modified assay may be useful for measuring ALS activity in other weed species that also produce small amount of foliage in early growth stages when protein in tissue is most abundant.