Floristic and Phytosociology of Weeds in Upland Rice in the Humid Tropics

ABSTRACT: Knowledge of the floristic composition and vegetation structure are essential conditions for development of more efficient and economic weed management strategies in crops in the humid tropics. The objective of the research was to carry on floristic and phytosociological surveys to know the main weeds in upland rice fields in the humid tropics of the Brazilian State of Maranhão. Weed samples were done by means of an open metal rectangle of 0.15 m2 thrown at random in the vegetative and reproductive stages of rice crop in 2009/10 and 2010/2011 harvest. A total of 65 species from 23 families was identified 35 (53.85%) from the eudicotyledons botanical group, 29 (44.06%) from the monocotyledonous and one (1.53%) belonged to the pteridophytes. The most representative families were from the monocotyledonous botanical group including Poaceae and Cyperaceae, followed by Amaranthaceae and Malvaceae, both from the eudicotyledons group. The weed species with higher importance values in the upland rice crop vegetative stage were Urochloasp., Panicumsp., C. flavus, C. benghalensis and C. argutus whereas in the reproductive stage the higher importance values were recorded for S. latifolia, C. argutus, L. octovalvis, A.tenella and P.maximum. The most important weeds in the crop vegetative phase were mainly from the monocotyledonous group, while in reproductive one they were the eudicotyledons. Weed diversity was high and the floristic similarity was lower in the vegetative one compared to the reproductive stage of upland rice cultivation in the humid tropics.

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Interactions of Nitrogen Source and Rate and Weed Removal Timing Relative to Nitrogen Content in Corn and Weeds and Corn Grain Yield

International Scholarly Research Notices ◽

10.1155/2017/8961367 ◽

2017 ◽

Vol 2017 ◽

pp. 1-8 ◽

Cited By ~ 2

Author(s):

Alexandra M. Knight ◽

Wesley J. Everman ◽

David L. Jordan ◽

Ronnie W. Heiniger ◽

T. Jot Smyth

Keyword(s):

Grain Yield ◽

Weed Management ◽

Management Strategies ◽

Field Studies ◽

Weed Species ◽

Weed Interference ◽

Coated Urea ◽

N Fertility ◽

Corn Grain ◽

Corn Grain Yield

Adequate fertility combined with effective weed management is important in maximizing corn (Zea mays L.) grain yield. Corn uptake of nitrogen (N) is dependent upon many factors including weed species and density and the rate and formulation of applied N fertilizer. Understanding interactions among corn, applied N, and weeds is important in developing management strategies. Field studies were conducted in North Carolina to compare corn and weed responses to urea ammonium nitrate (UAN), sulfur-coated urea (SCU), and composted poultry litter (CPL) when a mixture of Palmer amaranth (Amaranthus palmeri S. Wats.) and large crabgrass (Digitaria sanguinalis L.) was removed with herbicides at heights of 8 or 16 cm. These respective removal timings corresponded with 22 and 28 days after corn planting or V2 and V3 stages of growth, respectively. Differences in N content in above-ground biomass of corn were noted early in the season due to weed interference but did not translate into differences in corn grain yield. Interactions of N source and N rate were noted for corn grain yield but these factors did not interact with timing of weed control. These results underscore that timely implementation of control tactics regardless of N fertility management is important to protect corn grain yield.

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Model of rice (Oryza sativa) yield reduction as a function of weed interference

Weed Science ◽

10.1017/s0043174500092742 ◽

1997 ◽

Vol 45 (2) ◽

pp. 218-224 ◽

Cited By ~ 21

Author(s):

Karl W. VanDevender ◽

Thomas A. Costello ◽

Roy J. Smith

Keyword(s):

Weed Management ◽

Management Strategies ◽

Economic Assessment ◽

Richards Equation ◽

Yield Reduction ◽

Published Data ◽

Weed Species ◽

Individual Parameter ◽

Alternative Weed Control ◽

Parameter Values

Economic assessment of weed management strategies in rice is dependent upon a quantitative estimate of the yield impact of a given weed population. To assist rice producers in making such assessments, a mathematical model was developed to predict rice yield reduction as a function of weed density and duration of interference. The nonlinear empirical model was a unique 3-dimensional adaptation of the Richards equation with 4 parameters. Using published data, individual parameter values were fitted for each of 6 weed species interfering with either conventional or semi-dwarf statured rice cultivars. The functional form of the equation produced surfaces that were qualitatively consistent with available data and experience regarding rice-weed biology. Hence, predictions from the model should be useful and reliable in assessing the economic impact of weeds and in determining the feasibility of alternative weed control treatments for various field scenarios.

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Weeds and Their Effect on the Performance of Maize and Finger Millet in Mid-Hills of Nepal

International Journal of Applied Sciences and Biotechnology ◽

10.3126/ijasbt.v2i3.10790 ◽

2014 ◽

Vol 2 (3) ◽

pp. 275-278 ◽

Cited By ~ 1

Author(s):

Tika Bahadur Karki ◽

Shrawan K. Sah ◽

Resam B. Thapa ◽

Andrew J. McDonald ◽

Adam S. Davis ◽

...

Keyword(s):

Weed Management ◽

Crop Production ◽

Finger Millet ◽

Crop Yields ◽

Management Strategies ◽

Cropping System ◽

Weed Species ◽

Ageratum Conyzoides ◽

Alternative Crop ◽

Weed Infestation

Relay cropping of maize with fingermillet (maize/fingermillet) is the predominant cropping system for sustaining food security situation in the hilly regions of Nepal. In this region weed pressure severely reduces crop yields. Basic information on weed species composition, biomass production and their effect on crop yields and economics are lacking for this region. This information will be necessary to develop effective weed management strategies for the future. In light of this an empirical study was carried out in two representatives mid hill districts of Parbat and Baglung during summer season of 2010/2011 in Nepal. A total of 10 major weed species with densities of 172 in Parbat and 311 per 0.25m2 area in Baglung were observed. The highest percentage of both relative and absolute densities were recorded for Ageratum conyzoides in Parbat and Polygonum chinensis in Baglung. Weed infestation under farmers practice of crop management reduced the grain yield of maize by 1.985 Mt ha-1 (117%) in Baglung and 1.760 Mt ha-1 (108%) in Parbat. Similarly, in finger millet it was 0.489 Mt ha-1 (63%) in Baglung and 0.403 Mt ha-1 in Parbat. Similarly, the combined yield of both the crops was also significantly reduced by 79.3% and 61.7% in Baglung and Parbat respectively. Hence, weeds are directly affecting the crop performance in the region. Therefore, there is an urgent need to develop an alternative crop production system in the hills. DOI: http://dx.doi.org/10.3126/ijasbt.v2i3.10790Int J Appl Sci Biotechnol, Vol. 2(3): 275-278

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Smoke-Isolated Trimethylbutenolide Inhibits Seed Germination of Different Weed Species by Reducing Amylase Activity

Weed Science ◽

10.1614/ws-d-14-00068.1 ◽

2015 ◽

Vol 63 (1) ◽

pp. 312-320 ◽

Cited By ~ 6

Author(s):

Heino B. Papenfus ◽

Manoj G. Kulkarni ◽

Martin Pošta ◽

Jeffrey F. Finnie ◽

Johannes Van Staden

Keyword(s):

Seed Germination ◽

Weed Management ◽

Amylase Activity ◽

Management Strategies ◽

Biologically Active ◽

Weed Species ◽

Water Control ◽

Weed Seeds ◽

Dark Conditions ◽

Smoke Water

Weeds pose a great problem to farmers worldwide, and controlling weeds demands a high input cost for herbicides and labor. Because of current environmental regulations, a limited number of herbicides are commercially available (with limited modes of action) to control weeds. Smoke water and the biologically active compounds isolated from smoke affect seed germination in a significant way. Smoke water (SW) and karrikinolide (KAR1, the germination stimulant isolated from smoke) have been tested extensively for their ability to promote seed germination in a vast array of plant species. In addition to KAR1, a germination inhibitor, trimethylbutenolide (TMB), was also isolated from plant-derived smoke. The effects of SW, KAR1, and TMB were tested on five major weed species of South Africa: fleabane, hairy wild lettuce, bugweed, spilanthes, and fameflower. Seeds of these weed species were subjected to 16/8 h light/dark conditions or to constant dark conditions at constant temperatures of 20, 25, 30 C and alternating 30/20 C. SW and KAR1significantly increased germination, whereas TMB significantly inhibited germination of these weed species. Furthermore, TMB treatment reduced the amylase activity of the tested weed seeds compared with the water control. These results indicate the possibility of manipulating germination of certain weed seeds by SW, KAR1, and TMB. Thus, smoke and smoke-isolated compounds could potentially be used in new weed management strategies.

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Weed Management Strategies in Chickpea (Cicer arietinum): A Review

Agricultural Reviews ◽

10.18805/ag.r-1996 ◽

2020 ◽

Author(s):

Akashdeep Singh ◽

S. S. Rana ◽

Anju Bala

Keyword(s):

Weed Control ◽

Cicer Arietinum ◽

Weed Management ◽

Management Practices ◽

Management Strategies ◽

Detailed Knowledge ◽

Basic Requirement ◽

Weed Species ◽

The World ◽

Hand Weeding

Chickpea (Cicer arietinum) is one of the most important pulse crops but it’s productivity in India is quite low. There are various reasons for low productivity. Weed control is the basic requirement and the major component of crop management. Weeds on an average reduce the crop yield by 40-87 per cent. Deciding time to control weeds requires detailed knowledge of the weed populations in the field. Different management practices like altering spacing, competitive cultivars, etc. can help in enhancing the productivity. With the world entering the precision-farming era, more emphasis is being put on the use of post-emergence herbicides. Application of two or more herbicide at the same time or as a double knockdown and integrating with hand-weeding provides desirable control of different weed species besides reducing the hazard of chemical weed control.

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Glyphosate Applied at the Early Reproductive Stage Impairs Seed Production of Glyphosate-Resistant Hairy Fleabane

Planta Daninha ◽

10.1590/s0100-83582019370100104 ◽

2019 ◽

Vol 37 ◽

Author(s):

C. PIASECKI ◽

A.S. MAZON ◽

A. MONGE ◽

J.A. CAVALCANTE ◽

D. AGOSTINETTO ◽

...

Keyword(s):

Seed Production ◽

Seed Bank ◽

Integrated Management ◽

Management Strategies ◽

Production Capacity ◽

Reproductive Stage ◽

Weed Species ◽

Conyza Bonariensis ◽

Seed Analysis ◽

Hairy Fleabane

ABSTRACT: Glyphosate-resistant hairy fleabane [Conyza bonariensis (L.) Cronq.] is one of the most important weeds in the world. Among the factors that make this weed species widely distributed in the most diverse environments is the high seed production capacity and dispersal. Hairy fleabane plants not controlled by herbicide application regrowth and overcome crop canopy, use environmental resources, interfere with crops, and complete their life cycle by producing thousands of seeds and replenishing the seed bank. Management strategies that reduce production and viability of hairy fleabane seeds can be adopted within the integrated management to reduce the seed bank and prevent further infestations. In this way, experiments were carried out in a greenhouse and laboratory of seed analysis to evaluate the effect of glyphosate (1,480 g a.e. ha-1) on the production and viability of glyphosate-resistant hairy fleabane seeds when applied at the vegetative and reproductive stages. Seed production was reduced by 68.4 and 100% when glyphosate was applied on hairy fleabane plants at the vegetative and early reproductive stages, respectively, regarding to the control. The viability of hairy fleabane seeds was not influenced by treatments at the evaluated stages. However, glyphosate treatment reduced the hairy fleabane seed production when applied at the vegetative stage . Hairy fleabane seed production is not feasible when glyphosate is applied at the early reproductive stage.

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Herbicide Rate Effects on Weed and Root Maggot Dynamics in Canola

Weed Science ◽

10.1614/ws-07-172.1 ◽

2008 ◽

Vol 56 (3) ◽

pp. 477-483 ◽

Cited By ~ 4

Author(s):

Jim S. Broatch ◽

Lloyd M. Dosdall ◽

John T. O'Donovan ◽

K Neil Harker ◽

George W. Clayton

Keyword(s):

Weed Management ◽

Management Practices ◽

Management Strategies ◽

Dry Weight ◽

Field Studies ◽

Crop Damage ◽

Weed Species ◽

Alternate Host ◽

Insect Management ◽

Root Maggot

Weed management strategies can influence insect infestations in field crops, yet no attempts have been made previously to manipulate weed populations in canola for integrated weed and insect management. Field studies were conducted during 2003 to 2005 at Lacombe and Beaverlodge, Alberta, Canada to manipulate weed and root maggot, Delia spp. (Diptera: Anthomyiidae), interactions in canola. Densities of monocot weeds were varied by altering herbicide applications, with rates ranging from 0 to 100% of the rate recommended. Weed populations declined, and yields were variable with increased herbicide rates. Root maggot damage decreased with increases in monocot weed dry weight for both canola species at both study sites. Results support the hypothesis that heterogenous environments, arising from mixed populations of monocot weeds with canola, minimize opportunities for females of Delia spp. to complete the behavioral sequence required for oviposition, leading to reduced infestation levels in weedy systems. However, effects of dicot weeds on root maggot infestations varied between sites as a result of site-related differences in weed species complexes. When wild mustard was common, crop damage increased, because this weed can serve as an alternate host for root maggots. The study emphasizes the importance of adopting crop management practices that are compatible for both weed and root maggot control.

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Effect of Crop Residue on Seedling Emergence and Growth of Selected Weed Species in a Sprinkler-Irrigated Zero-Till Dry-Seeded Rice System

Weed Science ◽

10.1614/ws-d-12-00147.1 ◽

2013 ◽

Vol 61 (3) ◽

pp. 403-409 ◽

Cited By ~ 15

Author(s):

Bhagirath S. Chauhan ◽

Seth B. Abugho

Keyword(s):

Field Study ◽

Weed Control ◽

Weed Management ◽

Crop Residue ◽

Crop Residues ◽

Seedling Emergence ◽

Management Strategies ◽

Weed Species ◽

Weed Biomass ◽

Residue Retention

Crop residues acting as mulches can influence weed seedling emergence and weed biomass. A field study was conducted to evaluate the effect of rice residue amounts (0, 3, and 6 t ha−1) on seedling emergence of eight weed species in zero-till dry-seeded rice. The highest seedling emergence of spiny amaranth, southern crabgrass, crowfootgrass, junglerice, eclipta, goosegrass, and Chinese sprangletop was observed in the absence of residue. Seedling emergence of these weeds declined with increasing residue amounts; however, the greatest and most substantial reductions in emergence occurred with 6 t ha−1of residue. The presence of residue also resulted in less weed biomass than with the no-residue treatment. The emergence and biomass of threelobe morningglory seedlings, however, were not influenced by residue amounts. The use of residue also increased the time taken to reach 50% of maximum emergence for some species, for example, spiny amaranth and Chinese sprangletop. The results of our study suggest that the use of residue at high rates can help suppress seedling emergence and growth of many weeds. However, there is a need to integrate other weed management strategies with residue retention to achieve season-long weed control.

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Weed diversity and weed management

Weed Science ◽

10.1017/s0043174500092985 ◽

1997 ◽

Vol 45 (3) ◽

pp. 357-363 ◽

Cited By ~ 58

Author(s):

Jack Dekker

Keyword(s):

Weed Management ◽

Phenotypic Diversity ◽

Management Strategies ◽

Physical Space ◽

Cropping System ◽

Weed Species ◽

Plant Parts ◽

Weed Diversity ◽

Diversity Enhancement

The story of agriculture is the story of weed interference. After millennia of weed control we still have weeds. This situation has led many growers to observe that “the weeds always win.” One of the most important reasons weeds are so successful is their biodiversity. Biodiversity is an inevitable consequence of the struggle an individual weed species undergoes in the presence of neighbors, and by occupying a physical space in an agroecosystem. Weeds have evolved in response to cropping system practices by adapting and occupying niches left available in agroecosystems. Forces created by our cropping practices over evolutionary time have led to the weed diversity we observe today. Diversity underlies weed management in several important ways. A plant experiences diversity among its neighbors in at least five different ways. Weeds have adapted to selection in agroecosystems in several ways: (1) genetic variants within a species; (2) somatic polymorphism of plant parts; (3) success in diverse habitat microsites; (4) temporal adaptations within the community; and (5) floristic diversity of a community at higher levels than the species. Herein, weed diversity is discussed in this broader context, in terms of population behaviors that emerge as a consequence of the activities of individual components at lower levels of organization. Diversity is also discussed in terms of its implications for weed management. The potential exists to develop management strategies based on differences in weed and crop diversity. These strategies might be developed by characterization of weedy genetic and phenotypic diversity; enhancement of crop, cropping system, and agroecosystem diversity; and characterization of the spatial distribution of weed populations.

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Evaluating Seed Shatter of Economically Important Weed Species

Weed Science ◽

10.1614/ws-d-16-00081.1 ◽

2016 ◽

Vol 64 (4) ◽

pp. 673-682 ◽

Cited By ~ 11

Author(s):

Nikki R. Burton ◽

Hugh J. Beckie ◽

Christian J. Willenborg ◽

Steven J. Shirtliffe ◽

Jeff J. Schoenau ◽

...

Keyword(s):

Weed Management ◽

Field Experiments ◽

Management Strategies ◽

Wild Oat ◽

Population Abundance ◽

Weed Seed ◽

Weed Species ◽

Wild Mustard ◽

Green Foxtail ◽

Crop Maturity

The increasing occurrence of herbicide resistance, along with no new herbicide modes of action developed in over 30 yr, have increased the need for nonherbicidal weed management strategies and tactics. Harvest weed seed control (HWSC) practices have been successfully adopted in Australia to manage problematic weeds. For HWSC to be effective, a high proportion of weed seeds must be retained on the plant at crop maturity. This 2-yr (2014, 2015) study evaluated seed shatter of wild oat, green foxtail, wild mustard, and cleavers in both an early (field pea) and late (spring wheat) maturity crop in field experiments at Scott, Saskatchewan. Seed shatter was assessed using shatter trays collected once a week during crop ripening stage, as well as at two crop maturation or harvest stages (swathing, direct-combining). Seed shatter differed among weed species, but was similar between crops at maturity: ca. 30% for wild oat, 5% for cleavers, < 2% for wild mustard, and < 1% for green foxtail. Overall, seed shatter of wild oat occurred sooner and at greater levels during the growing season compared with the other weed species. Viability of both shattered and plant-retained seeds was relatively high for all species. The small amount of seed shatter of cleavers, wild mustard, and green foxtail suggests that these species may be suitable candidates for HWSC. Due to the amount and timing of wild oat seed shatter, HWSC may not reduce population abundance of this grassy weed.

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