Editorial |
Page No: 1-16
Seeing Weeds with New Eyes’ Part II– Some Historical
Perspectives and ‘Proto Weeds
Nimal R. Chandrasena
KEYWORDS:
ohalo-ii
ralp waldo emerson
proto-weeds
gerald mccarthy
william darlington
jethro tull
Abstract:
Continuing the theme ‘Seeing Weeds with New eyes’ (Chandrasena, 2019), in this issue of Weeds, I expand on some historical perspectives on matters related to colonizing taxa that have not received much attention within our discipline. My hope is that the emerging generation of weed scientists may benefit from deeper insights about the discipline’s history and how our attitudes towards weeds have changed and evolved with time. In the essay, I focus on the 18th century British inventor Jethro Tull (1674-1740); a medical doctor and amateur botanist from Penn State, USA - William Darlington (1782-1863); and a botanist from North Carolina, USA - Gerald McCarthy, whose contributions possibly shaped our discipline. I also provide a brief account of some recent archaeo-botanical findings from the Levant, that push the record of first-known weeds back 23,000 years, to a time well before settled agriculture. The findings from a site (Ohalo II) at the Sea of Galilee (Lake Kinneret, Israel) affirm that colonizing species were present well before some ancient humans settled in one place to do farming.
Email
nimal.chandrasena@gmail.com
Address
Current Address: Nature Consulting, 1, Kawana Court, Bella Vista, NSW 2153, Australia
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Perspective |
Page No: 17-29
Smooth Cordgrass (Spartina alterniflora Loisel.): The Case for Utilization of a Colonizing Plant Species
Gregory J. Duns
KEYWORDS:
Spartina alterniflora; cord grass; bioresources; biomass utilization; renewability; sustainability
Abstract:
The status of utilization of colonizing plants (weeds) must be regarded as being in infancy. With the
increasing need for alternative feedstocks to replace petroleum, which is used to produce energy, chemicals,
and other products, attention is now on alternative sources of biomass, such as agricultural and forestry
residues. However, weeds represent a considerable amount of biomass which remains a largely untapped
resource. Smooth cordgrass (Spartina alterniflora Loisel.) is an example of such a species that has yet to be
exploited to its full potential. This coastal, salt-tolerant plant has proliferated in many areas, especially in
China, forming extensive stands. The species was introduced to China from North America, about 40 years
ago, for coastal erosion protection. Since introduction, smooth cordgrass has colonized the coastal areas
forming extensive stands along China’s eastern seaboard. These infestations have become a severe
problem at many locations in the eastern coastal regions.
The present report is a case study and perspective concerning the utilization of smooth cordgrass in
China. I describe examples of the economical and efficient utilization of the plant’s biomass to form a variety
of practical products on a commercial scale. These show that it is possible to find new and effective ways to
achieve large-scale usage of otherwise waste biomass from this species and others, which are similar.
Further comprehensive research and development towards full valorization of smooth cordgrass with
innovative utilization are required. The future will hopefully see increasing utilization of weeds to meet the
increasing demand for resources that are sustainable and renewable.
Email
gjduns@gmail.com
Address
AirChem Consulting and Research, London, Ontario Canada N5X 0E2
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Perspective |
Page No: 30-34
Weed biology – A required foundation for effective weed management
Gulshan Mahajan and Bhagirath Singh Chauhan
KEYWORDS:
crop husbandry, harvest weed-seed tactics, seed ecology, weed phenology, seed bank, weed seed reproduction
Abstract:
Understanding of the biology of weeds (characteristics of seed production, seed dormancy, seedling emergence, plant growth, reproduction, and seed retention, as well as other physiological and morphological traits) is a prerequisite for the development of effective and sustainable weed management systems. Weeds are a persistent problem in agriculture, as they pose a direct threat to farmers’ profitability. Farmers currently rely heavily on herbicides for weed control; however, the development of herbicide-resistance and mechanisms of phenotypic, as well as genetic plasticity, in weeds amount to significant challenges in weed management. These are in addition to the underlying issue of environmental pollution as an outcome of excessive herbicide use. The results of weed biology studies are essential to reducing or eliminating the abundance of weeds and the development of herbicide-resistant weeds. Integrated weed management strategies, IWM (e.g. narrow row spacing, competitive cultivars, optimum sowing time and planting density, and harvest weed seed control) for effective weed control can be linked to currently available information on weed biology. The integration of management techniques based on biological knowledge of individual weeds could provide for sustainable weed control and the mitigation of herbicide resistance under both current and projected conditions.
Email
g.mahajan@uq.edu.au
Address
The Centre for Crop Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI) and School of Agriculture and Food Sciences (SAFS), The University of Queensland, Gatton, Queensland 4343, Australia
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Original Research |
Page No: 35-50
Weed control strategies for wheat (Triticum aestivum L.) in a cereal-legume cropping system on the Old Brahmaputra Floodplain, Bangladesh
Taslima Zahan, Md. Moshiur Rahman Mahfuza Begum, Md. Abdul Muktadir , Md. Zannatul Ferdous, Md. Enamul Haque and Richard W. Bell
KEYWORDS:
Herbicides; Productivity; Strip planted wheat; Weed management, Pendimethalin; Pretilachlor; Triasulfuron; Pyrazosulfuron-ethyl; Ethoxysulfuron; Carfentrazone-ethyl; Carfentrazone-ethyl plus isoproturon; 2,4-D amine
Abstract:
Strip planting is a promising establishment method for wheat (Triticum aestivum L.); however, wheat yields can sharply decline if weeds in the fields are not effectively managed. Therefore, to obtain an adequate and economically-viable weed control strategy for strip-planted wheat, we conducted a study, over two years (2013-14 and 2014-15) with commercially available herbicide. Our study was in Mymensingh, in the Eastern Gangetic Plains (EGP) in Bangladesh. In the study, we used pre-emergence (pendimethalin, pretilachlor and triasulfuron), early post- (ethoxysulfuron and pyrazosulfuron-ethyl) and late post-emergence (carfentrazone-ethyl, carfentrazone-ethyl plus isoproturon and 2,4-D amine) herbicides, following a sequential application approach. Sixteen treatment combinations with these herbicides were tested in wheat, and the trials included one ‘weedy check’ and one ‘weed-free check’. The study field was predominantly infested with three grass weeds [Cynodon dactylon (L.) Pers., Digitaria sanguinalis (L.) Scop. and Echinochloa colona (L.) Link], one sedge (Cyperus rotundus L.) and five broadleaf weeds [Polygonum lapathifolium L., Physalis heterophylla (L.) Nees, Lepidium didymum (L.), Chenopodium album L. and Vicia sativa L.]. Another broadleaf weed species - ragweed (Senecio vulgaris L.) - was also in the field as a minor weed. Polygonum lapathifolium was the most dominant weed species in both years. All herbicide treatments fully controlled this species during both years, except the treatments - pretilachlor followed by (fb) hand weeding at 25 days after sowing fb pretilachlor and pretilachlor fb 2,4-D amine. The herbicide treatments reduced the total weed biomass of strip-planted wheat by 66-95% in the first year and 71-100% in the second year. With regard to the weed control efficacy, six herbicide treatments: (1) pendimethalin followed by (fb) carfentrazone-ethyl plus isoproturon; (2) pendimethalin fb ethoxysulfuron fb carfentrazone-ethyl; (3) pendimethalin fb pyrazosulfuron-ethyl fb 2,4-D amine; (4) pretilachlor fb pyrazosulfuron-ethyl fb 2,4-D amine; (5) pendimethalin fb carfentrazone-ethyl; and (6) pretilachlor fb ethoxysulfuron fb carfentrazone-ethyl were the best performing combinations. These treatments provided more grain yield than the ‘weed-free check’ by 2-19% with the economic returns increasing by 30 to 164%. Additionally, bioassay testing of the soil in the treated fields indicated that the succeeding mungbean crop was not adversely affected by the residues of herbicides applied in the previous strip-planted wheat. Overall, the study suggests that the sequential application of pendimethalin followed by carfentrazone-ethyl plus isoproturon, pendimethalin/ pretilachlor followed by ethoxysulfuron with 2,4-D amine or pendimethalin/ pretilachlor followed by pyrazosulfuron-ethyl followed by carfentrazone-ethyl would be the most effective combinations for highly effective weed control in strip-planted wheat in the EGP. Given that the wheat fields are usually rotated with rice (Oryza sativa) and mungbeans (Vigna radiata), we contend that year-wise rotational application of those herbicide treatments in strip-planted wheat might minimize the risk of herbicide resistant weed development in those crop rotations as well as in the cropping pattern.
Email
taslimazahan_tzp@yahoo.com
Address
Bangladesh Agricultural Research Institute, Gazipur-1701, Bangladesh
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Original Research |
Page No: 51-69
Management of a herbicide-resistant ryegrass (Lolium rigidum) population in a crop rotation using alternative herbicides, row spacing, strategic nitrogen application and RR® canola (Brassica napus)
Abul Hashem, Wendy Vance, Ross Brennan and Richard W. Bell
KEYWORDS:
Herbicides; crop rotation, Lolium rigidum, resistant rigid ryegrass, urea ammonium nitrate (Flexi N), Roundup Ready® (RR®) canola, trifluralin, simazine, dimethenamid-p, pyroxasulfone
Abstract:
Rigid ryegrass (Lolium rigidum Gaud., henceforth, called ryegrass) is the most significant herbicideresistant weed in Australian grain cropping. Failure to adequately control ryegrass causes grain yield losses of about 36%. Therefore, new approaches for the control of ryegrass are needed in diverse crop rotations. We studied the options for managing a high-density Acetyl CoA Carboxylase (ACCase)-resistant ryegrass population in a lupin (Lupinus angustifolius L.) - wheat (Triticum aestivum L.) - canola (Brassica napus L.) rotation, under dryland conditions, at Cunderdin (31.650908 o S, 117.238906 o E), Western Australia (WA). Field trials were conducted during 2012 to 2014. In the 2012 lupin, and 2013 wheat crops, conventional herbicides (simazine in lupin, and trifluralin in wheat) and an alternative herbicide (dimethenamid-p in lupin, and pyroxasulfone in wheat) were tested. In 2014, Roundup Ready® (RR®) canola received two applications of glyphosate to control ryegrass. Three treatments of nitrogen (N) ((N1) 25 kg N ha-1 as urea; (N2) 50 kg N ha-1 as urea; and (N3) 50 kg N ha-1 as urea ammonium nitrate (UAN)) were applied to the 2013 wheat, and the 2014 RR® canola. Each crop was grown at two row spacings (22 cm, or 44 cm). None of the management factors except the herbicides significantly decreased the ryegrass density. Indeed, N3 (UAN) increased the emergence of ryegrass (more in 44 cm than 22 cm rows) compared to N1 and N2. Compared to urea N1, N3 reduced canola establishment by 28% and generally increased the grain yield of RR® canola by 11% but increased the density of ryegrass rather than controlling it. Dimethenamid-p, the alternative herbicide, decreased the ryegrass density in lupin and increased grain yield of lupin by 53%. While pyroxasulfone, the alternative herbicide, had no significant effect on the ryegrass density compared, to trifluralin in wheat, it increased the wheat grain yield by 25%. However, the 99% reduction in ryegrass by two applications of glyphosate in RR® canola was by far the most effective weed control. The inclusion of RR® canola technology in the rotation was the most effective approach to control the ACCaseresistant ryegrass, under dryland conditions of Western Australia.a
Email
hashemam@amnet.net.au
Address
Department of Primary Industries and Regional Development, Government of Western Australia, Northam, Australia
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