Weed Management Options Research Articles

From rice-like plants to plants liking rice: A review of research on weeds and their management in African rice systems

Competition from weeds is the most important yield reducing factor in African rice production systems. Generally important weed management practices in rice are controlled flooding and the use of herbicides. Smallholder rice farmers in Africa however often lack the necessary water management infrastructure, access to affordable, good quality herbicide products and knowledge and equipment for their safe and effective application. Against this challenging backdrop, effective and affordable weed management strategies are highly needed. The literature on weed ecology and management in African rice systems is systematically reviewed to assess achievements in the last quarter of the past 50 years of international rice research endeavours, the period since the last comprehensive review (2009), and to propose the way forward for research and development. Most published studies are from West Africa and focussed on rainfed upland (43% of all relevant studies) or rainfed lowland (32%) rice. Grasses are the most frequently studied weed types, closely followed by parasitic weeds and broadleaved weeds (ex aequo). Most research (75% of published studies) focussed on weed management, mostly referring to or including curative measures (e.g., chemical, manual) or preventive weed management options that improve weed competitiveness of the crop (e.g., crop establishment, cultivars), while less attention was observed for preventive measures aiming at reduced weed recruitment or seed bank sizes (e.g., crop rotations, intercropping, mulches) or integrated weed management approaches. Future research should invest more in developing integrated weed management strategies that achieve (1) reduced weed recruitment, (2) reduced weed seed bank sizes and (3) improved crop competitiveness and that are compatible with farmer's production resources, fairly independent of (agrochemical) industries and markets and benign to the environment and human health. We recommend research on parasitic weeds to focus on a further broadening of the range of currently available management options, with a particular focus on the role of soil fertility and more efficient fertiliser technologies that simultaneously improve crop productivity and quality. For research to contribute to the development of meaningful weed management strategies for African rice systems in the future, we believe it would be best to identify and focus on target-location specific weed-communities, and to reconcile field level weed management strategies with the preconditions set at higher system levels (e.g., farming and agricultural systems) and anticipated scenarios regarding changing demographics and biophysical and institutional environments.

Effect of Crop Establishment Methods and Weed Management Practices on Productivity and Profitability of Clusterbean under Semi-arid Region of Rajasthan

Background: Adequate tillage checks and delays the emergence of weeds and provides a more favourable environment for early crop establishment. Slow growth of crop plant provides favourable environment for emergence of weeds. Cultural as well as mechanical practices such as hand weeding and intercultural are effective but unavailability of labour and continuous rainfall in rainy season does not permit for timely management of weeds Chemical weed control is effective weed management option which provides effective control of weeds. It is well known that weeds are ubiquitous but their presence in cropped area particularly in rainy season crops like clusterbean act as major limiting factor in achieving high potential yield. The current study aimed to study the impact of crop establishment methods and weed control practices on productivity and profitability of clusterbean. Methods: A field experiment was carried out to find out suitable method of crop establishment methods and weed management practices in clusterbean during kharif seasons of 2018, 2019 and 2020. The experiment was conducted in spilt plot design with three replications. The treatments were four crop establishment methods viz., conventional sowing, zero tillage sowing, broad bed sowing, zero tillage sowing with mulch as main plots and four weed control practices viz., weedy check, pendimethalin+imazethapyr 1000 g ha-1, T3- Imazethapyr 40 g ha-1, T4-Imazethapyr+imazamox 40 g ha-1 as sub plot treatments . Result: The broad bed sowing of clusterbean along with pre-emergence application of pendimethalin+ imazethapyr 1000 g ha-1 was found effective to achieve higher productivity and farm profitability.

EVALUATING THE PHYTOTOXIC EFFECTS OF SOME PLANT SPECIES OF SEMI-ARID REGIONS

The most effective method for weed control is the use of herbicides. However, the scope of this method is narrowing down due to herbicide-resistant weeds and the non-availability of new chemistry herbicides. Hence, to explore natural weed management options, the herbicidal potential of three weed species extracts namely Opuntia ficus-indica, Murraya koenigii and Dryopteris felix-mas were evaluated in lab and wirehouse experiments. A completely randomized design with factorial arrangements was used for lab and completely randomized design was used for wirehouse experiments. Each experiment was repeated twice with four replications each time. Data pertaining to seed germination, seedling growth and physiological traits of crops and weeds were recorded using standard procedures. Data indicated that aqueous extracts of tested species depicted more phytotoxicity than N-hexane extracts against germination and seedling growth of lettuce in the lab experiment. Aqueous extract of Opuntia ficus-indica completely inhibited lettuce seed germination whereas, N-hexane extract of the same species has least effect on germination and germination traits like mean germination time, time taken to 50% germination, germination index. The aqueous extract of O. ficus-indica resulted in minimum lentil, mashbean, mungbean, parthenium and Trianthema portuclacastrum seedling leaf area, chlorophyll content, shoot, root length, dry weight and maximum electrolyte leakage. The foliar application of O. ficus-indica, M. koenigii and D. felix-mas water extracts on seedlings of lentil, mashbean, mungbean, parthenium and T. portuclacastrum followed the phyto-toxicity order O. ficus-indica aqueous extract ˃ D. felix-mas aqueous extract ˃ M. koenigii aqueous extract. The growth-inhibitory demonstrations of O. ficus-indica extract suggest that active substances with herbicidal properties are present in this plant which could be exploited as natural weedicide.

Weed Management in Oilseed Crops - A Review

Oilseed crops are slow growing during the initial growth period. In oilseeds, weeds caused yield reduction by 15-60 percent. Hence it is very essential to control weeds during the critical period of crop-weed competition. Weed management options in the majority of oilseed crops are limited, therefore, adoptions of multiple options of weed management using ‘little hammers’ considering preventive, cultural, mechanical, chemical, and biotechnological approaches are important. Integrated weed management (IWM) is a system approach to minimize weed populations below the economic threshold level. Among different weed management practices, cultural practices minimized the crop-weed competition up to large extent. Further, mechanical measures and herbicidal weed management are ‘large hammers’ or single large methods of weed control, but that may lead to the development of another level of problems like shift in weed flora, development of difficult-to-control weeds, issues of herbicide resistance, establishment of perennial weeds, etc. Thus, the aforesaid problems can be overcome by suitably adopting IWM, since it mixes the use of different available weed control methods in a balanced way by managing the weeds effectively, and sustainably provides higher production without harming the environment.

Nitrogen and weed management effects on weeds and yield of barley in Kandahar, Afghanistan

Growth and yield of barley (Hordeum vulgare L.) are highly influenced by nutrients and weed management. Nitrogen (N) is the most crucial nutrient to which barley crop responds readily. Efficient management of N and weeds can provide higher yield, better quality, and higher income to the farmers. Therefore, a field experiment was conducted in a split-plot design with three replications during winter season of 2019-20 in the Afghanistan National Agricultural Sciences and Technology University (ANASTU), Kandahar, Afghanistan to evaluate the effect of weed and N management on weeds growth and barley productivity. There were three weed management options in main plots, such as weedy check, herbicide use alone [post-emergence application (PoE) of clodinafop-propargyl 60 g/ha + metsulfuron-methyl 4 g/ha (tank-mix) at 30 days after sowing (DAS)], and integrated weed management (IWM) involving stale seed bed 15 days before sowing + wheat crop residue (2.5 t/ha) retention + clodinafop-propargyl + metsulfuron-methyl (tank-mix) PoE with half of the recommended dose at 30 DAS]. Four N levels (~0, 40, 80 and 120 kg N/ha, i.e., N0, N40, N80 and N120) were included as sub-plot treatments. The IWM led to significantly lower density and biomass of weeds at 40 and 70 DAS and significantly increased weed control efficiency (WCE) and weed control index (WCI). Clodinafop-propargyl (60 g/ ha) + metsulfuron-methyl (4 g/ha) (tank-mix) PoE also resulted in significantly lower density and biomass of weeds and higher WCE and WCI than weedy check at all stages. IWM being at par with clodinafop-propargyl + metsulfuron-methyl (tank-mix) PoE led to higher growth (crop height, dry weight, leaf area index and growth rate) and yield of barley. On the contrary, the effect of nitrogen levels was not significant on the weed density and biomass reduction. N120 and N80 were comparable with respect to growth, yield attributes and yield of barley. Thus, IWM with 80 kg N/ha may be recommended for better weed management and higher barley yield and income in Kandahar, Afghanistan.

Značaj suzbijanja korova i roka sjetve u proizvodnji kivana (Cucumis metuliferus E. Meyer Ex. Naudin) na području istočne Slavonije

Seed germination, growth, flowering and yields of kiwano (Cucumis metuliferus E. Meyer Ex. Naudin) were examined in eastern Slavonia during 2021 growing season. The objective of this study was to determine agro-morphological diversity within kiwano growing under different weed management practices and sowing time. The experiment was arranged as a 3 x 3 factorial design with three replications. Factors included three weed management options (wheat straw mulch, cultivation and un-weeded control) and three planting dates (early, mid and late May). A typical summer weed community that develops during experiment dominated with bristly foxtail (Setaria verticilata (L.) P. Beauv.) and redroot pigweed (Amaranthus retroflexus L.) while the others were with lower relative density and frequency per unit area and with the lower impact on the crop. Weed control was very effective compared to weedy check. However, sowing date appears as a critical factor in kiwano production, influencing not only emergence, growth and flowering, but also fruit number and size. This study concluded that mid sowing time and cultivation as a weed control measure has a highest agronomic potential for a kiwano production following by mid and early sowing time with mulch as a weed control measure.

Effect of planting geometry and potato seed tuber size on weeds and potato tuber yield

A field experiment was conducted during winter (Rabi) seasons of 2014-15 and 2015-16 at Punjab Agricultural University, Ludhiana, India to study the effect of potato planting geometry (50 × 15 cm, 65 × 11.5 cm, 70 × 10.7 cm and 75 × 10 cm) and seed tuber size (25-35 mm, 35-45 mm, 45-55 mm) on weed density and biomass, and tuber yield of potato. The potato canopy cover was higher and the weed density and biomass were lower with closer planting geometry of 50 × 15 cm followed by 65 × 11.5 cm. The growth attributes (number of stems/plant and leaf area index), tuber number and tuber yield were not significantly influenced by varying planting geometry. Potato seed tuber size exerted a significant effect on weed infestation resulting in significantly lower weed density and biomass with large sized seed tubers followed by medium sized seed tubers as compared to small sized seed tubers. Growth attributes, tuber number and tuber yield of potato were also significantly higher with large sized seed tubers followed by medium sized tubers compared to small sized tubers. Thus, the potato planting geometry of 50 × 15 cm for manual planting by small and marginal farmers and 65 × 15 cm for mechanized potato production along with medium sized seed tubers are the viable options for effective weed management and optimal potato tuber yield.

Application of Reduced Doses of Trifluralin and Non-Chemical Weed Management Options in Weed Management of Dill (Anethum Graveolens L.)

Application of Reduced Doses of Trifluralin and Non-Chemical Weed Management Options in Weed Management of Dill (Anethum Graveolens L.)

Managing Weeds In Dry Direct Seeded Rice: A Profound Challenge

Dry Direct Seeded Rice (DDSR) is a promising technology to address environmental, water, labor and profitability issue that is constantly threatening the rice farming community around the world. Rice yield under DDSR is primarily limited due to weeds. There are instances of complete crop failure in DDSR owing to poorly managed weeds. More than 50 weeds species infest DDSR crop due to aerobic nature of soil confronting a major challenge in the wide spread adoption of dry direct seeding. Direct-seeded rice faces a potential threat from changes in the competing weed flora, with an increase in those species that are difficult to control. This review article presents the prospects of DDSR along with the available weed management strategies such as preventive, physical, chemical, cultural and biological methods and their judicious use. Over reliance on only one approach of managing weeds may be back firing as well. The use of chemical means are getting popular in an alarming rate for being cost effective, without calculating the environmental concerns which might lead to herbicidal resistance and negative consequences to environment and human health. Therefore, it is necessary to understand the environment while shifting from transplanted rice to dry direct seeding, identifying weeds flora and choosing or integrating the best weed management practices foreseeing the future consequences. The logical integration of available weed management options that is ecologically sound, economic and effective for season long weed control is the main essence that ensures the sustainability of rice production.

Does Conservation Agriculture Work For Rainfed Farming In Nepal? A Review

Intensive tillage-based agricultural practices severely affect the soil’s physical, chemical and biological properties that eventually limit the crop yields in longer run. It is due to declining soil physical, chemical and biological properties. Several studies have been done to restore and improve the soil quality, however conservation agriculture (CA)-based practices of minimum tillage, crop residue retention and appropriate crop rotations has been observed to be promising across the globe. Studies on CA under Nepal’s rainfed farming systems of Terai and hills of Nepal improved the soil quality, increased individual crop and system yields, reduced labor demand and was economically profitable. However, lack of adequate soil moisture during planting in initial seasons, inadequate tillage equipment and weed management options are the key constraints of rainfed farming to be transformed into CA in initial stages. In Nepal, the introduction of animal-drawn direct seeding equipment, management of residues or mulches, mechanical or herbicidal weed management options for small-scale rainfed hill farmers can be of paramount significance in scaling-out of the CA based practices in Nepal. For this, further on-station and on-farm verifications of CA based practices need to be carried out across the various cropping systems and agro[1]ecological regions of the country by Nepal Agricultural Research Council (NARC), Nepal in collaboration with international CG centers, universities, extension and development institutions.

Bioefficacy, Phytotoxicity and Economics of Post-emergence Herbicides in Moth Bean (Vigna aconitifolia) in Hot Arid Regions

Background: Weed infestation is the major cause of yield loss to Kharif pulses in arid regions. Post-emergence herbicide application is a promising weed management option for pulses in these areas. Therefore, the current study was aimed to find an effective and economic post-emergence herbicide molecule for weed control in moth bean. Methods: A field experiment was conducted during 2017-2019 with different herbicides, hand weeding, weed-free and unweededs in Kharif mung bean in a randomized complete block design with three replications. Result: Among the herbicide treatments, post-emergence application of propaquizafop + imazethapyr @ 125 g a.i. ha-1 being statistically at par with clodinafop-propargyl + sodium acifluorfen @ 312.5 g a.i. ha-1 and hand weeding recorded the highest reduction in total weed dry matter (73.9%), highest weed control efficiency (73.8%) and lowest weed persistence index (1.03) compared to the unweeded. The reduction in seed yield in unweeded compared to weed-free and hand weeding was 50.8% and 42.1%, respectively. As the imazethapyr-containing herbicides caused crop phytotoxicity, significantly higher crop dry weight (513 g m-2), seed yield (5.53 q ha-1), stover yield (18.0 q ha-1), gross returns and net benefits of moth bean were recorded with clodinafop-propargyl + sodium acifluorfen (312.5 g a.i. ha-1) over other herbicide treatments. Clodinafop-propargyl + sodium acifluorfen (@312.5 g a.i. ha-1) registered the minimum value of weed index (20) and highest values of herbicide efficiency index (3.9) and crop resistance index (4.70).

Effect of Crop Establishment Methods and Weed Management Practices on Weed Density and Productivity of Basmati Rice (Oryza sativa L.)

Aim: Present experiment was conducted to study the effect of crop establishment methods and weed management options on weed dynamics and performance of Basmati rice.
 Study Design: Split plot design.
 Place and Duration of Study: Iinvestigation was conducted during the kharif-season of 2019 and 2020 at Crop Research Center, S.V.P.University of Agriculture &Technology, Meerut (U.P.), India.
 Methodology: Mainfactors consist of the crop establishment methodsviz.(1) Conventional Puddled Transplanting, (2) Unpuddled Flat and (3) Furrow Irrigated Raised Beds, the sub factors consist of five weed management options viz., (1) Pretilachlor @ 0.75 Kg ha-1 PE fb Bispyribac sodium @ 20 g a.i. ha-1 POE at 20 DAT, (2) Almix 4 g a.i. ha-1 + Bispyribac sodium @ 20 g a.i. ha-1 POE at 20 DAT, (3) Bispyribac sodium @ 25 g a.i. ha-1 POE at 20 DAT, (4) Two hand weedings and (5) Weedy check.
 Results: Minimum total weed density was recorded under CPT (E1) followed by FIRB(E3) while itwas maximum under UPF(E2). Two hand-weedings effectively reduced total weed density. In herbicides, application of pretilachlor @ 0.75 Kg ha-1fb Bispyribac sodium @ 20 g a.i. ha-1 (W1) was found most effective in reducingtotal weed density.Higher yield and yield attributes were found under CPT which was significantly higher than the UPF and at par with FIRB. Amongweed management practices highest yield and yield attributes were obtained with pretilachlor @ 0.75 Kg ha-1fb Bispyribac sodium @ 20 g a.i. ha-1.Lowest yield and yield attributes were obtained in weedy check.
 Conclusion: Puddled transplantation in rice might be the best option to get higher yield and for weed control, application of Pretilachlor @ 0.75 Kg ha-1 PE fb Bispyribac sodium @ 20 g a.i. ha-1 POE at 20 DAT may be done to get higher yield.

The impact of aqueous and N-hexane extracts of three Fabaceae species on seed germination and seedling growth of some broadleaved weed species.

Weed infestation is a persistent problem for centuries and continues to be major yield reducing issue in modern agriculture. Chemical weed control through herbicides results in numerous ecological, environmental, and health-related issues. Moreover, numerous herbicides have evolved resistance against available herbicides. Plant extracts are regarded as an alternative to herbicides and a good weed management option. The use of plant extracts is environmentally safe and could solve the problem of herbicide resistance. Therefore, laboratory and wire house experiments were conducted to evaluate the phytotoxic potential of three Fabaceae species, i.e., Cassia occidentalis L. (Coffee senna), Sesbania sesban (L.) Merr. (Common sesban) and Melilotus alba Medik. (White sweetclover) against seed germination and seedling growth of some broadleaved weed species. Firstly, N-hexane and aqueous extracts of these species were assessed for their phytotoxic effect against lettuce (Lactuca sativa L.). The extracts found more potent were further tested against germination and seedling growth of four broadleaved weed species, i.e., Parthenium hysterophorus L. (Santa-Maria), Trianthema portulacastrum L. (Pigweed), Melilotus indica L (Indian sweetclover). and Rumex dentatus L. (Toothed dock) in Petri dish and pot experiments. Aqueous extracts of all species were more toxic than their N-hexane forms for seed germination and seedling growth of lettuce; therefore, aqueous extracts were assessed for their phytotoxic potential against four broadleaved weed species. Aqueous extracts of all species proved phytotoxic against T. portulacastrum, P. hysterophorus, M. indica and R. dentatus and retarder their germination by 57, 90, 100 and 58%, respectively. Nevertheless, foliar spray of C. occidentalis extract was the most effective against T. portulacastrum as it reduced its dry biomass by 72%, while M. alba was effective against P. hysterophorus, R. dentatus and M. indica and reduced their dry biomass by 55, 68 and 81%, respectively. It is concluded that aqueous extracts of M. alba, S. sesban and C. occidentalis could be used to retard seed germination of T. portulacastrum, P. hysterophorus, M. indica and R. dentatus. Similarly, aqueous extracts of C. occidentalis can be used to suppress dry biomass of T. portulacastrum, and those of M. alba against P. hysterophorus, R. dentatus. However, use of these extracts needs their thorough testing under field conditions.

Training Need Assessment of rice farmers regarding weeds and their management in Punjab, Pakistan

The training needs of rice growers in Punjab, Pakistan were assessed regarding the production technology used in growing rice. Total 332 rice growers were selected through random sampling technique from tehsil Nowshera Virkan, district Gujranwala and interviewed accordingly through a face-to-face interview technique. Data were analyzed using Statistical Package for Social Sciences (SPSS). Findings indicated that farmers had adequate awareness about the weeds and their management. The demonstration was the most effective technique as used by the extension field staff to create awareness among farmers about weeds management. Social media and electronic media use were appeared least effective. This indicates that farmers were more convenient with the traditional technique of creating awareness. Regarding training needs, Rice farmers had maximum training needs regarding chemical control and identification of rice weeds. Resourceful, cost-effective, and timely weed management options are pivotal to making rice crop profitable. Thus, Agriculture Department, Punjab should be aimed at empowering the rice farmers technically, to train them through both conventional approaches (i.e. demonstration plots) and technology-led approaches (i.e. Information Communication Technologies (ICTs), social media and electronic media).

Seedbank persistence and emergence pattern of Argemone mexicana, Rapistrum rugosum and Sonchus oleraceus in the eastern grain region of Australia

A thorough understanding of the emergence pattern and persistence of weed seeds is a prerequisite in framing appropriate weed management options for noxious weeds. In a study conducted at the University of Queensland, Australia, the emergence and seed persistence behavior of three major weeds Sonchus oleraceous, Rapistrum rugosum, and Argemone mexicana were explored with seeds collected from Gatton and St George, Queensland, Australia, with an average annual rainfall of 760 and 470 mm, respectively. Seed persistence was evaluated by placing seeds at the surface layer (0 cm) or buried at 2 and 10 cm depths enclosed in nylon mesh bags and examined their viability for 42 months. In another study, the emergence pattern of four populations, each from these two locations, was evaluated under a rainfed environment in trays. In the mesh-bag study, rapid depletion of seed viability of S. oleraceous from the surface layer (within 18 months) and lack of seed persistence beyond two years from 2 and 10 cm depths were observed. In trays, S. oleraceous germinated 3 months after seeding in response to summer rains and there was progressive germination throughout the winter season reaching cumulative germination ranging from 22 to 29% for all the populations. In the mesh-bag study, it took about 30 months for the viability of seeds of R. rugosum to deplete at the surface layer and a proportion of seeds (5 to 13%) remained viable at 2 and 10 cm depths even at 42 months. Although fresh seeds of R. rugosum exhibit dormancy imposed due to the hard seed coat, a proportion of seeds germinated during the summer months in response to summer rains. Rapid loss of seed viability was observed for A. mexicana from the surface layer; however, more than 30% of the seeds were persistent at 2 and 10 cm depths at 42 months. Notably, poor emergence was observed for A. mexicana in trays and that was mostly confined to the winter season.

Economical Efficacy of Weed Management Options in Groundnut + Pigeonpea Relay Intercropping System

Aims: To evaluate the effect of different weed management options on the economics in groundnut + pigeonpea relay intercropping on medium black clayey soils of Junagadh .
 Study Design: Field experiment was conducted at Junagadh during kharif 2019-20 and 2020-21 in Randomized Block Design with three replications to evaluate the effect of different weed management options on the economics in groundnut + pigeonpea relay intercropping on medium black clayey soils. The treatments comprised of: pendimethalin 0.9 kg ha-1 as PE fb interculturing and hand weeding at 45 DAS, pendimethalin 0.45 kg ha-1 + oxyfluorfen 0.09 kg ha-1 as PE fb interculturing and hand weeding at 45 DAS), interculturing and hand weeding at 15 DAS fb sodium acifluorfen 16.5% + clodinafop propargyl 8% (ready mix) 1 kg ha-1 at 45 DAS as POE, interculturing and hand weeding at 15 DAS fb quizalofop p ethyl 40 g ha-1 at 45 DAS as POE, interculturing and hand weeding at 15 DAS fb propaquizafop 70 g ha-1 at 45 DAS as POE, pendimethalin 0.9 kg ha-1 as PE fb sodium acifluorfen 16.5% + clodinafop propargyl 8% (ready mix) 1 kg ha-1 at 45 DAS as POE, pendimethalin 0.9 kg ha-1 as PE fb quizalofop p ethyl 40 g ha-1 at 45 DAS as POE, pendimethalin 0.9 kg ha-1 as PE fb propaquizafop 70 g ha-1 at 45 DAS as POE (T8), weed free, and unweeded control (T10).
 Place and duration of the study: Instructional Farm, Department of Agronomy, College of Agriculture, Junagadh Agricultural University, Junagadh during kharif seasons of 2019-20 and 2020-21.
 Methodology: on the basis of prevailing local charges. The gross realization in terms of rupees per hectare. A net return of each treatment was calculated by deducting the total cost of cultivation from the gross returns.
 Result: Significantly higher amount of gross returns were recorded with the weed free treatment (T9), which was closely followed by interculturing and hand weeding at 15 DAS fb sodium acifluorfen 16.5% + clodinafop propargyl 8% (ready mix) 1 kg ha-1 at 45 DAS as PoE (T3). Statistically higher net returns and higher net returns and B:C ratio were registered with interculture and hand weeding at 15 DAS fb sodium acifluorfen 16.5% + clodinafop propargyl 8% (ready mix) 1 kg ha-1 at 45 DAS as PoE (T3).

Weed prevalence and productivity of transplanted rice influences by varieties, weed management regimes and row spacing

ABSTRACT In input intensive agriculture, weeds are major biotic constraints which are likely to increase and become more complex. Overreliance on single weed management practice may further exaggerate weed severity and also invite adverse effect, therefore, urgent technological intervention adopted on eco-friendly integrated weed management to improve weed control and sustaining the productivity in transplanted rice. The aim of the study was to compare two popular rice varieties (‘Swarna’ and ‘Mahamaya’) with two row spacing (15 and 20 cm) along with three weed management regimes [weedy, bispyribac sodium 25 g ha-1 and two hand weeding at 20 and 40 days after transplanting (DAT)] on weed suppression and rice productivity. Our findings suggest that Swarna at 15 cm spacing along with two hand weeding enhance the weed suppression and provides higher rice productivity and can be adopted as integrated weed management options to minimize yield loss due to weeds competition in the region. In the study, more than two factors of weed management have been attempted which provide additional information to researcher, policy makers and rice growers to choose and disseminate real integration of weed management options.

Effect of Critical Period of Weed Competition and Its Management Option in Sweet Corn [Zea mays (L.) var. saccharata strut] Production: A Review

Sweet corn [Zea mays (L.) var. saccharata strut] is the most important variety of maize with high sugar content. It contains a glossy sweetish endosperm and primarily grown for human food. It requires moderately high temperature from 22oC up to 33oC, high light intensity and adequate and well distributed rainfall of not less than 200mm during growing season. It can be grown on the wide range of soils. However, it performs best on neutral, well drained, well aerated and moderately heavy, deep fertile soils. Sweet corn is not so much competing with weeds like other crops. Avoid the influence of weed competition on the growth and development of sweet corn produce maximum yield and the economic importance of sweet corn used for conception and health benefits. By so far it is good in health and as medicinal uses it should be managed without affecting by weeds. The weed management option properly controls by the method of mechanical, biological, chemical and integrated weed management. In general, it is significant that properly controlling critical period weed competition in sweet corn reducing the competition of light, water, nutrient and space and maximizing the yield of sweet corn.

Defining Integrated Weed Management: A Novel Conceptual Framework for Models

Weed population dynamics models are an important tool for predicting the outcome of alternative Integrated Weed Management (IWM) scenarios. The growing problem of herbicide resistance has increased the urgency for these tools in the design of sustainable IWM solutions. We developed a conceptual framework for defining IWM as a standardised input template to allow output from different models to be compared and to design IWM scenarios. The framework could also be used as a quantitative metric to determine whether more diverse systems are more sustainable and less vulnerable to herbicide resistance using empirical data. Using the logic of object-oriented programming, we defined four classes of weed management options based on the stage in the weed life cycle that they impact and processes that mediate their effects. Objects in the same class share a common set of properties that determine their behaviour in weed population dynamics models. Any weed control “event” in a system is associated with an object, meaning alternative management scenarios can be built by systematically adding events to a model either to compare existing systems or design novel approaches. Our framework is designed to be generic, allowing IWM systems from different cropping systems and countries to be compared.

Phytotoxic Substances Involved in Teak Allelopathy and Agroforestry

Teak (Tectona grandis L.f.) is one of the most valuable timber species, and is cultivated in agroforestry systems in many countries across the tropical and subtropical regions of the world. The species is also one of the most essential trees in home gardens in South Asia due to its wood quality and medicinal value in folk remedies. It is a deciduous tree species, and the amount of litter that falls from teak trees is huge. The decomposition rate of the litter is relatively fast in tropical humid conditions. The interactions between teak and weeds, or crops, under the teak trees have been evaluated in terms of allelopathy. Evidence of allelopathy is documented in the literature over the decades. The leachate and extracts of teak leaves suppress the germination and growth of several other plant species. Phytotoxic substances, such as phenolics, benzofurans, quinones, terpens, apocarotenoids and phenylpropanoids, in the teak leaves, were isolated and identified. Some phytotoxic substances may be released into the soil under teak trees from leaf leachate and the decomposition of the litters, which accumulate by annual leaf fall and can affect the germination and growth of undergrowth plant species as allelopathic substances. The allelopathy of teak is potentially useful for weed management options in agroforestry and other agriculture systems to reduce commercial herbicide dependency. It was also reported that agroforestry systems with teak enhance income through the production of crops and woods, and provide energy efficiency for crop cultivation.