Weed Science

Direct-seeded rice (DSR) is significant in modern day agriculture because it requires less water input (20%) and labour (65-80 person-days/ha). Moreover, it enables farmers to establish rice early, which allows the crop stand more power to resist flush flood happening more frequently in the beginning of the monsoon. Direct-seeded rice produces at par or higher yield compared to manual transplanted rice but significantly higher yield (1.07 t/ha) compared to traditional manual broadcasted rice followed by beushening practice. It helps to increase system productivity by 0.25 t/ha, increase income by US$ 150/ha, reduce greenhouse gas emission (20% GWP) besides instrumental in reducing straw burning and environmental footprints. Despite all these advantages, the DSR has not been adopted at large scale at farmers’ field in eastern India particularly in Bihar, Odisha and Uttar Pradesh. One of the most important reasons for this is heavy and diversified weed infestation in DSR which consequently reduces rice yields significantly. In the present review article, the authors have tried to compile relevant information on the weed management approaches in DSR with special reference to eastern Indian states. Detailed discussions on weed species based on their occurrence and infestation, critical period of weed competition and different methods of weed management in DSR in eastern Indian ecologies have been enlightened in this paper. It also includes that weed management options in DSR depend on many factors like land situation, soil condition, water status, planting geometry and resources availability; and therefore, one single method of weed management practices may not be sufficient to control all the flushes of diversified weeds. Integrated approach combining cultural, physical and chemical methods can provide a more robust control of weeds in DSR. Relevant data generated in Odisha representing eastern Indian ecologies have also been included herein to further enrich knowledge and skills regarding DSR productivity, in general and possible weed management options, in particular.

Greengram [Vigna radiata (L.) Wilczek], also known as mungbean, is extensively cultivated in India and other Asian countries. Being rich in protein, its grains are an important daily dietary component. Weeds are a major limiting factor in production of greengram that lead to a drastic reduction in yield. The presence of hardy weeds and slow initial crop growth compound this problem. Different strategies incorporating non-chemical and chemical methods have been practiced for efficient weed control in greengram. Non-chemical control methods include straw mulch (12-63% reduction in weed biomass), narrow row spacing (60-92% reduction in weed biomass), method of sowing (1-20% reduction in weed biomass), tillage practices (58% reduction in weed biomass), the frequency and rate of irrigation and fertilizer application (13-23% reduction in weed biomass), timing of hand weeding and selection of cropping system. Chemical control methods include the many herbicides with different selectivity and efficiency available for use in greengram. For efficient weed control, herbicides should be applied at the recommended rate and time in order to avoid inhibiting growth, symbiotic properties (number of nodules, dry weight of nodules, leghaemoglobin content in nodules) and grain yield in greengram crop. In this review, different weed management strategies including non-chemical and chemical weed control methods have been reviewed for their ability to control weeds in greengram. Furthermore, their influence on growth, symbiosis, yield and nutrient uptake of greengram, soil microflora and residual effect on succeeding crops have also been reviewed.

Environmental factors have significant implications on the biology of weeds, hence the study of biology of major weeds in a crop, could prove an ecological and economical viable tool for their management. Echinochloa glabrescens, Leptochloa chinensis, Eragrostis japonica and Dactyloctenium aegyptium are the major weeds of direct-seeded rice (DSR) and many other Kharif crops. The effect of temperature, pH and light was studied on the biology of these four weed species under laboratory conditions during the Kharif seasons of 2012 and 2013. Temperature regimes of 15, 20, 25, 30, 35, 40 and 45°C; pH 5.0, 7.0, 9.0 and 11.0 and light period of 0, 3, 6, 12, 24 and 48 hours were evaluated for their effects on germination, shoot and root growth. Conducive temperature for germination of all four-weed species was 35°C except Dactyloctenium aegyptium, which has maximum germination at 30°C. Similar to germination, maximum shoot and root length was recorded at 35°C in all the weed species except E. japonica, for which 30°C was the optimum. Seed germination was observed over a broad range of pH of all weed species; however, it was highest at pH 7.0. Echinochloa glabrescens was most sensitive to a given pH range among all the weed species. Light periods didn’t alter the process of germination, shoot and root growth. Manipulation of these factors at field level could be helpful in reducing the weed pressure in DSR by preventing their germination.

The research programme undertaken at Rice Research Station, Moncompu, Kerala Agricultural University, for the post-emergence management of weedy rice by direct contact application (DCA) of broad-spectrum non-selective herbicides using specially designed novel hand held weed wiper device could selectively dry the panicles of weedy rice at 60-65 DAS, taking advantage of the height difference of 15-20 cm between weedy rice and cultivated rice. The study revealed that DCA can be effectively done in weedy rice infested cropped field using non-selective herbicides, viz. glufosinate ammonium, paraquat dichloride or glyphosate at 10-15% concentration. Weed control efficiency by this method in terms of drying of the weedy rice panicles was as high as 83 to 88%. The device has been filed for Indian Patent at Patent Office, Chennai (Application No. 1763/CHE/2014 dated 01.04.2014). The technology can reduce the seed rain and buildup of soil seed bank of weedy rice. It is highly energy efficient, less labour intensive, and eco-friendly compared to hand weeding, cutting of weedy rice ear heads or application of large quantity of herbicides using sprayers. The device has become popular among the farming community of Kerala and transfer of technology of the device was done during 2015. The product is now marketed as ‘KAU Weed Wiper’ by M/s Raidco Ltd, for large scale manufacturing and sale to farmers

Field and farmer participatory trials were conducted from 2006-07 to 2012-13 to evaluate the efficacy of herbicides alone and in combination on complex weed flora in sugarcane + wheat intercropping system. Sulfosulfuron 25 g/ha, sulfosulfuron + metsulfuron (ready-mix) 32 g/ha, mesosulfuron + iodosulfuron (ready-mix) 14.4 g/ha, pinoxaden 50 g/ha, pinoxaden + metsulfuron 50 + 4 g/ha, pinoxaden + 2,4-D 50 + 500 g/ha, pinoxaden fb carfentrazone 50 fb 20 g/ha gave satisfactory control of Phalaris minor. However, pinoxaden treatments were superior to other herbicides in respect of grassy weed management. For control of broad-leaf weeds, tank-mix of metsulfuron or 2,4-D with pinoxaden were found effective. Ready-mix herbicides sulfosulfuron+ metsulfuron and mesosulfuron+ iodosulfuron were also found promising against complex weed flora in sugarcane + wheat intercropping system. Clodinafop 60 g/ha, fenoxaprop 100  g/ha and carfentrazone 20 g/ha were phyto-toxic to the sugarcane. Grain yields of wheat under sulfosulfuron, sulfosulfuron + metsulfuron (ready-mix), mesosulfuron + iodosulfuron (ready-mix), pinoxaden alone and in combination with metsulfuron, 2,4-D or carfentrazone were as good as weed free check. Similarly the cane yields under these treatments except pinoxaden fb carfentrazone and sulfosulfuron + metsulfuron (ready-mix) were at par with each other and also with weed free check. Sulfosulfuron 25 g/ha, sulfosulfuron+ metsulfuron (ready-mix) 32 g/ha, mesosulfuron+ iodosulfuron (ready-mix) 14.4 g/ha or pinoxaden 50 g/ha provided effective control (83-97%) of weeds including Phalaris minor over the years. These treatments provided higher grain yield of wheat (4.65-4.93 t/ha) and cane yield (85.5-91.1 t/ha) of sugarcane.

A field experiment was conducted during Kharif-Summer season of 2016-17 at research farm of AICRP-Weed Management, Anand Agricultural University, Anand, Gujarat to study the effect of different tillage and weed management options on physico-chemical and biological properties of soil under cotton-green gram cropping system. The tillage and weed management treatments did not show any significant effect on various physico-chemical properties of soil after harvest of cotton and greengram except on organic carbon content and available phosphorus. The tillage did not influence the microbial population in cotton but weed management options, IC + HW at 15, 30 and 45 DAS showed significant impact on total bacterial count and dehydrogenase activity in soil. The tillage had significant effect on actinobacteria count and dehydrogenase activity in greengram while weed management options exhibited significant effect on all the microbial observations except on total PSM count. It is inferred that combination of zero tillage + residue incorporation along with IC + HW at 15, 30 and 45 DAS in cotton and zero tillage + residue incorporation along with IC + HW at 20 and 40 DAS in green gram were most suitable option for cotton-greengram cropping system in Middle Gujarat condition.

A field experiment was conducted during Kharif-Summer season of 2016-17 at research farm of AICRP-Weed Management, Anand Agricultural University, Anand, Gujarat to study the effect of different tillage and weed management options on physico-chemical and biological properties of soil under cotton-green gram cropping system. The tillage and weed management treatments did not show any significant effect on various physico-chemical properties of soil after harvest of cotton and greengram except on organic carbon content and available phosphorus. The tillage did not influence the microbial population in cotton but weed management options, IC + HW at 15, 30 and 45 DAS showed significant impact on total bacterial count and dehydrogenase activity in soil. The tillage had significant effect on actinobacteria count and dehydrogenase activity in greengram while weed management options exhibited significant effect on all the microbial observations except on total PSM count. It is inferred that combination of zero tillage + residue incorporation along with IC + HW at 15, 30 and 45 DAS in cotton and zero tillage + residue incorporation along with IC + HW at 20 and 40 DAS in green gram were most suitable option for cotton-greengram cropping system in Middle Gujarat condition.

To study the efficacy of neem cake, soil drenching of metalaxyl, post-emergence application of glyphosate at very low concentrations alone and in combination with 1% solution of (NH4)2SO4 and 125% of recommended fertility, field experiments were conducted at the villages Ganghala and Bidhwan in Bhiwani district of Haryana during Rabi seasons of 2014-15 and 2015-16, respectively. Feasibility of adoption of results of studies conducted earlier on use of glyphosate 25 g/ha at 30 DAS and 50 g/ha at 55 DAS is being demonstrated by multi location field trials through farmers participatory approach in different parts of state during 2010-2016. Neem cake 400 kg/ha at sowing fb soil drenching of metalaxyl MZ 0.2% at 25 DAS fb glyphosate at 40 g/ha at 45 DAS or neem cake 400 kg/ha fb pendimethalin (PPI) at 0.75 kg/ha fb metalaxyl 0.2% at 25 DAS did not prove effective in minimizing density of Orobanche.

Post-emergence application of glyphosate at 25 and 50 g/ha with 1% solution of (NH4)2SO4 at 30 and 55 DAS showed promise with 85- 91% control of this weed not only in experimental fields but in large scale demonstrations on farmers’ fields.

To study the efficacy of neem cake, soil drenching of metalaxyl, post-emergence application of glyphosate at very low concentrations alone and in combination with 1% solution of (NH4)2SO4 and 125% of recommended fertility, field experiments were conducted at the villages Ganghala and Bidhwan in Bhiwani district of Haryana during Rabi seasons of 2014-15 and 2015-16, respectively. Feasibility of adoption of results of studies conducted earlier on use of glyphosate 25 g/ha at 30 DAS and 50 g/ha at 55 DAS is being demonstrated by multi location field trials through farmers participatory approach in different parts of state during 2010-2016. Neem cake 400 kg/ha at sowing fb soil drenching of metalaxyl MZ 0.2% at 25 DAS fb glyphosate at 40 g/ha at 45 DAS or neem cake 400 kg/ha fb pendimethalin (PPI) at 0.75 kg/ha fb metalaxyl 0.2% at 25 DAS did not prove effective in minimizing density of Orobanche. Post-emergence application of glyphosate at 25 and 50 g/ha with 1% solution of (NH4)2SO4 at 30 and 55 DAS showed promise with 85- 91% control of this weed not only in experimental fields but in large scale demonstrations on farmers’ fields.  

Ginger is known to be sensitive to weed infestation, which severely influences crop productivity and ultimately to the economic returns. Therefore, in-situ resource conservation like land configurations namely broad bed and furrow (BBF), ridge and furrow (R&F) and flatbed (FB) and mulches with Imperata cylendrica (IC), pine needle (PN), double mulching of paddy straw followed by weed biomass (PS) and no mulch (NM) were assessed in ginger. Results revealed that weed density and weed dry biomass at 60 and 120 days after planting (DAP) were considerably lower with BBF followed by R&F than NM. Among mulches, the application of PN recorded lower weed density and dry biomass at 60 and 120 DAP, whereas, at second sampling, there was dramatically reduction of weed dry biomass in PS than IC. The rhizome productivity was improved with BBF (39.3-47.3%) and PS (35.8-42.2%) than FB and NM, respectively. BBF configured plots obtained 46.7-55.3% higher net returns and per day returns with 27.4-34.7% improvement in benefit to cost ratio followed by R&F than FB. Similarly, PS recorded 43.1 to 46.7% higher net returns and per day returns with 34.3 to 40.7% higher benefit to cost ratio over NM. Therefore, suitable land configurations and the use of available crop residues and tree leaf litter as mulch are promising resource conserving sustainable production technologies for ginger cultivation.

Effective and efficient weed management strategies are essential to raise a successful onion crop. Therefore, to find out the economically feasible weed management practice, a field experiment was conducted at Sher-e-Kashmir University of Agricultural Sciences and Technology, Jammu, during 2015-16 and 2016-17. Five herbicides namely pendimethalin1.0 kg/ha, oxyfluorfen 0.15 kg/ha, alachlor 1.0 kg/ha, butachlor 1.0 kg/ha and quizalofop-ethyl 0.05 kg/ha were applied alone or in different combinations replicated thrice in randomized block design. Data was recorded on weed density, dry matter accumulation of weeds, weed control efficiency, weed index, herbicide efficiency index and yield parameters. Pre-emergence application of oxyfluorfen 0.15 kg/ha fb one hand weeding at 40-60 days after transplanting recorded the highest weed control efficiency and the lowest values of weed density, dry matter accumulation of weeds and weed index. The pre-emergence application of oxyfluorfen 0.15 kg/ha fb post-emergence application of quizalofop-ethyl 0.05 kg/ha at 40 DAT was also found to be equally effective in controlling the weeds in onion. The yield attributing traits such as average bulb weight and total bulb yield also exhibited the same pattern. However, the highest B: C ratio was recorded with pre-emergence application of oxyfluorfen 0.15 kg/ha fb post-emergence application of quizalofop-ethyl 0.05 kg/ha applied 40 DAT. Hence, this treatment can be used for controlling the prevalent weed flora in onion crop under Jammu condition.

Glyphosate was the commonly used herbicide in ber orchards in Punjab, India. This herbicide has been banned by State Government recently in the state. Therefore, there is a dire need to develop non- chemical approaches to check weeds in ber (Zizyphus mauritiana Lamk.) orchard. An experiment was conducted to study the influence of different orchard floor management practices on weed biomass, fruit yield and quality of ber at Punjab Agricultural University, Ludhiana (India). Different floor management practices, viz. mulching (rice straw, white polythene, black polythene), mechanical, glyphosate and weedy check were evaluated. Weed biomass recorded at monthly intervals from November to March under all floor management practices exhibited a significant reduction in weed growth as compared to the weedy check. White polythene mulch recorded higher weed growth with reduced weed biomass as compared to black polythene mulch due to the penetration of solar radiation leading to weed emergence and disintegration of white polythene sheet. The weed biomass in inter-cultivation and herbicide treatments was increased up to January, however, with second cultivation and herbicide spray, the growth of weeds under these treatments was checked up to February and again showed an increasing trend. Although, glyphosate suppressed the weeds and mechanical weeding reduced the weed density but the resurgence of weeds resulted in comparatively higher weed biomass, while, rice straw mulch exhibited promising results, with 87.1 and 91.2% reduction in total weed biomass during 1st and 2nd year, respectively. Application of rice straw mulch at 12.5 t/ha may help in weed management in ber orchards.

Weed invasions change the natural diversity and balance of ecological communities which threaten the survival of many plants and animals. Therefore, weed management is important as far as crop production is concerned. Further, impact assessment has been proven as a means of measuring the effectiveness of any agricultural technology in improving productivity, reducing the poverty and increasing the livelihood security of the farmers. Present study focuses on highlighting socio-economic status of the farmers and agencies which play significant role in dissemination of weed related information as well as effect of weed management technologies on weed intensity in rice and wheat crops. Results revealed that before adoption, some weeds like Cyperus difformis, Fimbristylis milliacea and Ludwigia parviflora were found in very high severity (>75%) level in rice, however, after adoption of improved weed management technologies they reached to low and moderate severity (<50%) in farmers’ fields. According to 4.3% of the farmers, Phalaris minor is still present in wheat with very high level of severity (>75%) in most of their fields. Analytic Hierarchy Process (AHP) revealed the major agencies which play important role in disseminating the weed management technologies to the farmers. Findings of  study stress on sensitizing different agencies and increasing their role in dissemination of weed management solutions to the farmers.

An experiment was conducted to find out the most effective method of weed management in elephant foot yam. The experiment was conducted under 10 different agro-climatic conditions of India including plains, hills and islands, etc. using RBD with 8 treatments and 3 replications, during 2017 and 2018. Cyperus rotundus, Cynodon dactylon and Commelina benghalensis were the predominant weeds at most of the locations. Among different treatments, hand weeding thrice at 30, 60, 90 days after planting (DAP) recorded taller plants (80.85 cm) with more pseudo stem girth, canopy spread (97.07 cm), leaf area (5435.37 cm2), corm yield (38.0 t/ha), and net returns ( 387253), which was at par with weed control ground cover mat mulching and application of glyphosate thrice at 30, 60 and 90 DAP. Lower weed density and biomass were recorded in treatment with weed control ground cover mat mulching, which was at par with glyphosate applied at 30, 60 and 90 DAP.

The experiment was conducted during Kharif season of 2017 at Research Farm of Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur, Madhya Pradesh. The soil of experimental site was sandy clay loam in texture, medium in organic carbon (0.62%), available nitrogen (285 kg/ha), available phosphorus (17.45 kg/ha) and potassium (260 kg/ha) with neutral pH (7.1). The dominant weeds associated with direct-seeded rice in the experimental field were mainly comprised of monocot (Echinochloa colona), sedge (Cyperus iria) and dicot weeds (Mollugo pentaphylla, Phylanthus niruri, Eclipta alba, Corchorus olitorius and Alternanthera philoxeroides).Experiment consisted of total ten treatments comprising of seven doses of bentazone 600, 800, 1000, 1200, 1600, 1800 and 2000 g/ha, 2,4-D 380 g/ha as post-emergence, hand weeding twice (20 and 40 DAS) including weedy check, were laid out in a randomized block design with 3 replications. The post-emergence application of bentazone at higher doses i.e. 1800 and 2000 g/ha was found effective in reducing the weed density of dicot weeds to a great extent.

A field survey was taken up in Coimbatore, Tamil Nadu state to know the dominant weed species competing in the lowland rice ecosystems to identify the major weeds and study the biology and phenology of the weed species.  Barnyard grass (Echinochloa crus-galli), blistering ammannia (Ammania bacciffera), false daisy (Eclipta alba) and Viper grass (Dinebra retroflexa) were found predominant in lowland and were selected for the study. The seeds of selected weeds were collected along with the inflorescence from the field pot culture and field studies. It was found that among the four lowland weeds, Echinochloa crus-galli and Eclipta alba germinated  6 days after sowing both in the pot as well as field study.  Ammania bacciffera was germinated earlier in pot culture (7 days) and  Dinebra retroflexa germinated earlier (7 days) in field condition. Weeds grown in field condition came to 50% flowering earlier than grown in pot culture. Total dry weight per plant at flowering was higher in Dinebra  retroflexa  both in field  and pot culture and at maturity, it was higher with Echinochloa crusgalli.  Total dry weight at maturity was 8-12 times more than at flowering for all the weeds. The numbers of seeds/plant was higher with Echinochloa crus-galli in both in pot culture and field study with 650 and 850 seeds/ plant respectively.

The field experiments were carried out at Ludhiana and Gurdaspur during Kharif 2017 to find out the influence of rice straw mulching and weed management treatments on weed density, weed dry matter and grain yield in maize. Use of rice straw mulch (PSM) at 9.00 and 6.25 t/ha recorded an average of 19.9 and 11.4% higher grain yield (5.91-6.21 and 5.46-5.81 t/ha), compared with no mulching (4.82-5.31 t/ha), respectively. The results showed that there was a reduction in average grain yield of 9.80 kg/ha with every increase in dry matter accumulation of weeds by 1.0 g/m2. Post-emergence application of tembotrione (0.088 and 0.110 kg/ha) proved to be more effective than the pre-emergence application of atrazine (0.8 and 1.0 kg/ha) for controlling different weed species in maize. Both the doses of tembotrione (0.088 and 0.110 kg/ha) in combination with rice straw mulch at 9.00 t/ha displayed significantly lower weed growth and higher grain yield of maize in comparison to other treatments. The results showed that tembotrione at 0.088 kg/ha (PoE) in combination with PSM at 9.00 t/ha can be applied in maize for getting higher productivity, as this combination helps to reduce 20% dose of herbicide.

A farmer’s participatory field experiment was conducted during two consecutive Rabi seasons of 2015-16 and 2016-17 at farmer’s fields in Badkisarari village of Gwalior district of Madhya Pradesh on clay loam soils to validate zero-till sowing of wheat crop in rice-wheat cropping system for realizing higher yield. Zero till sown wheat had significantly lesser weed dry biomass per unit area as compared to wheat sown in conventional and reduced tillage besides advancement of sowing by 20-25 days over conventional and reduced tillage sowing of wheat crop. The population of Phalaris minor, Avena ludoviciana, Avena fatua, Chenopodium album, Melilotus indica and Anagallis arvensis was reduced significantly under zero tillage as compared to conventional tillage. Excellent suppression in weed density and weed dry weight with higher levels of weed control efficiency and yield were obtained with zero till sown wheat. Zero tillage was also found better in terms of lesser cost of cultivation, higher net returns and B:C ratio.

A field experiment was carried out at Tamil Nadu Agricultural University, Coimbatore during Kharif and Rabi seasons of 2018-19 to study the effect of altered crop geometry without changing the total plant population with integrated weed management methods in irrigated maize (Zea mays L.) and their residual effects on succeeding Bengal gram (Cicer arietinum). Based on the results, it could be ascertained that planting pattern of 60 x 25 cm proved to be effective in reducing weed biomass and recorded significantly higher grain yield of about 6.48 t/ha which was at par with the spacing of 75 x 20 cm. Pre-emergence (PE) application of atrazine at 1.0 kg/ha + hand weeding or twin wheel hoe weeding at 35 DAS was at par with hand weeding twice at 20 and 35 DAS with respect to grain yield. Herbicidal methods of weed management like 2, 4-D and atrazine application did not exert any residual effect on the succeeding Bengal gram.

A field study was conducted for two years during Rabi season of 2012-13 and 2013-14 on the  fields of farmers’ of Jhunjhunu and Bikaner districts infested with broomrape (Orobanche) to test the efficiency of herbicides in mustard crop under AICRP on Weed Management at Agriculture Research Station, Swami Keshwanand Rajasthan Agricultural University, Bikaner. The experiment comprising ten weed control treatments consisting of neem cake (200 kg/ha) + pendimethalin 1.0 kg/ha, neem cake (200 kg/ha) + glyphosate 25 g/ha at 25 DAS, pendimethalin  0.75 kg/ha + glyphosate 35 g/ha + 55 g/ha at 25 and 55 DAS, pendimethalin 1.0 kg/ha, glyphosate 25 g/ha + 50 g/ha at 25 and 55 DAS, glyphosate 50 g/ha + 50 g/ha at 25 and 55 DAS, oxyfluorfen (200 g/ha), imazethapyr (20 g/ha), manual weeding and weedy check in a randomized block design with three replications. Among the different herbicides, application of glyphosate at 25 g/ha + 50 g/ha at 25 and 55 DAS  controlled broomrape effectively with nil phytotoxicity and produced significantly the highest seed yield in mustard during both the years over all the other herbicidal treatments.