Weed Science

A field experiment was conducted during Kharif seasons of 2014-15 and 2015-16 at Bidhan Chandra Krishi Viswavidyalaya (BCKV), West Bengal to evaluate the effect of pretilachlor 50% EC on growth of composite weed flora and productivity of winter (Kharif) rice (Oryza sativa L.). The experiment comprised of eight treatments following a randomized block design with three replications. Experimental findings revealed that hand weeding twice at 15 and 30 DAT effectively controlled the grasses, sedges and broad-leaved weeds, which recorded statistical parity with the application of pretilachlor 50% EC at 750 g/ha followed by its lower dose at 600 g/ha. Grain yield losses amounted to 31.4-50.1% due to uncontrolled weed growth as compared to different weed control treatments. Among the different herbicidal treatments, pretilachlor 50% EC at 750 and 600 g/ha recorded higher weed control efficiency, yield attributes and grain yield (4.25 and 4.20 t/ha, respectively) of rice, which did not affect the germination and seed yield of succeeding lentil crop during both the years. Besides, soil beneficial microflora was not negatively influenced in long run. Considering bio-efficacy, economics and microbial study, pretilachlor 50% EC at 600 g/ha could be a better alternative for weed management and may be recommended for obtaining a higher yield of transplanted winter rice in the Gangetic Inceptisol of West Bengal.

Direct-seeded rice (DSR) helps in saving water and is beneficial for soil physical health along with environmental benefits, but weeds poses a serious threat to efficient crop production. In the absence of ponded water, weeds emerge in several flushes making it difficult to manage them with a single pre- or post-emergence herbicide application.  Studies were carried out under the screen house conditions at CCS Haryana Agricultural University, Hisar, where the response of four dominant grass weeds of direct-seeded rice, viz. Echinochloa glabrescens, Leptochloa  chinensis, Eragrostis japonica and  Dactyloctenium  aegyptium was evaluated against pendimethalin and cyhalofop-butyl + penoxsulam mixture. The four grassy weed species were planted in pots replicated four time with 20 seed per plot. Pendimethalin was applied as pre-emergence at 0.25, 0.5, 1.0 and 2.0 kg/ha and cyhalofop-butyl + penoxsulam mixture was sprayed as post-emergence (PoE) (at 25 days after sowing) at 32.5, 65, 135 and 270 g/ha with the help of knapsack sprayer and control pots were maintained for each species and herbicides. Periodical observations on visual mortality (0-100 scale, where 0 = no effect and 100=complete mortality) and dry weight per pot was observed at harvest. Application of pendimethalin at 1.0 kg/ha resulted in excellent control of L. chinensis and D. aegyptium, whereas at 2.0 kg/ha application rate killed all the weeds. Cyhalofop-butyl + penoxsulam applied at 270 g/ha showed 100% mortality of E. glabrescens and L. chinensis.  However, the highest rate (270 g/ha) of this mixture had no effect on E. japonica, and provided only 20% control of D. aegyptium. Results of this study suggest that pendimethalin can be used for managing E. glabrescens, L. chinensis, E. japonica and D. aegyptium. However, cyhalofop-butyl + penoxsulam can be used as PoE in fields dominated by E. glabrescens and L. chinensis.

An experiment was conducted during 3 consecutive rainy seasons of 2015 to 2017 at ICAR-Research Complex for Eastern Region, Patna to evaluate the mechanized weed management practices for enhancing the productivity in system of rice intensification (SRI) against farmers’ practice. The seven weed management treatments, viz. conoweeder thrice at 15, 25 and 35 DAT, conoweeder twice at 15 and 30 DAT, post-emergence (PoE) application of bispyribac-Na 25 g/ha (20 DAT) + conoweeder at 35 DAT, conoweeder 15 DAT + bispyribac-Na 25 g/ha (20 DAT), conoweeder on 15 DAT + bispyribac-Na 25 g/ha (20 DAT) + conoweeder 35 DAT, unweeded check and farmers’ practice were evaluated under randomized block design with three replications. Fimbristylis miliacea was the top ranking weed with the highest degree of weed infestation. Significantly the highest grain yield (5.97 t/ha) was obtained from 3 times conoweeder at 15, 25 and 35 DAT, which was at par with conoweeder twice on 15 and 30 DAT (5.40 t/ha). Integration of herbicide with mechanical weeder did not improve the weed control efficiency and grain yield over conoweeder twice on 15 and 30 DAT. The highest weed control efficiency of 93.3 and 91.7% at 60 DAT were obtained with application of conoweeder thrice at 15, 25 and 35 DAT and conoweeder twice at 15 and 30 DAT, respectively. The crop raised by SRI method produced significantly higher grain and straw yields than that of farmers’ practice except unweeded check under SRI, which was heavily infested with weeds (weed density 153.27/m2 and weed biomass 129.93 g/m2). However, in SRI, 2 times conoweeder at 15 and 30 DAT, was found to be effective and economical leading to cost saving for the farmers.

During 2014-17, an on-farm research trial was conducted at five farmer fields in Katni district of Madhya Pradesh to validate, refine and popularize the technology for managing Commelina benghalensis L. The study aimed to find out the efficacy of bispyribac-sodium 20 g/ha, pyrazosulfuron 20 g/ha and pendimethalin 1.5 kg/ha over farmers practice (hand weeding twice at 30 and 60 DAT) and unweeded control on the management of weeds and profitability of rice (Oryza sativa) sown in transplanted condition. Bispyribac-sodium 20 g/ha at 20-21 DAT reduced the density of C. benghalensis upto 9.8 no./m2 and dry weight upto 6.9 g/m2 and also reduced the infestation of other weeds to a significant extent. Higher values of yield attributes such as number of panicles (229/m2), grain yield (3.46 t/ha) and net returns (` 31820/ha), as well as less values of nutrient uptake by weeds (5.8 kg N, 1.1 kg P and 6.9 kg K/ha) were recorded with this herbicide compared to farmers practice.

A long-term field experiment from 1999-2000 to 2015-16 at CCS Haryana Agricultural University, Regional Research Station, Karnal, Haryana, India was done to study the effect of green manuring and continuous or rotational use of herbicides on weeds and productivity of the rice-wheat cropping system. Based on data from 2008-09 onward, the density of grassy weeds in the weedy plots under green manuring (GM) (7-37 plants/m2) remained lower or equal to treatments without green manuring (WGM) (6-37 plants/m2) in rice with few exceptions. Similarly, broad-leaf weeds (BLW) and sedges under GM (0-83 plants/m2) remained lower or similar to WGM (0-106 plants/m2) across different years. In wheat, the density of Phalaris minor was higher or similar under GM (55-229 plants/m2) than WGM (45-177 plants/m2), while the converse was true for BLW (19-275 plants/m2 and 45-405 plants/m2, respectively). The most dominant weed Echinochloa crus-galli in rice and Phalaris minor in wheat did not develop any envisaged sign of herbicide resistance against continuous and rotational used herbicides in respective crops. Grain yields of rice under weed-free situations were better under GM (6.37-8.30 t/ha) than WGM (5.59-7.63 t/ha). Similarly, the grain yields of wheat were higher under GM (5.25-5.99 t/ha) than WGM (5.08-5.54 t/ha). Consequently, the overall system productivity was better under GM.

A field trial was conducted at Regional Research Station (coastal saline zone), BCKV, Akshaynagar, Kakdwip, South 24 Parganas (WB) during winter seasons of 2016-17 and 2017-18 to study the bio-efficacy of pinoxaden against the canary grass (Phalaris minor) and wild oat (Avena ludoviciana) in wheat and its effects on succeeding greengram crop. Application of pinoxaden at 352.9      g/ha recorded significantly greater reduction of targeted weed populations; however, it was statistically at par with its two lower doses of 156.86 and 176.47 g/ha. The higher dose of pinoxaden had greater weed control efficiency (WCE). Pinoxaden at 352.94 g/ha resulted in significantly higher grain yield compared to other treatments. Lower doses of pinoxaden at 156.9 and 176.5 g/ha were at par with hand weeding for grain yield. Therefore, the application of pinoxaden 352.94 g/ha at 30 days after sowing (DAS) can be a good option for canary grass and wild oat management in wheat - greengram sequence in coastal Bengal.

A field experiment was laid out in a randomized block design consisting of metsulfuron-methyl (a herbicide) treatments at 2, 4, 8 g/ha along with control during two consecutive years to study metsulfuron-methyl degradation in soil and terminal residues in wheat straw and grain. Soil samples were collected at 0 (4 hr), 1, 3, 7, 10, 15, 30, 45, 60, 75 and 90 days after herbicide application for degradation studies. Wheat straw and grain were collected at the time of harvest for terminal residues study. The herbicide residues were quantified using high performance liquid chromatography (HPLC) equipped with UV-Vis detector using C-18 column. The degradation data generated in the present investigation during both the years indicated that higher dose of metsulfuron methyl i.e. 8 g/ha persisted in soil upto 45 days after herbicide application. The degradation was rapid and more than 90% of applied metsulfuron-methyl in soil dissipated within 15 days of application. The logarithmic plots of herbicide concentration at different doses versus time fitted first order kinetics decay curves during both years. At the time of harvest, the metsulfuron-methyl residues were non-detectable level in wheat straw and grain. Thus, the use of metsulfuron-methyl in wheat could be considered safe.

A field experiment was conducted during Kharif season to study the efficacy of different pre- and post-emergence herbicides for weed management in greengram. Pre-emergence (PE) application of pendimethalin + imazethapyr at 0.75 kg/ha (pre-mix) effectively reduced both the density and dry matter of weeds whereas post-emergence (PoE) application of imazethapyr 10 SL at 55     g/ha significantly reduced Cyperus rotundus. All the PE and PoE herbicides significantly reduced the dry weight of weeds at 30 and 60 days after sowing (DAS) as compared to weedy check. The highest weed control efficiency was recorded in two hand weeding (90.2%), and was followed by pendimethalin + imazethapyr (pre-mix) 0.75 kg/ha applied as PE (86.8%). PoE herbicides (imazethapyr, imazamox+ imazethapyr and clodinafop-propargyl + aciflourfen-sodium) not only suppressed the crop growth, but also exhibited antagonistic effect on root nodulation. Significantly higher seed yields were recorded under two hand weeding and pendimethalin + imazethapyr at 0.75 kg/ha (PE). Two hand weeding also recorded the highest gross and net returns, and was followed by pendimethalin + imazethapyr (pre-mix) at 0.75 kg/ha (PE). Application of pendimethalin + imazethapyr at 0.75 kg/ha (PE) also gave the highest B:C ratio, and it was followed by two hand weeding. All the PoE herbicides fetched comparatively lower returns and B:C ratio.

The field experiments were conducted during Kharif 2016 and 2017 at Research Farm, College of Agriculture, RVSKVV, Gwalior (M.P.) to study the effective herbicide/combination of herbicides to control the problematic weeds in greengram (Vigna radiata). The experiments were laid out with ten treatments, viz. quizalofop-p-ethyl 50, 75 and 100 g/ha PoE, fenoxaprop-p-ethyl 100 g/ha PoE, pendimethalin 1000 g/ha pre-emergence (PE), pendimethalin + imazethapyr (RM) 750 and 1000 g/ha PE, imazethapyr + imazamox (RM) 80 g/ha PoE, two hand weeding at 20 and 40 DAS and weedy check in a randomized block design. The combination of imazethapyr + imazamox (RM) 80 g/ha applied as post-emergence was found to be very efficient in controlling the dominant grassy as well as broad-leaved weeds and produced maximum seed yield (993 kg/ha), and was at par with two hand weedings at 20 and 40 DAS (983 kg/ha) and combination of pendimethalin + imazethapyr 750 g/ha and 1000 g/ha PE (844 and 758 kg/ha, respectively). Application of imazethapyr + imazamox (RM) 80     g/ha PoE resulted in the highest B:C ratio (3.03), and net returns, fb pendimethalin + imazethapyr 750 g/ha PE and two hand weeding at 20 and 40 DAS.

Field experiments 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 ammonium sulphate and 125% of recommended fertility, were conducted  at village Ganghala (Bhiwani) during Rabi seasons of 2014-15 and  village Bidhwan (Bhiwani) during 2015-16. 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 fb pendimethalin (PPI) at 0.75 kg/ha fb HW at 60 DAS did not prove effective in minimizing density of Orobanche. Post-emergence application of glyphosate at 25 and 50 g/ha at 25 and 55 DAS, respectively showed promising results with 75- 95% control of this weed in experimental field and 76.5% on large scale demonstrations at farmers’ fields. Biotype from Ganghala (Bhiwani) was found to be most robust biotype with 5840 seeds per capsule.

A field experiment was conducted at AICRP on Weed Management Farm, BACA, AAU, Anand Gujarat during two consecutive Rabi season of 2016-17 and 2017-18 on loamy sand soil to study the effect of integrated weed management in garlic with and without rice straw mulch. The experiment was laid out in Split Plot design (SPT) with three replications. Rice straw mulch 5.0     t/ha applied after planting in conjunction with either application of oxyfluorfen 240 g/ha PE fb HW at 60 DAP or tank mix application of pendimethalin 500 g/ha + oxyfluorfen 120 g/ha EPoE recorded significantly lower density and dry weight of weeds at harvest with higher weed control efficiency (91.9 and 85.9%, respectively), bulb weight (17.3 and 14.0 g/bulb, respectively), bulb yield of garlic (8.83 and 7.91 t/ha, respectively) along with the highest net return and B:C ratio.

In present study, biomass production and nutrient status (NPK) of weeds in three land use systems (canal bunds, fallow land and in cultivated land) at two locations (Ludhiana and Sangrur) of Punjab was analyzed throughout year (Jan-Dec 2017) at monthly interval. In case of land use systems fallow land (Sangrur) was recorded to have maximum total biomass (5.73 t/ha), nitrogen (96.9 kg/ha), phosphorus (21.5 kg/ha) and potassium (85.9 kg/ha). With respect to months, total maximum weed biomass production (7.40 t/ha), nitrogen (147.8 kg/ha), phosphorus (27.8 kg/ha) and potassium (125.8 kg/ha) was recorded in July. Thus from present data it is revealed that weeds which grow lavishly in fallow lands of Punjab possess high nutrient value and dry matter production of weeds in this land use system increased with heavy rainfall.

Removal of heavy metals by the invasive alien weed greater club rush (Scirpus grossus L. f) in a wetland ecosystem was estimated and compared with water hyacinth (Eichhornia crassipes) to assess its efficiency as a phytoremediator. The study was conducted during October-December 2016 by collecting soil and plant samples from an industrially polluted locality in Thiruvananthapuram district, Kerala. Results showed that in both the species, the metal concentration was more in the root system than in the shoot portion. Total metal uptake pattern in greater club rush was Cu>Cr>Zn>Ni>Pb>Co>Cd>As, while in water hyacinth it was Cu>Zn>Ni>Cr>Pb>Co>As>Cd.  It was concluded that greater club rush with its huge biomass production (>30 t/ha), could remove many of the heavy metals from contaminated soils more efficiently than water hyacinth. Biological concentration factor (BCF), translocation factor (TF) and biological accumulation coefficient (BAC) calculated for assessment of heavy metal mobility also suggested that greater club rush has the potential to be utilised for phytoremediation of contaminated soils.

Maize is the third most important cereal crop in India and is most susceptible to weed management practices. Weeding is one of the costliest and laborious operations in crop cultivation. Most of the existing weeders are of horizontal type and very less work done on vertical axis rotary weeders and energy aspects of the weeding units. A study was under taken to develop non-powered self-propelling vertical axis rotary weeder to eliminate the external powering unit, which provides the energy to cut the weeds and soil. The developed weeder was tested in maize crop at 2 and 4 cm of operational depth and 15 and 30 DAS of crop growth stages. The developed weeder performed very well at all the crop growth stages and obtained a weeding efficiency of 65 to 70% with 1.98 to 5.88% of plant damage. The highest cob yield of 12.9 t/ha was recorded weeding at 15 DAS followed by 30 DAS. However a care must be taken and a safety zone i.e. a gap of 7-10 cm between machine edges to the tip of plant leaves should be maintained to avoid the plant damage. At operational depth of 2 cm the draft force required to pull the weeding unit was 6.3 kgf and obtained field capacity was 0.08 ha/h, which was higher when weeder was operated at 4 cm of operational depth. 

The performance of different herbicides for the weed control of dry direct-seeded rice (DDSR) under zero tillage was evaluated by field experiment during rainy season of 2017 at NARC, Lalitpur, Nepal. The treatments consisted of 8 different herbicidal treatments (pendimethalin 1.0 kg/ha, pendimethalin 1 kg/ha followed by bispyribac-Na 35 g/ha, pendimethalin 1.0 kg/ha followed by (fb) tank mix of pyrazosulfuron 20 g/ha + bispyribac-Na 25 g/ha, pendimethalin 1.0 kg/ha fb 2,4-D 1.0 kg/ha, pendimethalin 1.0 kg/ha fb pyrazosulfuron 20 g/ha, pendimethalin 1.0 kg/ha fb penoxsulam 14 g/ha, pendimethalin 1.0 kg/ha fb sulfosulfuron 30 g/ha, pendimethalin 1.0 kg/ha fb 2,4-D 1.0 kg/ha under co-culture with Sesbania) and a weedy check treatment with 3 replications under randomized complete block design. Result of the experiment revealed significant reduction in the weed density and increase in rice yield due to application of herbicides. Sequential application of pendimethalin (pre) fb tank mixture of pyrazosulfuron + bispyribac-Na (post) possess higher weed control efficiency and yielded the highest rice grain yield (3.78 t/ha), which was statistically at par with pendimethalin fb 2,4-D under Sesbania co-culture (3.44 t/ha) and pendimethalin 1.0 kg/ha fb penoxsulam 14 g/ha (3.09 t/ha). Similarly, application of pendimethalin 1.0 kg/ha (pre) fb tank mixture of pyrazosulfuron 20 g/ha + bispyribac-Na 25 g/ha recorded the highest net returns of NRs. 31,760/ha and B: C ratio of 1.42 resulting to be the most economical and efficient herbicidal treatment option in DDSR under zero tillage.

Three herbicidal mixtures, viz. triafamone 20% + ethoxysulfuron 10% (pre-mix) 67.5 g/ha, 12 days after sowing (DAS), cyhalofop-butyl+ penoxsulam 6% OD (pre-mix) 150 g/ha, 20 DAS, and fenoxaprop-p-ethyl 6.9 EC 60 g/ha+ ethoxysulfuron 15 WDG (tank mix) 15 g/ha, 20 DAS were evaluated for their efficacy against weeds in wet-seeded rice. These treatments were compared with bispyribac-sodium, hand weeding twice and unweeded control. Application of triafamone + ethoxysulfuron, and cyhalofop-butyl + penoxsulam, significantly reduced the weed biomass followed by the treatments bispyribac-sodium, and hand weeding at 60 DAS. Fenoxaprop-p-ethyl + ethoxysulfuron had significantly lower weed control efficiency, probably due to its inability to control Echinochloa crus-galli effectively. Considering rice grain and straw yields, all herbicide treatments were at par except for fenoxaprop-p-ethyl + ethoxysulfuron, which recorded significantly lower values. Among yield attributes, significantly higher number of panicles/m2 was recorded in the treatments triafamone + ethoxysulfuron, and hand weeding, followed by cyhalofop-butyl+ penoxsulam. Grain and straw yields were lowest in unweeded control

A field study was conducted at ICAR-Research Complex for NEH Region, Basar during 2012-13 to study the effect of planting methods, row arrangement and mulching on toria (Brassica campestris L.) and associated weeds. Results revealed that at 30 and 60 days after sowing (DAS), the weed density and weed dry biomass were lesser in ridge and furrow; among row arrangement lower weeds at 6 rows followed by 3 rows over normal row planting. However, between the mulch, at 30 DAS the lower density and dry biomass were recorded with groundnut haulm mulching at 4 t/ha over no mulch, whereas at 60 DAS, dramatically no mulch plots had lesser weeds as compared to mulched plots. The number of branches/plant, siliqua/plant, seeds/siliqua, seed and stover yields were higher in ridge and furrow at 6 rows arrangement with groundnut haulm mulch at 4 t/ha.

A field experiment was conducted during the summer seasons of 2016 and 2017 at Banka, (Bihar) to evaluate the effect of sowing dates and weed management on weeds and productivity of summer greengram (Vigna radiata L.). The experiment was laid out in a split plot design replicated thrice. Eleven weed species, viz. Cynodon dactylon, Dactyloctenium aegyptium, Digitaria sanguinalis, Panicum repens, Cyperus rotundus, Amaranthus viridis, Celosia argentea, Commelina benghalensis, Digera arvensis, Euphorbia hirta and Trichodesma indicum infested the greengram.Two hands weedings 20 and 40 days after sowing (DAS) recorded the lowest weed density and biomass which was significantly superior over rest of the weed management treatment. Pendimethalin (1000 g/ha) 2 DAS fb one hand weeding at 20 DAS gave significantly higher plant height, pods/plant, seeds/pod and seed index, higher seed yield, maximum net returns and B:C ratio and was found at par with two hands weeding at 20 and 40 DAS. Pendimethalin (1000 g/ha) 2 DAS fb 1 hand weeding at 20 DAS recorded the highest nutrient uptake N, P and K and was at par with of pendimethalin (1000 g/ha) 2 DAS during both years of experimentation.

A field experiment was conducted to study the effect of different high efficiency herbicides as pre- and post-emergence application on weed growth, yield and economics of groundnut at Tirupati campus of Acharya N.G. Ranga Agricultural University during Rabi, 2018. Among all the weed management practices, the broad-spectrum weed control with higher pod yield and benefit-cost ratio were obtained with pre-emergence application of diclosulam 20 g/ha followed by hand weeding at 40 DAS and next best option could be the pre-emergence application of diclosulam 20 g/ha followed by cycloxydim 100 g/ha at 20 DAS in sandy loam soils.

An experiment was conducted under All India Network Research Project on Onion and Garlic, operating at the College of Horticulture, Orissa University of Agriculture and Technology, Sambalpur, Odisha during Rabi, 2010-11 to compare the efficacy of different weed control methods in onion. The experiment was laid out in a randomized block design with eight combinations of weed management practices and replicated thrice. Results revealed that significantly highest marketable bulb yield (19.19 t/ha) and total bulb yield (22.80 t/ha) was obtained with a higher percentage ‘A’ grade bulb (34.04 %) and an average bulb weight (69.83 g) by the application of oxyfluorfen before planting + one hand weeding at 45 days after transplanting. The identical weed management practice recorded highest 66.09% of weed control efficiency along with the lowest number of monocot weeds (26.33/ m2), minimum fresh weight of weeds (40.08 g/m2) and minimum dry weight of weeds (14 g/m2). Imposition of manual hand weeding at 45 DAT facilitates a weed-free situation to the crop. Hence, it was concluded that maximum bulb yield can be obtained with the application of oxyfluorfen before planting + one hand weeding at 45 DAT due to the influence of oxyfluorfen and one manual hand weeding on monocot weeds during the crop growth period.

A field investigation was conducted during October, 2018 - March, 2019 at Port Blair, to assess the impact of seven mulching practices [areca nut leaves (chopped and unchopped), husk, silver oak leaves, and black polythene] on areca nut along with weed free and weedy check treatments in randomised complete block design (RCBD) with five replications. Tree is taken as a replication. Results revealed that weed free treatment biomass (259.1 g/m2) removed 82 kg (33.7 - 5.18 - 38.9 kg/ha of N-P-K) nutrients/ha. Black polythene mulching excluded the light supplies to weeds within 6 weeks time brought 100% weed control efficiency (WCE) and arrested the evapo-transpiration (ET) losses of weeds resulting in higher soil moisture content (SMC, %) in surface layer (0-10 cm). Organic mulches with lower WCE {77.63 (silver oak leaf mulch) - 92.93% (areca nut chopped leaf mulch)} than polythene mulching also contributed to higher SMC (0-10 cm). Mulching did not affect the SMC in deeper layer (10-30 cm). Weed free plots resulted in evaporation losses of moisture as that of ET losses of weedy check as evident form SMC. High cost of polythene mulches (` 41095/ha) when spread over its 5 year life span becomes cheaper than manual weeding (with recurring cost every year). However, due to every year organic mulching with farm generated residues soil organic matter may build up and thus enhances the water retention capacities and their ecological safety merits adoption. Soil (nutrient) and water conservation services of mulching in areca nut established in the study calls for its exploitation for weed management in islands.