Volume-54 | Issue-2(April-June)| Year 2022

High risk, Intermediate and low risk species, Plant invaders, Quarantine weeds, Weed risk assessment (WRA) 

Introduced plants may contribute to the economic losses to agriculture and exert a substantial financial burden on the resources available for the management of natural areas. Most of these taxa have the ability to become agricultural or environmental weeds, and therefore prior to permitting their entry, the risk/s needs to be evaluated. Weed risk assessments (WRA) are used to identify plant invaders before introduction. Thus, in order to recognize plant introductions that are likely to cause damage, we examined the weed risk assessment (WRA) of quarantine weeds (Gazette notification issued on 24th October, 2019), that are listed in Schedule VIII of Plant Quarantine Order, 2003 issued under the Destructive Insect & Pest Act (1914) of India. The weeds species selected for the present study are already included in the quarantine weeds list. However, the data on how much risk is posed by these weed species is not available in Indian context. Therefore, we have made an attempt to assess of risk posed by these weed species. The present study revealed that among the evaluated 54 species, 33, 16 and 4 species showed high risk, intermediate risk and low risk, respectively. The highest WRA score (35) was recorded for the species Senecio inaequidens DC. The WRA score 34 was recorded for 3 species namely Centaurea diffusa Lam., Senecio jacobaea L. and Solanum carolinense L.  Amongst these weeds the lowest WRA score (16) was observed in case of Cichorium spinosum L. 

Nanotechnology, Detoxification, Nanoencapsulation, Smart delivery, Weed management

Nanotechnology is rapidly becoming one of the most essential tool in modern agriculture and it has the potentiality to play major role in managing weeds too in agroecosystems as the emerging weed problems can not be solved by adoption of conventional methods alone. Nanoparticles can be synthesized in many ways using top-down approach or bottom-up approach. Among these, the green synthesis of nanoparticles using plant or microorganisms is the eco-friendly and safest method of nanoparticle synthesis. Nanoparticles have wide range of applications in managing weeds and overcoming perennial weed menace through exhausting weed seed bank, breaking weed seed dormancy by degrading germination inhibitors, inhibiting viable underground plant parts by exhausting food reserves, improving foliar absorption and translocation etc. They can also be used in smart delivery mechanism of herbicides for rainfed ecosystems and as slow-release nano formulations for season long weed control. Nano formulations currently used in weed management are nano-encapsulation, nano-carrier, nano emulsion, nano-adjuvants, nano-biosensors etc. Nanotechnology reduces the application rate of herbicides per hectare and minimise environmental pollution and CO2 emission. Nano formulations are effective against herbicide resistant weeds and enhances the rate of mitigation of herbicide residues in soils. The nanotechnology holds promise for attaining sustainable agriculture through their effective and judicious use in development and adoption of weed management technologies, particularly in under developed nations.

Direct-seeded rice, Dust mulching, Establishment method, Rice productivity, Weed management, Weed pressure

A field experiment was conducted during rainy seasons of 2018 and 2019 at the ICAR-Research Complex for Eastern Region Patna, Bihar to evaluate the effect of crop establishment methods and weed management treatments on weeds and productivity of direct-seeded rice (DSR). The treatments consisted of three upland DSR establishment methods, viz. zero-till direct-seeded rice:(ZT-DSR); conventional-till (CT)-dry DSR (CTDSR) and CTDSR-dust mulching, and three weed pressure maintenance treatments including: low weed pressure: maintained with pre-emergence (PE) application of pendimethalin (1.0 kg/ha) at 2 days after seeding (DAS) followed by (fb) post-emergence (PoE) application of bispyribac–Na (30 g/ha) PoE at 20 DAS fb hand weeding (HW) twice at 30 and 50 DAS; medium weed pressure: maintained with pendimethalin (1.0 kg/ha) PE at 2 DAS fb bispyribac–Na (30 g/ha) PoE at 20 DAS, and high weed pressure: maintained with pendimethalin (1.0 kg/ha) PE alone, in upland DSR under the middle Indo-Gangetic Plains (MIGPs). The major weeds recorded with upland DSR were Cyperus rotundus, Cynodon dactylon, Echinochloa colona, Brachiaria ramosa, Caesulia axillaris and Physalis minima. Significantly the lowest relative weed abundance, weed density and biomass were recorded in CT-DSR-dust mulching compared to ZT-DSR and CTDSR. Among the weed management treatment, maximum weed suppression was recorded in low weed pressure in comparison to medium and high-weed pressure management practices. Significantly higher grain yield (2.14 t/ha) and net returns ( 20869/ha) were obtained with CT-DSR-dust mulching. Hence, it may be concluded that for better rice productivity and weed management in upland DSR, CT-DSR-dust mulching with low weed pressure maintenance is the most potential and viable practices under the MIGPs.

Climate change, Crop-weed interaction, Rice, Elevated CO2, Elevated temperature, Weed competition

Rice (Oryza sativa L.) is one of the major staple food source for more than half of the global population. To attain the food needs of the world’s growing population, further increase in rice productivity is needed. To assess the sensitivity of agricultural output, a greater comprehension of the possible interactions amongst crops and weeds in the face of climate change, especially under elevated CO2 (EC) and elevated temperature (ET), is essential. This study was conducted to quantify the influence of elevated temperature, CO2, weed density and their interactions on crop-weed competition, rice yield parameters and grain yield. The experiment was conducted in four separate Open Top Chambers (OTCs), viz. with ambient CO2 (A), elevated CO2 [550±50 ppm] (EC), elevated temperature (ambient±2 °C) (ET) and combined effect of elevated CO2 and temperature (EC+ET) with and without weed competition. The EC alone enhanced the rice grain yield by 42.30% in weed-free conditions when compared to ambient CO2, however substantial change was not observed under ET. In the EC+ET condition, however, regardless of weeds presence or absence, crop output was reduced by 22.02 percent. Alternanthera paronychioides A. St.-Hil. competition caused rice yield reduction of 79.72, 83.04, 62.98 and 62.01% at A, EC, ET, EC+ET, respectively. The EC and ET interactions will certainly exert a profound influence on weed growth and competition against crops, which ultimately enhances crop yield losses in futuristic climate change scenario. 

Cultivated rice, Dormancy, Ecological variation, Germination, Morphotypes, Weed ecology, Weedy rice

Seed dormancy is an adoptive trait of weedy rice to persist in rice production system. Weedy races and wild relatives of rice exhibit variation in seed dormancy, which allows weedy rice to escape weed management practices, and increases the flowering synchronization pattern resulting in gene flow between weedy and cultivated rice. In this study, eighteen weedy rice morphotypes collected from different rice growing areas in India, along with two rice cultivars, were evaluated for their germination pattern across time. Weedy rice seed germination was recorded periodically at weekly intervals up to 35 weeks after sowing (WAS) under controlled conditions. Dormancy duration was computed and germination index was calculated at 27 WAS. Significant variability was observed in germination pattern among the weedy rice morphotypes studied. The weedy rice morphotypes collected from Uttar Pradesh (T68) attained 50% germination after a maximum duration of 13.5 WAS, while five morphotypes of weedy rice remained ungerminated at 3 WAS. Seven weedy rice morphotypes germinated at 3 WAS at which both the rice cultivars (BPT 5204 and Pusa 1101) have germinated (96.7 and 83.3%, respectively). Two weedy rice morphotypes had highest germination percentage (98.3%) at 35 WAS, while least (21%) was recorded with morphotype collected from Chhattisgarh (T41). This study indicated the existence of high degree of dormancy in weedy rice morphotypes. The findings of this study might be helpful for agronomists and farmers to develop and implement effective weedy rice management strategies at different rice production systems in India. 

Cyhalofop-butyl, Transplanted rice, XR-848 benzyl ester, Weed management, Weed control efficiency

A field experiment was conducted during rainy (Kharif) seasons of 2015 and 2016 at Agricultural Research Station, Dhadesugur, University of Agricultural Sciences, Raichur, Karnataka, India to evaluate the efficacy of XR-848 benzyl ester 20 g/l + cyhalofop-butyl 100 g/l EC (ready-mix) on weeds in transplanted rice. The dominant grassy weeds in the experimental field were: Echinochloa colona, Panicum repens, Cynodon dactylon, Brachiaria mutica, Digitaria sanguinalis and Leptochloa chinensis; broad-leaved weeds were: Eclipta alba and Ludwigia parviflora and the sedge was Cyperus rotundus. The post-emergence application (PoE) of XR-848 benzyl ester 20 g/l + cyhalofop butyl 100 g/l EC (ready-mix) 180 g/ha recorded significantly lower weeds biomass, higher weed control efficiency at 30, 45 and 60 days after transplanting (DAT) and higher rice grain yield during both the years and it was at par with XR-848 benzyl ester 20 g/l + cyhalofop butyl 100 g/l EC (ready-mix) 150 g/ha. The hand weeding twice at 20 and 40 DAT recorded significantly higher weed control efficiency and grain yield compared to other herbicide treatments.

Bispyribac-Na, Clodinafop + metsulfuron, Low-dose high-potency (LDHP), LDHP herbicide, Rice, Spraying technique, Weed control efficiency, Wheat

Efficient and effective methods of weed control are needed to ensure higher crop productivity and profitability. Herbicides use is becoming popular amongst farmers because of ease, efficiency and lesser cost involved. The efficacy of herbicide depends on the proper spraying technique. Recently, the new generation effective low-dose high-potency (LDHP) herbicide molecules are being introduced but their compatibility to the existing spraying techniques and practices is unknown. Hence, it is necessary to standardize existing spraying technique for LDHP molecules. Thus, to standardize the existing spraying technique with two LDHP molecules (bispyribac-Na and clodinafop + metsulfuron), a field experiment was conducted for two years (2016-18) in rice during Kharif season and wheat Rabi season. The post-emergence (PoE) application of LDHP molecules, viz. bispyribac-Na at 25 g/ha in rice and clodinafop + metsulfuron at 60 + 4 g/ha in wheat were tested with flat fan (FF) and floodjet (FJ) nozzles using spraying volume of 250 and 500 l/ha. The weed control efficiency (WCE) obtained with different spray volume and nozzles usage was on par. The maximum WCE of 76% in rice and 89% in wheat was observed. A spray volume of 250 l/ha with either FF or FJ nozzle effectively controls the weeds and increases the field capacity by 60-100%.

Herbicide-resistance, Phalaris minor, Physiology, Weed management, Wheat

Weeds are a major constraint of wheat productivity improvement in India. Among the major weeds, Phalaris minor Retz. is the most problematic weed that mimics wheat. Herbicides are mostly used by farmers to manage weeds in wheat and dependency on single herbicide or herbicides with same mode of action resulted in the development of multiple herbicide-resistance in P. minor. A field study was conducted at CCS Haryana Agricultural University, Hisar during 2016-17 and 2019-20 with an objective to study the growth and physiological response of wheat and management of herbicide-resistant P. minor with selective herbicides in wheat. The sequential application of tank-mix (TM) pre-emergence application (PE) of pendimethalin + pyroxasulfone (1500 + 102 g/ha) or pendimethalin + metribuzin (1000 + 175 g/ha) followed by post-emergence application (PoE) of pinoxaden 60 g/ha or mesosulfuron + iodosulfuron 14.4 g/ha resulted in complete control of herbicide- resistant P. minor and other broad-leaved weeds (BLW). The better control of weeds resulted in higher wheat leaf area index (LAI) and crop growth rate (CGR) with 43-46% higher wheat grain yield over the weedy check. However, 0-9% visual toxicity on the crop was observed in metribuzin-associated treatments, which was nullified with the advancement of crop stage. The maximum marginal benefit was observed in weed-free check (39,192 /ha) closely followed by pendimethalin + pyroxasulfone (TM) PE fb mesosulfuron + iodosulfuron PoE, while marginal benefit-cost ratio (MBCR) was highest with mesosulfuron + iodosulfuron (17.8) PoE followed by pinoxaden + metribuzin (50+150 g/ha) PoE. It was concluded that sequential application of PE followed by PoE herbicide with a rotational application of herbicides having different mode of action is suitable for management of herbicide-resistant  P. minor in wheat. 

Conservation agriculture, Residue retention, Greengram, Weed control efficiency, Nutrient use efficiency, Water productivity 

There has been a growing trend for achieving sustainable crop intensification without jeopardizing land productivity through conservation agriculture (CA). The CA has paved the way for cultivation of pulses in diverse cropping systems. A field experiment was conducted at ICAR-Indian Agricultural Research Institute, New Delhi during 2018-19 and 2019-20 cropping cycle with summer greengram in maize-wheat system to assess the effects of CA on weed interference, crop productivity and resource use efficiency. Results showed that CA-based practices with residue retention resulted in a considerable reduction in weed density and biomass when compared to conventional tillage (CT). Greengram yield parameters in CA were higher than in CT. The permanent broad bed (PBB) with residue retention (R) and recommended 100% N application (100N) (~PBB+R+100N) gave ~56% higher greengram grain yield than CT with considerably higher water productivity, nutrient-use efficiency and net returns. The adoption of CA practice involving PBB+R in greengram led to higher weed control efficiency and was more productive, remunerative and irrigation water-use efficient. Thus, it could potentially boost up the greengram productivity, profitability and resource-use efficiency under maize-wheat-greengram system in north-western Indo-Gangetic Plains (IGP) of India.

Conservation agriculture, Conventional tillage, Integrated weed management, Weed phyto-sociology, Zero tillage

The understanding of the diverse weed flora composition and weed shift in conservation agriculture production system is important to identify weed management component to increase agro-ecosystem sustainability. Hence, in this study, different tillage and weed management practices were assessed to evaluate their impact on diverse weed flora composition and shift in maize-wheat cropping system in North Western Himalaya from 2018-20 in an ongoing long-term experiment being conducted since 2013. Fifteen treatment combinations comprising of five tillage treatments, viz. conventional tillage (CT) in maize-CT in wheat; CT-zero tillage (ZT); ZT-ZT; ZT-zero tillage in combination with residue retention (ZTR) and ZTR-ZTR and three weed management treatments, viz. recommended herbicide (H) in maize-recommended herbicide (H) in wheat; integrated weed management (IWM)-IWM and hand weeding (HW)-HW were evaluated in a strip plot design. In CT, annual weed species were dominant, whereas, perennial weeds dominated in zero tillage (ZT). A shift in weed species with greater dominance of monocots and a marginal decrease in dicots was observed. Parthenium hysterophorus, an obnoxious weed, was observed in the experimental field in maize only during 2018. The monocot weed (Echinochloa colona) had higher relative density (RD), relative abundance (RA), relative frequency (RF) and important value index (IVI) compared to the dicot weeds in maize crop. In Rabi (winter) season, Avena ludoviciana (monocot grass) had higher RD, RF and IVI values, while, Daucus carota (perennial weed) had higher RA when compared to the other annual and biennial weeds. The grain yield of main and intercrop and system productivity were higher in conservation agriculture-based production systems in combination with recommended herbicide (ZTR+H-ZTR+H) in maize-wheat based cropping systems.

Blackgram, Bio-efficacy, Clodinafop-propargyl, Economics, Sodium acifluorfen, Weed management

The efficacy of a post-emergence herbicides in managing weeds in blackgram was evaluated during summer and rainy (Kharif) seasons of 2016 at University of Agricultural Sciences (UAS), GKVK, Bangalore, India. The experiments were laid in RCBD with three replications comprising of nine treatments. Major weed species observed were: Cyperus rotundus, Eleuisine indica, Dactyloctenium aegyptium, Borreria articularis, Echinochloa colona, Commelina benghalensis, Euphorbia geniculata, Phyllanthus niruri. The post-emergence application (PoE) of sodium acifluorfen 16.5% + clodinafop-propargyl 8% EC (206.25 + 100 g/ha) has attained significantly higher seed and haulm yield of blackgram (1305 and 2088 kg/ha, respectively) in summer 2016 and (1519 and 2253 kg/ha, respectively) in Kharif  2016, followed by sodium acifluorfen 16.5% + clodinafop-propargyl 8% EC (165 + 80 and 123.75 + 60 g/ha) (1192 and 1808 kg/ha, respectively) in summer 2016 and (1425 and 2095 kg/ha, respectively) in Kharif 2016. Similarly the weed control efficiency in summer and kharif 2016 was higher with sodium acifluorfen + clodinafop-propargyl (330 + 160 g/ha) PoE (93.20 and 91.0%, respectively) and it was followed by sodium acifluorfen + clodinafop-propargyl (206.25 + 100 g/ha) PoE (89.51 and 90.24%, respectively) when compared to weedy check. The increased yield was mainly due to a significant reduction in weed density and biomass, without any phytotoxicity to succeeding finger millet crop under semi-arid Alfisols. 

Chickpea, Economics, Fomesafen + fluazifop-p-butyl, Herbicides, Imazethapyr, Imazethapyr + imazamox, Weed control efficiency

A filed experiment was conducted at Mahatma Gandhi Chitrakoot Gramodaya Vishwavidyalaya, Chitrakoot, Satna, Madhya Pradesh during winter  (Rabi) season of 2019-20 and 2020-21 to assess the efficacy of herbicides on production and profitability of chickpea (Cicer arietinum L.). The experiment was laid out in a randomized block design with ten treatments and three replications. The crop was sown as per the package of practices recommended for zone Kymore Plateau of Madhya Pradesh. The major monocot weed was Cynodon dactylon and dominant dicot weed was Chenopodium album at 30 days after sowing (DAS). At 30 DAS, significantly lower weed density (7.75/m2) and biomass (2.70 g/m2) were recorded with post-emergence application (PoE) of fomesafen (11.1% W/W) 220 g + fluazifop-p-butyl (11.1% W/W) 220 g/ha PoE at 20 DAS, followed by imazethapyr (35%) + imazamox (35%) 100 g/ha PoE at 20 DAS. The lowest weed index was noted with imazethapyr 55 g/ha PoE followed by pre-emergence application (PE) of pendimethalin 0.75 kg/ha and fomesafen 220 g + fluazifop-p-butyl 220 g/ha PoE at 30 DAS. Higher weed control efficiency (WCE) at 30 DAS was recorded with fomesafen 220 g + fluazifop-p-butyl 220 g/ha (70.6%) followed by hand weeding at 20 and 40 DAS (57.1%). However, fomesafen 220 g + fluazifop-p-butyl 220 g/ha PoE at 20 DAS and imazethapyr + imazamox 100 g/ha PoE at 20 DAS caused severe injury to chickpea plants and even mortality of a few plants. Significantly higher 1000 seed weight (183.0 g) and grain yield (1.79 t/ha) were observed with imazethapyr 55      g/ha PoE which was statistically at par with weed free check. Significantly higher net returns ( 70746/ha) and B:C ratio (3.97) were recorded with imazethapyr 55 g/ha PoE ( 70746/ha), followed by pendimethalin 0.75 kg/ha PE. The monetary efficiency ( 589.5/ha/day) of imazethapyr 55 g/ha PoE was statistically at par with weed free ( 541.3/ha/day) and was significantly higher than all other treatments.

Black polythene mulch, Mulching, Raised bed system, Stem training, Tomato, Weed control efficiency 

A field experiment was conducted at the Research Farm of Vegetable Science, DR YSPUHF, Nauni, Solan (HP), India to evaluate the effect of polythene mulches, planting methods and training systems on weed control and yield response of tomato crop. The experiment was laid out in factorial randomized block design with twelve treatments and replicated thrice. The consortium effect of raised bed (RB) + black polythene mulch (BPM) + two stem training have recorded less weed density (142.00/m2), greater weed control efficiency (64.64%), less fresh (82.00 g/m2) and dry weed biomass (13.00 g/m2) and higher yield (100.12 t/ha). The dominance of Cyperus rotundus, Echinochloa crus-galli and Galinsoga parviflora weed species was also less with the integration of raised bed, black polythene mulch and two stem training system. This practice helps in the tomato production with better water conservation; weed management and improved tomato yield under mid-hill conditions of Himachal Pradesh.

Lantana camara, Dyeing, Fabric, UV protection, Weed utilization

Herbal extract application on textile substrates is in great demand around the globe. In this study, a natural dye extracted from Lantana camara L. leaves' extract was tested to assess the ultra-violet protective properties on cotton fabric using direct dip dyeing technique. Extraction of phytochemicals was carried out using ethanol and aqueous solvents. Total phenolic content (TPC) quantification revealed that TPC of L. camara leaves' extracts were highest in ethanolic extraction as compared to aqueous extracts. The ultra violet protection factor (UVF) values ranged between good to excellent for the cotton fabrics. A cotton fabric treated in a solution containing cross linking agent showed a shade of light yellowish green. The colour fastness against light, washing, rubbing and perspiration of cotton fabric treated in extracted dye solution as well as treated with citric acid as cross-linking agent showed good to very good colour fastness properties (4–5). The results confirmed that natural dye from Lantana camara extract have potential for application in fabric dyeing and also helpful in producing UV protective fabric.

Atrazine, Maize establishment, Rice straw mulch, Tembotrione, Weed management 

A field experiment was conducted during rainy (Kharif) season of 2019 at N.E.B. Crop Research Centre of GBPUA&T, Pantnagar with an objective to identify the best establishment method and weed management treatment for maize to attain higher maize growth, yield and economic returns. The experiment was conducted in split-plot design with three replications comprising of three establishment methods as main plot factor and seven weed management treatments as sub-plot factor, replicated thrice. Among the establishment methods, raised bed system was found most effective in reducing weed growth. The highest weed control efficiency of 85.7% was recorded with pre-emergence application (PE) of atrazine 1000 g/ha fb post-emergence application (PoE) of tembotrione 120 g/ha which was followed by rice straw mulch 5 t/ha fb tembotrione 120 g/ha PoE and tembotrione 120 g/ha PoE alone. Raised bed system resulted in 8.0% higher maize grain yield over zero till system and highest net return and B:C ratio. Among the weed management treatments, highest maize grain yield, net return and B:C ratio were recorded with atrazine 1000 g/ha PE fb tembotrione 120 g/ha PoE. 

Hand weeding, Herbicides, Soybean, Sodium-acifluorfen + clodinafop-propargyl, Weed management

A field experiment was conducted at Agricultural Research Station, Ummedganj, Kota, Rajasthan during rainy (Kharif) season, 2019 to study the comparative efficacy of pre- and post-emergence herbicides in managing weeds and improving productivity of soybean (Glycine max L. Merrill). The experimental field was infested with grassy weeds (48.60%), broad-leaved weeds (39.49%) and sedges (11.91%). Cynodon dactylon (L.) Pers., Eleusine indica (L.) Gaertn., Echinochloa crus-galli (L.) Beauv and Echinochloa colona (L.) Link among grassy weeds, Boerhavia diffusa L. nom. cons., Convolvulus arvensis L., Commelina benghalensis L., Digera arvensis Forsk., Celosia argentea L. among broad-leaved weeds and Cyperus rotundus L., the sedge were major associated weeds. Maximum soybean seed yield (1800 kg/ha) and higher weed control efficiency (77.79%) were recorded with hand weeding twice at 20 and 40 days after sowing (DAS) followed by post-emergence application of sodium-acifluorfen 16.5% + clodinafop- propargyl 8% (premix) 165 + 80 g/ha (1550 kg/ha).

Blackgram, Fluazifop-p-butyl, Imazethapyr, Pendimethalin, Propaquizafop, Weed management 

A field study was conducted at Research Station in Kota, Rajasthan during rainy (Kharif) season of 2020 to identify suitable herbicides including pre-emergence (PE) and post-emergence herbicides (PoE) for managing weeds and improve productivity of blackgram [Vigna mungo (L.) Hepper]. Among weed control treatments tested, the lowest weed density, weed index and highest crop growths parameters like plant population, plant height, dry matter accumulation, nodules/plant, dry weight of nodules was recorded with hand weeding twice at 20 and 40 days after sowing (DAS), pre-emergence application (PE) of pendimethalin 1.0 kg/ha followed by (fb) post-emergence application (PoE) of propaquizafop 2.5% w/w 33.3 g/ha + imazethapyr 3.75% w/w (pre-mix) ME 50 g/ha at 20 DAS and pendimethalin 1.0 kg/ha PE fb fomesafen 11.1% w/w 220 g/ha + fluazifop-p-butyl 11.1% w/w 220 g/ha (pre-mix) PoE at 20 DAS. 

Hand weeding, Inter-cultivation, Oxadiargyl, Mustard, Weed management 

A field experiment was conducted on sandy loam soils to identify alternate weed management treatments to economically manage weeds and improve mustard growth and yield of mustard. Among tested weed management treatments, higher growth parameters, higher yield attributes (number of siliquae/plants and seeds/siliquae) and yield of mustard were observed under inter-cultivation and hand weeding twice at 15 and 30 days after seeding (DAS) which was at par with pre-emergence application (PE) of oxadiargyl 0.09 kg/ha fb inter-cultivation at 30 DAS.

Allelopathy, Andrographis paniculata,  Plectranthus amboinicus, Tagetes minuta, Weed management

Several plants express the allelopathic phenomenon through release of allelochemicals. Plants rich in allelochemicals can be used for controlling weeds in organic crop production. Current study was aimed at screening of Andrographis paniculata (Burm.f.) Nees (bitter weed), Plectranthus amboinicus (Lour) Spreng (Indian borage) and Tagetes minuta L.(Southern cone marigold) for allelopathic potential against upland weeds.This study was conducted from February to May 2021 in the Department of Agronomy, College of Agriculture, Vellanikkara, Kerala Agricultural University, Thrissur. The methanol extracts of Tagetes minuta and Andrographis paniculate at 25-30% concentration as pre-emergence application exhibited allelopathic effect on broad-leavedweeds. 

Duckweed, Fertilization rates, Nutrient removal efficiency, Wolffia globosa 

Aquatic vegetation like duckweed (Wolffia globosa) can eliminate contaminant from wastewater, which also can be commercial and possible options for wastewater treatment. Thus, this study aimed to estimate the nutrient removal capability of Wolffia globosa under artificial culture conditions. The nutrient removal capacity of W. globosa was evaluated in a 12-day growth trial with mineral mixture containing 173.6 mg/litre nitrogen; 40.3 mg/litre phosphorous; 100 mg/litre potassium and 0.6 g/litre as a reference fertilization rate (RF) along with five other different [RF/2; RF/4; RF/8; RF/16; RF/20 and Control (no fertilizers)] NPK fertilization rates under natural sunlight. In all the treatments, the concentrations of nitrate-nitrite, ammonia, nitrate and ortho-phosphate, decreased over the experimental period in a statistically significant (p=0.05) manner. At the end of the experiment, the total dissolved inorganic nitrogen (T-DIN) in the culture media was reduced by 99. 57% (RF/20), 100% (Control group - no fertilizers) while Ortho-phosphate (OP) by 100% in RF/16, RF/20 and control group, respectively. It was concluded that the Wolffia globosa is a suitable aquatic plant for nutrient removal under natural sunlight.