Herbicides, Maize, Tembotrione, Weed flora, Yield

A field experiment was conducted at the Norman E. Borlaug Crop Research Center, Pantnagar, during the rainy seasons of 2009 and 2010  to evaluate the efficacy of tembotrione (42% SC), a new post-emergence herbicide against mixed flora in maize as well as its residual effect on growth and yield of the succeeding mustard crop. The experimental field was highly infested with Echinochloa colona, Digitaria sanguinalis and Cyperus rotundus. Post emergence application of tembotrione 120 g/ha along with surfactant was found most effective to control the grassy as well as non-grassy weeds as compared to other herbicidal treatments either applied as pre or post emergence. This treatment also recorded highest grain yield during both the years which was at par with a lower dose (110 g/ha + surfactant) or even pre emergence application of the herbicide. Addition of surfactant (1000 ml/ha) increased the kernel yield significantly and reduced the density of weeds effectively as compared to the application of tembotrione without surfactant. No residual effects were observed on the growth and yield of succeeding mustard crop.

Berseem, Cuscuta, Herbicides, Interference, Lucerne, Pendimethalin

Field dodder (Cuscuta campestris), the most damaging annual obligate stem parasite is a serious problem in forage legumes lucerne (Medicago sativa L.) and Egyptian clover (Trifolium alexandrinum L.). Studies were conducted to investigate the interference of C. campestris densities in lucerne and the efficacy of herbicides for its control in lucerne and Egyptian clover. Even at Cuscuta density of 0.25 plants/m2 (1 plant/4m2) caused detrimental effect on lucerne seed yield (85.5-95.3% loss). A high dose of pendimethalin (1000 g/ha) applied pre-emergence reduced Cuscuta emergence but was phytotoxic to lucerne as compared to lower doses and application at 14 days after sowing (DAS). Application of imazethapyr 100 g/ha and pendimethalin 750 g/ha at 14 DAS significantly improved green fodder yield of lucerne but failed to control Cuscuta infestation at reproductive stage resulting in poor seed yield. Method of seeding did not influence the population and green fodder yield of Egyptian clover and Cuscuta emergence. Post-emergence (at 14 DAS) application of pendimethalin 500-750 g/ha effectively controlled Cuscuta campestris in Egyptian clover and produced the maximum green fodder and seed yields.

Atrazine, Herbicide combinations, Maize, Pendimethalin, Weeds

Twelve treatments involving tank-mix combinations of atrazine and pendimethalin as pre-emergence followed by (fb) post emergence application of 2,4-D and metsulfuron methyl along with hand weeding twice (20 and 40 DAS) and untreated check were tested in maize during 2009 and 2010 at Palampur. Echinochloa colona, Panicum dichotomiflorum, Cyperus iria, Commelina benghalensis, Ageratum conyzoides, Digitaria sanguinalis and Polygonum alatum were the dominant weeds. Pendimethalin 1.50 kg/ha, atrazine fb atrazine 0.75 kg/ha, atrazine 0.75/1.0 +  pendimethalin 0.75/0.50 fb metsulfuron methyl 4 g/ha effectively controlled Echinochloa colona. Atrazine fb atrazine brought about significant reduction in the count of  Panicum dichotomiflorum up to 60 DAS. Pendimethalin fb atrazine, atrazine 1.0 + pendimethalin 0.50 fb 2, 4-D 0.75 kg/ha and hand weeding twice effectively reduced the population of Commelina up to 60 DAS. Pendimethalin/atrazine fb atrazine and atrazine + pendimethalin fb 2,4-D/metsulfuron-methyl controlled  Ageratum conyzoides up to 60 DAS. Pendimethalin/atrazine fb atrazine, atrazine + pendimethalin fb metsulfuron-methyl/2, 4-D and pendimethalin significantly reduced total weed dry weight. Atrazine 1.0 + pendimethalin 0.50 kg/ha (post) and atrazine 0.75 + pendimethalin 0.75 kg/ha fb 2, 4-D gave significantly higher grain yield and net returns. Weeds reduced maize grain yield by 50.3%.

Benefit : cost ratio, Economics, Hand weeding, Herbicides, Solanum melongena, Yield

The present investigation was conducted to evaluate the effect of weed management practices on weeds as well as crop growth and yield parameters of brinjal along with the economics of weed management during winter season of 2009-10 at the Department of Horticulture, Indira Gandhi Krishi Vishwavidyalaya, Raipur. It was observed that the weed Parthenium hysterophorus dominated the experimental field. All the weed management treatments significantly reduced the dry matter of weeds and increased fruit yield of the crop significantly over unweeded check. Among the treatments, pendimethalin (Extra) (0.64 kg/ha) pre-transplanting + one hand weeding at 40 DAT + pendimethalin (Extra) (0.64 kg/ha) at 45 DAT as post-emergence resulted in better performance followed by pendimethalin (1.0 kg/ha) pre-transplanting + one hand weeding at 45 DAT with respect to growth and yield parameters due to effective weed management in brinjal. Maximum benefit: cost ratio was also obtained with pendimethalin (extra) (0.64 kg/ha) pre-transplanting + one hand weeding at 40 DAT + pendimethalin (Extra) (0.64 kg/ha) at 45 DAT.

Diversification and intensification, Production efficiency, Rice-based cropping systems,Weed dynamics

Field experiments were conducted during 2007-08 and 2008-09 to study weed dynamics and production efficiency under diversified and intensified rice based cropping systems in Kymore Plateau and Satpura Hills Zone of Madhya Pradesh. Among the all 12 rice based cropping systems under Kharif, in rice Echinochloa crusgalli was the most dominating weed contributing 32.8% of total weed intensity at most critical period (25 DAT) while Monochoria vaginalis at harvest stage (18.8%). During Rabi, relative density of weeds varied between different crops. In early (30.2 to 43.3%) and at harvest stage (10.1 to 46.8%) Medicago denticulata was found to be more serious weed almost in all Rabi crops grown under different cropping systems but in onion and garlic Portulaca oleracea having higher intensity at harvest stage (45.2%). The Portulaca spp. predominantly infested to all summer crops at early (41.5 to 54.6%) and harvest stage (37.2 to 44.1%). In rice varieties the weed intensity and biomass ranged from 229.0 to 254.2/m2 and 1.0 to 1.15 t/ha under different crop systems respectively. During Rabi, weed intensity was higher in vegetable pea (207.3/m2) and weed biomass was higher berseem (0.71 t/ha). During summer season, the weed intensity was maximum (156.4/m2) in okra which resulted into the highest weed biomass production (0.67 t/ha). Both rice and wheat crops grown under rice–wheat system require large quantity of irrigation water which is favourable to build up a typical weed infestation problem. All diversified and intensified cropping systems significantly led to record higher production efficiency (83.13kg/ha/day to 57.05kg/ha/day) beneficial to minimize the serious challenges posed by the weeds as compared to both existing cropping systems viz., rice-wheat (45.63kg/ha/day) and rice-chickpea (39.49kg/ha/day).

Intercropping, Maize+blackgram, Weed management

Field experiments were conducted to study the effect on weeds and crop yield under maize + blackgram intercropping system at Raipur during 2004 and 2005. Treatments consisted of five planting geometry viz., sole maize, sole blackgram, maize +blackgram (1:1), maize + blackgram (2:1) and maize + blackgram (2:2) and four weed management practices viz., weedy check, hand weeding (HW)  at 30 DAS, alachlor  2.0 kg/ha as pre-emergence and alachlor  1.5 kg/ha as pre-emergence + HW at 40 DAS. Grain yield, productivity rating index (PRI), production efficiency (PE) and weed-control efficiency (WCE) were the highest under maize + blackgram (2:1) for maize. However, weed smothering efficiency of maize was highest under maize + blackgram (1:1). At harvest of blackgram (75 DAS) and maize (105 DAS), the dry weight of weeds were the lowest with alachlor  1.5 kg/ha + HW at 40 DAS. This treatment produced maximum grain yield, PRI and PE of maize and blackgram.

Direct-seeded rice, Dry matter accumulation, Herbicides, Seed yield, Weed control

Field experiments were conducted during Kharif season of 2007 and 2008 at Punjab Agricultural University, Ludhiana to evolve suitable combination of pre and post-emergence herbicides for effective weed management in direct-seeded rice under unpuddled conditions. Results indicated that during 2007, integration of post-emergence application (30 Days after sowing) of bispyribac (25 and 30 g/ha) or azimsulfuron (20 g/ha) with pre-emergence application of pendimethalin 0.75 kg/ha, pretilachlor 0.5 kg/ha and thiobencarb 1.25 kg/ha provided effective control of weeds and produced significantly higher grain yields than unweeded (control) treatment. During 2008 also, integration of pre-emergence application of pendimethalin 0.75 kg/ha or oxadiargyl 0.90 g/ha with post-emergence application of bispyribac 25 kg/ha, azimsulfuron 20 g/ha and 2,4-D 0.5 kg/ha resulted in significant reduction in dry matter of weeds and increased grain yield as compared to alone application of pendimethalin 0.75 kg/ha. Pre-emergence application of flufenacet 80 g/ha and early post-emergence application of penoxsulam 30 and 35/g ha were found ineffective for controlling weeds.

2,4-D, Cono weeding, Metsulfuron-methyl, Rice, Sesbania aculeata, Weed management 

Field experiments were conducted during 2004-06 at Agricultural Research Station, Mannuthy, Thrissur, Kerala to find out the effect of concurrent growing of dhaincha (Sesbania aculeata) and its methods of incorporation on weed management in wet seeded rice. Sowing of rice and dhaincha was done in alternate rows using the rice-cum-green manure seeder.  Treatments consisted of incorporation of dhaincha at 20 and 30 days after sowing (DAS) by using cono weeder, spraying 2, 4-D 1.0 kg/ha, and metsulfuron- methyl 5 .0 g/ha.  Two levels of N (100 and 75% of recommended dose of 90 kg N/ha) were superimposed. Rice alone with 5 t/ha FYM and recommended dose of 90-45-45 kg N-P-K/ha was taken as control. Concurrent growing of dhaincha and its incorporation at 30 DAS resulted in a weed suppression of 70% with an yield enhancement to the tune of 0.840 t/ha and increased profitability of   12520/ha). Application of 2,4–D resulted in maximum reduction of weeds without any adverse effect on rice. Nitrogen at different levels had no significant influence of weed incidence.

Economics, Forest pastures rehabilitation, Grubbing, Glyphosate, Lantana camara, Manual cutting, Perennial grasses

A study on rejuvenation of  wild sage (Lantana camara L.) infested forest pastures in Shivalik foot-hills of Jammu & Kashmir  was conducted from April 2006 to December 2008. The study included manual cuttings of Lantana bushes; manual cuttings followed by   application of 1% glyphosate on its regenerated growth of 30 cm in height; and manual grubbings. These were followed by either no plantation of grasses, planting  either of hybrid napier and  Setaria cuttings. Results of the study revealed that the fresh bio-mass of Lantana bushes  recorded  a sizeable reduction ranging from 66 to 99% under different treatments over its initial average fresh bio-mass  value of 28 kg/25 m2. Likewise, a significant reduction in the number of Lantana bushes per unit area to the extent of 67-99% over its initial average value of 6 bushes/25 m2 was also recorded with grubbing and the herbicide applied treatments. Application of glyphosate 30 cm regenerated growth of Lantana bushes and grubbing treatments followed by planting either of  hybrid napier and Setaria  were found equally effective  in rehabilitation of Lantana infested forest pastures as both of these grasses provided good soil cover and recorded higher  forage yields under these treatments i.e. hybrid napier 1.81 to 2.07 t/ha and Setaria 0.98 to1.02 t/ha.These two treatments were also found significantly superior to the repeated Lantana cutting treatments and  decreased  fresh Lantana bio-mass by 94.20 to 99.03% over its initial bio-mass value. However, between these two most effective treatments  i.e. the management of Lantana bushes with the application of glyphosate followed by planting of  either hybrid napier and Setaria  grasses were found economically superior, with a net saving of rupees 6,640/ha, over the grubbings of Lantana followed by planting either of these grasses .

Crop-weed competition, Echinochloa colona, Grain yield, Rice

In order to assess the impact of varying densities of jungle rice (Echinochloa colona) on rice, a field experiment was conducted at Directorate of Weed Science Research, Jabalpur farm in Kharif  2005 and 2006. With increasing population density of E. colona from 50 to 400 plants/m2, there was a significant reduction in LAI, biomass production as well as grain yield of rice due to competition from weed plants for growth factors like light, nutrients and space etc. The reduction in dry matter was to the tune of 32% with a E. colona density of 400 plants/m2 as compared to pure rice crop. Though the chlorophyll content of rice decreased with increasing density of E. colona but it maintained a higher chlorophyll content than E. colona. The increasing densities of E. colona significantly decreased various yield attributes of rice with the effect being more drastic on effective tillers/m2. The reduction in grain yield varied from 48 to 86% as the density of E. colona increased from 50 to 400 plants/m2.

Cuscuta, Imazethapyr, Lucerne, Pendimethalin, Weed density, Weed dry weight

A field experiment was conducted to study the effect of integrated weed management practices on forage quality in lucerne (Medicago sativa L.) during 2008-09. The treatments consisted of salt (10%) treatment to seeds of lucerne + hand weeding at 30 DAS and after each cut, salt (10%) treatment to seeds + imazethapyr 75 g/ha at 12 DAS, salt (10%) treatment to seeds + pendimethalin 0.5 kg/ha at 12 DAS, stale seed bed + hand weeding at 30 DAS, pendimethalin 0.5 kg and 0.75 kg/ha as PE, imazethapyr 75 g and 100 g/ha at 12 DAS, pure seed of lucerne + hand weeding at 30 DAS and after each cut, hand weeding at 30 DAS and after each cut (farmers practice), weedy check and weed free check. experiment was laid in RBD with three replications. The results indicated that the density and dry weight of weeds (excluding cuscuta) were significantly lower with weed free check. Higher weed control efficiency and green fodder yield of lucerne at each cut and total was significantly higher with application of imazethapyr  75 g/ha at 12 DAS and was at par with selection of pure seed + hand weeding at 30 DAS and after each cut. Cuscuta control efficiency was maximum with application of pendimethalin and imazethapyr and their combination with salt treatment (10%) to seed and selection of pure seed of lucerne + hand weeding at 30 DAS and after each cut.

Age of seedlings, B:C ratio, Butachlor, Cono-weeding, Grain yield, SRI 

Planting of 10 or 15 days old seedlings did not differed significantly on grain yield of rice. Among weed management practices SRI method of  planting with four times cono-weeding at 10 days interval starting from 10 days after transplanting recorded significantly higher grain yield (6003 kg/ha) and was found effective in weed control. However, pre-emergence application of butachlor + one hand weeding at 20 DAT was equally effective alternative weed control in SRI method of cultivation. 

Avena ludoviciana, Crop-weed competition, Phalaris minor, Wheat

Field experiments were conducted in microplots to study the effect of N supply on competition between wheat and two prominent grassy weeds viz., Phalaris minor and Avena ludoviciana. Six treatments comprising three species combinations (wheat monoculture, weed monoculture, wheat and weed mixture in equal proportions) and two levels of N fertilization (20 and 120 kg/ha) were studied in a factorial randomized block design with four replications. Results revealed that total dry weight of wheat was significantly lower in mixture than in monoculture. Wheat was more competitive than P. minor at high N, but less competitive at low N.  A. ludoviciana, was more competitive than crop at both N levels. Wheat reduced photosynthesis of weeds to a greater extent as compared to pure weed population. A. ludoviciana exhibited higher values of Pn as compared to P. minor at both N levels in both stand (monoculture and mixture) types. Leaf area index and leaf chlorophyll content of both wheat and weed were at par in mixture at high N and in monoculture at low N, indicating a higher competitiveness (for nitrogen) of A. ludoviciana.

Chemical control, Pre-emergence herbicides, Tapioca, Weed control efficiency

Tapioca (Manihot esculenta Crantz) is a high carbohydrate tropical tuber crop relished for its taste by the people of Kerala. Both the method of planting adopted and growth habit of cassava gives opportunities for luxurious weed growth during the initial stage of the crop and hence the crop is prone to weed competition during the first 2-3 months after planting. The present study was carried out with the objective of identifying a good pre emergence herbicide for tapioca as a labour saving and cheaper option. Diuron was the most effective herbicide as evidenced by the lowest weed dry matter production and highest weed control efficiency (WCE). This was not found a good herbicide in tapioca intercropped with legume either for green manure or grain purpose due to the 100% mortality of the green gram.  In legume intercropped tapioca, fluchloralin  0.75 kg/ha resulted in good weed control with a cost saving of 60% over hand weeding.  In a pure tapioca crop the herbicide Diuron 2 kg/ha resulted in excellent weed control with least cost.  A saving of 86% in costs was effected compared to manual weeding.

Bioassay, Leaching, Pendimethalin, PVC columns

A laboratory column experiment was conducted to study the leaching behaviour of pendimethalin in sandy clay soil of Madhya Pradesh. Soil sample (0-15cm) was packed in PVC columns and conditioned by adding water one day before the herbicide application. Pendimethalin was added directly to column after dilution with 10 ml water at recommended dose (1.0 kg/ha) and double the recommended dose (2.0 kg/ha). Water was added every day to encourage movement of herbicide. After seven days, the column was split vertically into two halves. The herbicide activity was determined at different depths through bioassay by using maize as sensitive plant. The growth of maize due to pendimethalin was affected in the upper layer of soil up to 5 cm at recommended dose (1.0 kg/ha) and up to 10 cm  at double the recommended dose. This reveals that pendimethalin does not leach below 10 cm in soil even at double the recommended dose.

Crop and weeds, Mixed winter crop, Phytosociology, Weed flora

Floristic study and variation in frequency, density and basal cover of crop and weeds were studied at bimonthly intervals in a mixed wheat and mustard crop at Gujar lake margin in district Jaunpur (Uttar Pradesh). The total number of weed species recorded on 28th December, 2008 and 27th February, 2009 were 34 and 37, respectively. Maximum number of weeds was of Poaceae and followed by Asteraceae. Cynodon dactylon was the most dominated weed. The maximum frequency (65 and 72%), density (54.19 and 99.80/m2) and basal cover (1.084 and 2.994 cm2/m2) were of Cynodon dactylon followed by Cyperus rotundus. It was mainly due to their vegetative mode of propagation and by their competitive ability in the favourable soil moisture, texture and nutrients conditions.

Cropped fields, Non-cropped fields, Weed flora

The cultivated area of upland is having serious problem of weed infestation which declines the yield of upland crops. Some weeds spread fast in this region because of favourable environment in crops, forest plantation and natural forest. Weed dominated blocks namely Bakawand, Batar, Tokapal, Lohandiguda and Jagdalpur selecting 7 villages from each block of Bastar district during August-September and February-March, 2008 under national Agricultural Innovative Project. In all the blocks, Spilanthes acmella, Celosia argentia and Digitaria adscendens were the most dominant weeds in upland cropping. Among these weeds, Sphaeranthes indicus (17.65, 15.14, 22.41, 15.00 and 11.40% in Bakawand, Bastar, Tokapal, Lohandiguda and Jagdalpur, respectively) was most dominant weeds followed by Chenopodium album (14.12, 12.96, 17.14, 20.00 and 14.81% in respective blocks) and Digitaria adscendens (12.94, 12.04, 15.52, 15.00 and 7.41% in Bakawand, Bastar, Tokapal, Lohandiguda and Jagdalpur, respectively). Chromalaena odorata (20.54, 23.33, 17.93, 22.73 and 17.27 in Bakawand, Bastar, Tokapal, Lohandiguda and Jagdalpur, respectively) and Hyptis suaveolens L. (22.32, 25.36, 19.31, 25.31 and 19.09% in respective blocks) were higher in arresting relative density in respective blocks.

Chemical control, Herbicide, Sorghum

A field experiment was conducted during rainy season of 2009 at the Directorate of Sorghum Research, Hyderabad to evaluate the efficacy of new herbicide molecules in grain sorghum. The experimental field was dominated with broad-leaved weeds (66.6%) followed by grasses (27.8%) and sedges (5.6%). Infestation of weeds caused 50% reduction in grain yield of sorghum. Application of oxyfluorefen as pre-emergence, and metsulfuron methyl, carfentrazone, atlantis (mesosulfuron+idosulfuron), almix (chlorimuron+metsulfuron) and total (sulfosulfuron +metsulfuron) as post-emergence caused mild to severe phytotoxicity on grain sorghum resulting in poor yields. This showed that newly developed post-emergence herbicides recommended in other grain crops are not safe for sorghum and therefore, screening of more number of new herbicides is required.