DESC:FIELD OF THE INVENTION
The present invention relates to a herbicidal composition. More particularly, the present invention relates to a synergistic herbicidal composition comprising Paraquat dichloride and Oxyfluorfen.
BACKGROUND OF THE INVENTION
Herbicides have a phytotoxic effect on plants, and so they are used in plant protection for controlling weeds or totally inhibiting their growth. Herbicides can be non-selective, which means that they destroy all growth, or selective in part or full, whereby they can be used for inhibiting the growth of weeds of only certain crop plants.
However, single herbicides typically lack the weed control spectrum, e.g., the range of weed species effectively controlled by the herbicide, to fully control the diversity of weeds in a field. Therefore, it is common to apply two or more herbicides simultaneously in order to achieve the desired spectrum of control. To facilitate the simultaneous application of two or more herbicides, it is common to package the different herbicides separately as concentrate formulations, which can be admixed with water in a spray tank by the end user, a method also known as 6tank-mixing. More conveniently, however, the different herbicides can be co-formulated in a single concentrate formulation, requiring only dilution in water by the end user prior to application by spraying. Such a formulation is often known as a package-mix.
Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant hormones. Herbicides used to clear waste ground, industrial sites, railways and railway embankments are non-selective and kill all plant material with which they come into contact. Further, applying combinations of two or more herbicides simultaneously to a field may be necessary or desired for synergistic effects other than an increased control spectrum. For example, some herbicides have prolonged visual symptomology, that is, it takes a relatively long period of time (i.e., up to two weeks or more) for susceptible plants to show the visual effects of treatment. Generally, such extended periods without any visual indication of herbicidal effectiveness detract from the commercial value of a herbicidal product. Therefore, it is often beneficial to combine two or more herbicides in a tank mix or a package-mix that will provide for more rapid burn down and earlier visual symptomology, thus improving the value of the overall herbicidal product.
Package-mix formulations present numerous challenges to the formulator of agricultural chemicals such as herbicides. For example, the formulation should contain the herbicidal active ingredients at as high a total concentration as possible, for maximum convenience to the end user and to minimize packaging and shipping costs, while keeping the active ingredients within the desired weight ratios with respect to each other. Most importantly, the package-mix formulation must exhibit sufficient physical and chemical stability to have an effective shelf life of at least a few months, preferably at least a year, and ideally at least two years.
In some cases, herbicidal active ingredients have been shown to be more effective in combination than when applied individually and this is referred to as "synergism." As described in the Herbicide Handbook of the Weed Science Society of America, Eighth Edition, 2002, p. 462 "'synergism' [is] an interaction of two or more factors such that the effect when combined is greater than the predicted effect based on the response to each factor applied separately." The present invention is based on the discovery that Oxyfluorfen and Paraquat or its salts, already known individually for their herbicidal efficacy, display a synergistic effect when applied in combination.
This invention relates to improved Paraquat herbicidal compositions. Paraquat (1,1'-dimethyl-4,4'-bipyridinium) and its salts are well-known nonselective herbicides active against both annual and perennial weeds. It kills a wide range of annual grasses and broad-leaved weeds and the tips of established perennial weeds and is used for both large scale agricultural applications and also for home and garden type applications.
However, Paraquat herbicides lack activity in soil and selectivity in plants. Paraquat herbicides are also relatively not very effective against some weeds such as ryegrass (Lolium rigidum). This mainly happens due to either repeated use or Paraquat seems to be inactivated, possibly by tight binding as in soil, before reaching the site of action in chloroplasts. Thus, the grower is frequently prone to use repeated applications of the herbicide where only one application is necessary because they have failed to see any change in the weeds or undesired vegetation within the first few days or week. To counter this problem often, other herbicides are mixed with Paraquat, or selective herbicides are used later in the growing crop.
In view of the above, obtaining an herbicidal composition which demonstrates no cross-resistance to existing Paraquat and overcome its disadvantages is extremely difficult. Thus, it is an object of this invention to provide a herbicidal composition which demonstrates a high controlling effect along with reduced crop production cost and reduced environmental load. Accordingly, the invention provides a herbicidal composition comprising Paraquat or its salts in combination with diphenyl ether type of herbicides such as e.g. Oxyfluorfen, essentially in order to delay the inactivity of Paraquat and to improve weed control spectrum (Please confirm).
Paraquat dichloride is the common name for 1,1'-dimethyl-4,4'-bipyridinium. Its herbicidal activity is described in The Pesticide Manual, Seventeenth Edition, 2015 at entry no. 607. Paraquat dichloride is a quaternary ammonium herbicide having following structure.

Paraquat dichloride is a compound with reported herbicidal activity against range of annual grasses and broad-leaved weeds and the tips of established perennial weeds. It is known that it belongs to the bipyridylium group of herbicides which is an oxidant that interferes with electron transfer, a process that is common to all life. Addition of one electron gives the radical cation: MV may represent any chemical species.
[MV]2+ + e- ? [MV]+
The radical cation is also susceptible to further reduction to the neutral [MV]0
[MV]+ + e- ? [MV]0
As an herbicide, Paraquat dichloride acts by inhibiting photosynthesis. In light-exposed plants, it accepts electrons from photosystem I (more specifically Fd, which is presented with electrons from PS I) and transfers them to molecular oxygen. In this manner, destructive reactive oxygen species are produced. In forming these reactive oxygen species, the oxidized form of Paraquat dichloride is regenerated, and is again available to shunt electrons from photosystem I to restart the cycle.
Paraquat dichloride is often used to catalyze the formation of reactive oxygen species (ROS), more specifically, the superoxide free radical. Paraquat dichloride will undergo redox cycling in vivo, being reduced by an electron donor such as NADPH, before being oxidized by an electron receptor such as dioxygen to produce superoxide, a major ROS.
Paraquat dichloride is generally available in the market in soluble (liquid) concentrate soluble liquid form with 24% w/w Paraquat dichloride content. Available combinations with Paraquat dichloride in the art are with diuron and diquat. Paraquat dichloride can also be tank mixed preferentially with compounds like Triazine herbicides like atrazine, metribuzin etc.
Oxyfluorfen is 2-chloro-?,?,?-trifluoro-p-tolyl 3-ethoxy-4-nitrophenyl ether. Technical Oxyfluorfen is a red to yellow solid having a melting point of 65-84 °C. Oxyfluorfen is a selective herbicide applied by pre-emergence or post-emergence applications to cotton, onions, peanuts, soybeans, sugarcane, trees and vegetables, controlling monocotyledonous and broad-leaved weeds. Oxyfluorfen belongs to diphenyl ether family of herbicides having following structure formula

EP 0448538 A1 and EP 0394211 A1, disclose a process for the preparation of a solid formulation comprising N-(phosphonomethyl)glycine (glyphosate) or a water-soluble salt thereof and Oxyfluorfen. According to EP 0448538 a liquid premix comprising Oxyfluorfen, at least one surfactant, and water or solvents is prepared at a temperature of from 50 °C. to 80 °C., thus dissolving Oxyfluorfen, and a second premix comprising N-(phosphonomethyl)glycine or a water soluble salt thereof, an acid acceptor if appropriate and preground ammonium sulfate is formed, and both premixes are combined to form an extrudable composition, which is extruded and optionally dried. Oxyfluorfen can also be tank mixed preferentially with the following acetolactate synthase (ALS) mode of action products for improved weed control: amidosulfuron, azimsulfuron, bensulfuron- methyl, bispyribac-sodium, cinosulfuron, cloransulam-methyl, chlorimuron-ethyl, chlorsulfuron, cinosulfuron, cyclosulfamuron, diclosulam, ethametsulfuron-methyl, ethoxysulfuron, flazasulfuron, florasulam, flucarbazone-sodium, flucetosulfuron, flumetsulam, flupyrsulfuron-methyl,-sodium, halosulfuron-methyl, imazamethabenz-methyl, imazamox, imazapic, imazapyr, imazaquin, imazethapyr, imazosulfuron, mesosulfuron- methyl, metazosulfuron, metsulfuron-methyl, nicosulfuron, orthosulfamuron, oxasulfuron, primisulfuron, procarbazone-sodium, propoxycarbazone, propyrisulfuron, prosulfuron, pyriftalid, pyrazosulfuron-ethyl, pyribenzoxim, pyriminobac-methyl, pyroxsulam, pyrimisulfan, rimsulfuron, sulfometuron-methyl, triasulfuron, tribenuron-methyl, triflusulfuron-methyl and tritosulfuron.
There is a further need in the art to provide synergistic herbicide compositions as they afford various advantages. Herbicide combinations offer advantages of improved weed control, a greater spectrum of weeds controlled, reduced cost and reduced residue problems.
Hitherto, no attempts have been made to formulate a combination of Paraquat dichloride and Oxyfluorfen. Therefore, there is a long felt need in the art to provide a stable formulation comprising Paraquat dichloride and Oxyfluorfen that solves the problems mentioned above and solves the existing problem of phytotoxicity induced by these active ingredients.
The present invention provides a storage stable agrochemical formulation of Paraquat dichloride and Oxyfluorfen in the form of soluble (liquid) concentrate (SL) (does SL also represents soluble concentrate?); suspension concentrate (SC) and dry flowable (DF) that causes no phytotoxicity.
SUMMARY OF THE INVENTION
In accordance with an embodiment of the invention, there is provided a synergistic herbicidal composition, comprising; (a) Paraquat dichloride; (b) Oxyfluorfen; and (c) additives.
Preferably, the mass ratio of Paraquat dichloride to Oxyfluorfen in the above composition ranges from 1.33:1 to 10:1. Further, Paraquat dichloride is preferably present in an amount of 24%, and Oxyfluorfen is present in amounts ranging from 2.4 to 18.0%.
The synergistic herbicidal composition of the present invention may be formulated as a soluble (liquid) concentrate soluble concentrate or liquid (SL), suspension concentrate (SC) or dry flowable (DF), and more preferably as a soluble (liquid) concentrate soluble concentrate or liquid (SL).
The synergistic herbicidal composition, comprises additives selected from the group consisting of a solvent, an emulsifier, an anti-freezing agent, a defoamer, a biocide, and water, and wherein the composition is in the form of a soluble (liquid) concentrate soluble concentrate (SL).
The synergistic herbicidal composition of the present invention, comprises: solvent in an amount of 1 to 15%, and preferably 15%; the emulsifier is present in an amount of 0.1 to 10%, and preferably 3%, the anti-freezing agent is present in an amount of 1.00 to 5.00%, and preferably 2.00%, defoamer is present in an amount of 0.01 to 0.50%, and the biocide is present in an amount of 0.01 to 0.50%.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1. is a flowchart for preparing a synergistic herbicidal composition in the form of a soluble (liquid) concentrate soluble concentrate (SL).
DETAILED DESCRIPTION OF THE INVENTION
The invention according to its various aspects is particularly pointed out and distinctly claimed in the appended claims read in view of this specification and appropriate equivalents.
It is to be noted, as used in the specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a composition containing “a compound includes a mixture of two or more compounds. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. The expression of various quantities in the terms of “% w/w” and “%” means the percentage by weight, relative to the weight of the total composition unless otherwise specified.
As used herein WP formulation, WDG formulation, SL formulation, SC formulation and EC formulation are the international denominations adopted by the FAO (Food and Agriculture Organization of the United Nations) to designate wettable powder, water dispersible granules, soluble (liquid) concentrate soluble liquid or concentrate, suspension concentrate and emulsifiable concentrate, respectively. (Does SL represent soluble concentrate or soluble liquid or do they mean the same thing? Accordingly, kindly make changes throughout the disclosure)
The term "agro chemically effective amount" is that quantity of active agent, applied in any amount which will provide the required control of broad leaved weeds and grasses. The particular amount is dependent upon many factors including, for example, the crop, weeds sought to be controlled and environmental conditions. The selection of the proper quantity of active agent to be applied, however, is within the expertise of one skilled in the art.
Many newer and conventional molecules are in practice in agriculture crops for different weed management, but the indiscriminate use of these chemicals resulted in reduced percent control due to build-up of the resistance in targeted weed population. There are many reports on resistance of different weeds for different molecules mainly due to either resistance or inactivity due to different reasons. To overcome these problems grower is frequently prone to use repeated applications of the herbicide where only one application is necessary. Other option is to either mix other herbicides as readymade formulation or use different herbicides in sequence. Second option is more costly as well as not environmental friendly as it requires repeated application and thereby increases the environmental load.
To counter this problem, the present investigation relates to an herbicidal composition comprising Paraquat dichloride and Oxyfluorfen as active ingredients present in a synergistic ratio for an efficacious weed control and the methods of preparing the same.
Accordingly, the inventors of the present invention have formulated a synergistic herbicidal composition, comprising Paraquat dichloride, Oxyfluorfen, and additives wherein the mass ratio of Paraquat dichloride to Oxyfluorfen is in the range from 1.33:1 to 10:1 and wherein the composition comprises Paraquat dichloride in an amount of about 24% and wherein Oxyfluorfen is present in amounts ranging from 2.4 to 18%.
The synergistic herbicidal composition may be in the form of a soluble (liquid) concentrate soluble concentrate or liquid (SL), and comprises additives such as a solvent, an emulsifier, an anti-freezing agent, a defoamer, a biocide, and water. Like other aqueous liquid formulations, soluble (liquid) concentrate soluble concentrates are easy to handle and measure, dust free, non-flammable and offer good miscibility with water.
Suitable solvents useful in accordance with the invention are cyclohexanone, N-methyl pyrollidone, butanol, dimethyl sulfoxide and combinations thereof, and present in an amount in the range from 1 to 15%, and preferably 15%.
It is desirable to have an emulsifier in the synergistic herbicidal composition. An emulsifier is a substance that stabilizes an emulsion by increasing its kinetic stability. One class of emulsifiers are known as "surface active agents", or surfactants. Non-limiting examples of emulsifiers that can be used in the present invention include nonionic and anionic surfactants. Each of these surfactants can be used either singly or in combination and present in an amount in the range from 0.1 to 10%, and preferably 3%.
An anti-freezing agent is generally added to herbicidal compositions, to prevent the aqueous compositions from freezing. Suitable anti-freezing agents useful herein, but not limited to, include propylene glycol, di-ethylene glycol (DEG), mono ethylene glycol (MEG) and combinations thereof. Preferably, the anti-freezing agent is present in an amount in the range from 1.00 to 5.00%, and more preferably 2%.
A defoamer, also called as anti-foam, is generally added to an herbicidal composition as foam formation prevents the efficient filling of a container. Preferably, the defoamer is dimethyl polysiloxane emulsion and present in an amount in the range from 0.01 to 0.50%.
The synergistic herbicidal composition comprises a biocide selected from the group consisting of Proxel GXL, formaldehyde and combinations thereof, and preferably present in an amount in the range from 0.01-0.50%. Proxel GXL is a broad spectrum biocide for the preservation of industrial water-based products, such as the composition of the present invention, against spoilage from bacteria, yeasts and fungi.
The present invention is more particularly described in the following examples that are intented as illustrations only, since numerous modifications and variations within the scope of the present invention will be apparent to those of skill in the art. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are on a weight basis and all reagent used in the example were obtained or are available from the chemical suppliers.
EXAMPLES
The following examples illustrate the basic methodology and versatility of the present invention.
Examples 1-4
The unit of each value below is “% w/w” i. e. the percentage by weight, relative to the weight of the total solution or composition unless otherwise specified. The compositions contemplated by each of the Examples 1-4 that are tabulated in Table 1 are formulated as a soluble (liquid) concentrate soluble concentrate (SL, Does SL represents soluble concentrate?)) formulation.
Table 1: Synergistic herbicidal compositions
Component Function Examples
1 2 3 4
Paraquat Dichloride **A.I 24.00 24.00 24.00 24.00
Oxyfluorfen **A.I 2.40 5.00 12.00 18.00
Cyclohexanone Solvent 15.00 15.00 15.00 15.00
Blend of Anionic & Non-ionic surfactants Emulsifier 3.00 3.00 3.00 3.00
Di-ethylene glycol Antifreeze agent 2.00 2.00 2.00 2.00
Dimethyl polysiloxane emulsion Deformer 0.01 0.01 0.01 0.01
Proxel GXL Biocide 0.01 0.01 0.01 0.01
Demineralized Water Solvent *q.s. *q.s. *q.s. *q.s.
**A.I.= Active Ingredient
*q.s.= quantity Suffucient
The aforementioned herbicidal composition can be formulated as soluble (liquid) concentrate soluble concentrate (SL) by a process described below.
Process for preparing synergistic herbicidal composition in the form of soluble (liquid) concentrate soluble concentrate (SL)
The herbicidal compositions of Examples 1-4 are prepared by the process described hereinafter and represented by a flowchart in figure 1. Entries for Paraquat dichloride and Oxyfluorfen in table 2 differ from those in table 1 as entries in table 1 are for 100% pure compounds, whereas those in table 2 are for technical ones, i.e. those containing a certain percentage of impurities.
The amounts of active ingredients presented in table 2 may be greater than the values calculated taking into account the percentage purity of the active ingredients, to compensate for losses of said ingredients during the manufacturing process. It was observed that following said procedure on industrial scale the final yield of A.I. will be similar or same as to standardized values.
All the raw materials are verified for conformance to the laid down individual specifications. The required quantities of raw materials, as illustrated in Table 2 below were weighed, and transferred through the auto-batching system. Oxyfluorfen Technical is first dissolved in solvent and then emulsifier is added and mixed by high shear mixer in a mixing vessel to make a homogeneous emulsion.
De-mineralized (D.M.) water along with Paraquat dichloride technical, anti-freezing agent, deformer, and biocide are added and mixed to make homogeneous mass. After homogeneous mixing, the quality of in-process sample is checked for conformance to the laid out specifications. The quality approved in-process sample is transferred to the holding tank after passing through sparkler filter pump for packing as per the requirements.

Table 2: Quantities of the *TGAI and raw materials charged
Component Function Quantities of materials charged (kg)
1 2 3 4
Paraquat Dichloride (based on 42% w/w minimum purity) *TGAI 57.15 57.15 57.15 57.15
Oxyfluorfen (based on 95% w/w minimum purity) *TGAI 2.53 5.27 12.64 18.95
Cyclohexanone Solvent 15.00 15.00 15.00 15.00
Blend of Anionic & Nonionic surfactants Emulsifier 3.00 3.00 3.00 3.00
Di-ethylene glycol Antifreeze agent 2.00 2.00 2.00 2.00
Dimethyl polysiloxane emulsion Deformer 0.01 0.01 0.01 0.01
Proxel GXL Biocide 0.01 0.01 0.01 0.01
Demineralized Water Solvent 20.30 17.56 10.19 3.88
*TGAI. = Technical grade active ingredient
Evaluation of the synergistic effect for herbicidal composition comprising Paraquat dichloride and Oxyfluorfen
The performance of the herbicidal composition of the present invention (Paraquat dichloride and Oxyfluorfen) was compared against the known compositions of Paraquat dichloride 24% SL (WILQUAT) and Oxyfluorfen 23.5% EC (OXYGUARD), which were evaluated against weed spectrum in Tea and also the vigor/yield of the crop was tested. Area for experiment was marked for different plot sizes and application was made using high volume knapsack sprayer at 2-4 leaf stage of weeds. Experimental design was in randomized blocks with five replication and each plot measured 50 sq. m (10 x 5 m). Observations on weed population, dry weight and weed control efficiency (WCE%) were made 30 days after application (DAA).
Table 3 below summarizes the synergistic effect that exists whenever the action of an active ingredient combination is greater than the sum of the actions of the individual components i.e. Paraquat dichloride and Oxyfluorfen against different weed spectrum at different concentrations.
In the field of agriculture, it is often understood that the term "synergy" is as defined by Colby S. R. in an article entitled "Calculation of the synergistic and antagonistic responses of herbicide combinations" published in the journal Weeds, 1967, 15, p. 20-22. The action expected for a given combination of two active components can be calculated as follows:

Where,
E = Expected percentage of herbicidal control for the combination of the two herbicides at defined doses (for example equal to x and y respectively),
X = X is the percentage of herbicidal control observed by the compound (I) at a defined dose (equal to x),
Y = Y is the percentage of herbicidal control observed by the compound (II) at a defined dose (equal to y),
When the percentage of herbicidal control observed for the combination is greater than the expected percentage, there is a synergistic effect.

Table 3: Synergistic impact of separate and combined treatments for narrow leaved (monocot) and broad leaved (dicot) weed spectrum at different concentrations of synergistic inseticidal composition comprising Paraquat dichloride and Oxyfluorfen
Compound (g or mL)/ha WCE (%)at 30 DAA* Expected Control (Et) Colby’s Ratio (Ea+b/Et)
Paraquat dichloride 960 Ea = 53.87 - -
Oxyfluorfen 96 Eb1 = 16.33 - -
Oxyfluorfen 200 Eb2 = 46.26 - -
Oxyfluorfen 480 Eb3 = 49.58 - -
Oxyfluorfen 720 Eb4 = 51.67 - -
Paraquat dichloride and Oxyfluorfen 960 + 96 Ea+b1 = 68.73 61.40 1.119
Paraquat dichloride and Oxyfluorfen 960 + 200 Ea+b2 = 93.27 75.20 1.240
Paraquat dichloride and Oxyfluorfen 960 + 480 Ea+b3 = 93.09 76.74 1.213
Paraquat dichloride and Oxyfluorfen 960 + 720 Ea+b4 = 92.67 77.70 1.192
DAA = Days after application
Ea = % WCE after 30 DAA for Paraquat dichloride
Eb = % WCE after 30 DAA for Oxyfluorfen
Ea+b = % WCE after 30 DAA for Paraquat dichloride and Oxyfluorfen
Et = Expected %WCE after 30 DAA for Paraquat dichloride and Oxyfluorfen in combination (Calculated)
(What is the unit for active ingredient in A.I/ha, is it g, kg, or mg)
It can be seen from the data presented in Table 3, combination of Paraquat dichloride and Oxyfluorfen at all the doses demonstrate synergistic effect against different weed population.

Bio-efficacy of herbicidal composition comprising Paraquat dichloride and Oxyfluorfen against overall weed spectrum in tea crop
Field trials were performed to evaluate the biological efficacy of the herbicidal combination of present invention (Paraquat dichloride and Oxyfluorfen) against the overall weed spectrum in the field at various trial sites. This evaluation was performed by comparing the claimed herbicidal combination in the present specification against the marketed reference products, i.e., Paraquat Dichloride 24% SL (WILQUAT), Oxyfluorfen 23.5% EC (OXYGUARD) and Glyphosate 71% SG (WILLOSATE 71).
Area for experiment was marked for different plot sizes and application was made using high volume knapsack sprayer at 2-4 leaf stage of weeds. Based on various doses, weighed quantity of test products were dissolved in 5 L of water/treatment and sprayed uniformly. Experimental design was in randomized blocks with five replications and each plot measured 50 sq. m (10 x 5 m). Observation on weed population, dry weight and weed control efficiency (WCE %) was assessed at 15, 30 and 45 days after application.
Weed Control Efficiency (%) = [(Weed Dry Weight in Control Plot – Weed Dry Weight in Treated Plot)/ Weed Dry Weight in Control Plot] x 100

Details of Experiment
Target weeds: Overall weed spectrum
Crop: Tea
Application Method: high volume knapsack sprayer fitted with flat fan nozzle
The treatment details are tabulated in Table 4 below.

Table 4: Treatment details for evaluation of bio-efficacy of herbicidal composition against weed spectra in tea crop
Particular Treatment Dose /Acre Time of Application
T1 Paraquat dichloride 24% and Oxyfluorfen 2.4% SL 1600 mL 2-4 leaf stage of weeds
T2 Paraquat dichloride 24% and Oxyfluorfen 5% SL 1600 mL
T3 Paraquat dichloride 24% and Oxyfluorfen 12% SL 1600 mL
T4 Paraquat dichloride 24% and Oxyfluorfen 18% SL 1600 mL
T5 Paraquat dichloride 24% SL 1600 mL
T6 Oxyfluorfen 23.5% EC 400 mL
T7 Glyphosate 71% SG 1200 g
T8 Hand Weeding @ 15 & 30 DAS -- --
T9 Control (Water Spray) -- --

The bio-efficacy of different treatment schedules and yield data of tea crop is summarized in Table 5 and 6 below.

Table 5: Effect of herbicidal compositions on total weed count (no./m2), total weed dry weight/biomass (g/m2) and Weed Control Efficacy (WCE) (%) in tea crop
No. Treatments Dose per acre Weed Population (no./m2) Total Weed Dry Weight (g/m2) Weed Control Efficacy (WCE) (%)
15 DAA* 30 DAA* 45 DAA* 15 DAA* 30 DAA* 45 DAA* 15 DAA* 30 DAA* 45 DAA*
1 T1 1600 mL 45.67
(6.79) 49.00
(7.04) 53.33
(7.34) 61.00
(7.84) 65.33
(8.11) 68.67
(8.32) 65.54 64.62 64.96
2 T2 1600 mL 15.33
(3.98) 19.00
(4.42) 22.00
(4.74) 15.00
(3.94) 14.67
(3.89) 17.33
(4.22) 91.53 92.06 91.16
3 T3 1600 mL 16.00
(4.06) 20.67
(4.60) 24.33
(4.98) 15.67
(4.02) 16.00
(4.06) 18.33
(4.32) 91.15 91.34 90.65
4 T4 1600 mL 18.00
(4.30) 24.33
(4.98) 27.67
(5.31) 18.33
(4.34) 19.33
(4.45) 22.00
(4.74) 89.64 89.53 88.78
5 T5 1600 mL 49.67
(7.08) 62.67
(7.95) 78.00
(8.86) 63.67
(8.01) 75.67
(8.73) 86.33
(9.32) 64.03 59.02 55.95
6 T6 400 mL 61.33
(7.86) 79.00
(8.92) 87.33
(9.37) 76.00
(8.75) 94.33
(9.74) 99.00
(9.97) 57.06 48.92 49.49
7 T7 1200 g 59.67
(7.76) 80.33
(8.99) 89.33
(9.48) 72.67
(8.55) 98.67
(9.96) 109.33
(10.48) 58.94 46.57 44.22
8 T8 -- 13.33
(3.72) 12.67
(3.63) 54.00
(7.38) 25.33
(5.08) 24.00
(4.95) 78.33
(8.88) 85.69 87.00 60.04
9 T9 -- 156.00
(12.51) 165.00
(12.86) 176.33
(13.30) 177.00
(13.32) 184.67
(13.61) 196
(14.02) - - -
SEm ± -- 1.75 1.77 1.78 1.76 1.87 2.15
CD 5% NS 5.20 5.30 5.35 5.25 5.60 6.25
* DAA: Days after application; SEm ±: Standard Errors of Means; CD 5%: Critical Difference; g = Gram; m2 = Square meter; mL = Millilitre;
* Value in Parentheses is v(x+0.5) transformed value.

Table 6: Treatment wise yield data of green tea leaves
Treatment Green Leaf Yield (q/ha)*
T1 6.65
T2 7.56
T3 7.41
T4 7.38
T5 5.60
T6 5.26
T7 5.48
T8 5.98
T9 3.20
SEm ± 0.66
CD 5% 1.96
*SEm ±: Standard Errors of Means; CD 5%: Critical Difference; (q/ha)* = quintal/hectare
Data presented in table 5 and 6 shows that weed population was significantly affected by all the treatments compared to control when observed at 15, 30 and 45 days after application (DAA). At 45 DAA Paraquat dichloride 24% and Oxyfluorfen 5% SL formulation @ 1600 mL recorded lowest weed population closely followed by T3 and T4 at equal doses. Similar results were observed in case of weed dry weight and WCE, wherein highest WCE of 91.16% was observed in plots treated with Paraquat dichloride 24% and Oxyfluorfen 5% SL formulation at 45 DAA. Highest green leaf yield of tea was recorded on treatment with Paraquat dichloride 24% and Oxyfluorfen 5% SL in the dose of 1600 mL/acre; i.e. 7.56 q/ha, which was statistically significant over all other treatments. It was thus concluded that the Paraquat dichloride 24% and Oxyfluorfen 5% SL formulation at 1600 mL/acre was the best combination dose over all other tested dose of Paraquat dichloride and Oxyfluorfen to control weed flora in tea and to obtain better yield attributes.
Phytotoxic effect of herbicidal composition comprising Paraquat dichloride and Oxyfluorfen on tea crop
Visual observations on phytotoxicity were recorded for leaf injury on tip/surface, Epinasty/Hyponasty, and wilting, etc. on 0-10 scale (Table 7) at 1, 3, 7, 14 and 21 days after each application and then average was taken. The results are presented in table 8.
Table 7. Phytotoxicity visual scoring 0-10
Score Phytotoxicity (Percent)
0 No phytotoxicity
1 1 – 10
2 11 – 20
3 21 – 30
4 31 – 40
5 41 – 50
6 51 – 60
7 61 – 70
8 71 – 80
9 & 10 Complete destruction
Table 8: Phytotoxicity of herbicidal composition on tea crop
No. Treatments Dose (mL/acre) Phytotoxicity (Days after Application)
1 3 7 14 21
1 Paraquat dichloride 24% and Oxyfluorfen 5% SL 1600 0 0 0 0 0
2 3200 0 0 0 0 0
3 Paraquat dichloride 24% and Oxyfluorfen 12% SL 1600 0 0 0 0 0
4 3200 3 1 0 0 0
5 Paraquat dichloride 24% and Oxyfluorfen 18% SL 1600 2 1 0 0 0
6 3200 4 2 0 0 0
7 Control - 0 0 0 0 0
0= No Phytoxicity
Table 8 above shows that Paraquat dichloride 24% and Oxyfluorfen 5% SL formulation did not show any phytotoxicity @ 1600 ml/acre and 3200 ml/acre. In case of Paraquat dichloride 24% and Oxyfluorfen 12% SL @ 3200 ml/acre and Paraquat dichloride 24% and Oxyfluorfen 18% SL 1600 ml and 3200 ml/acre, slight phytotoxicyty was observed at 1 and 3 DAA which decreased over time.
From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present investigation. It is to be understood that no limitations with respect to the specific embodiment illustrated is intended or should be inferred. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.

CLAIMS:
We claim:
1. A synergistic herbicidal composition, comprising; (a) Paraquat dichloride; (b) Oxyfluorfen; and (c) additives.
2. The synergistic herbicidal composition, as claimed in claim 1, wherein the mass ratio of Paraquat dichloride to Oxyfluorfen is in the range from 1.33:1 to 10:1.
3. The synergistic herbicidal composition, as claimed in claims 1 and 2, wherein Paraquat dichloride is present in an amount of 24%, and wherein Oxyfluorfen is present in amounts ranging from 2.4 to 18.0%.
4. The synergistic herbicidal composition, as claimed in claims 1 to 3 wherein the composition may be in the form of a soluble (liquid) concentrate (SL), suspension concentrate (SC) or dry flowable (DF).
5. The synergistic herbicidal composition, as claimed in claims 1 to 4, wherein the additives are selected from the group consisting of a solvent, an emulsifier, an anti-freezing agent, a defoamer, a biocide, and water, and wherein the composition is in the form of a soluble (liquid) concentrate (SL).
6. The synergistic herbicidal composition, as claimed in claim 5, wherein the solvent is selected from the group consisting of cyclohexanone, N-methyl pyrollidone, butanol, dimethyl sulfoxide and combinations thereof, and present in an amount in the range from 1 to 15%, and preferably 15%.
7. The synergistic herbicidal composition, as claimed in claim 5, wherein the emulsifier is selected from the group consisting of a non-ionic surfactant, anionic surfactant and combinations thereof, and present in an amount in the range from 0.1 to 10%, and preferably 3%.
8. The synergistic herbicidal composition as claimed in claim 5, wherein the anti-freezing agent is selected from the group consisting of propylene glycol, DEG, MEG and combinations thereof, and present in an amount in the range from 1.00 to 5.00%, and preferably 2.00%.
9. The synergistic herbicidal composition as claimed in claim 5, wherein the defoamer is dimethyl polysiloxane emulsion and present in an amount in the range from 0.01 to 0.50%.
10. The synergistic herbicidal composition as claimed in claim 5, wherein the biocide is selected from the group consisting of Proxel GXL, formaldehyde and combinations thereof and present in an amount in the range from 0.01 to 0.50%.
11. The synergistic herbicidal composition, as claimed in any of the claims 1 to 10, wherein the composition is non-phytotoxic.