DESC:FIELD OF THE INVENTION
The present invention relates to herbicidal composition and more particularly to a synergistic herbicidal composition comprising glyphosateGlyphosate and paraquatParaquat dichloride.
BACKGROUND OF THE INVENTION
It is observed very often, that prolonged usage of herbicides leads to development of resistance in weeds which make the herbicides ineffective. This results in application of herbicidal compositions in higher doses which is detrimental to the environment.
A significant obstacle faced by the researchers in this technical field is regarding herbicidal activity. For increasing crop yield it is vital that biological activity of the herbicides should not only be improved but also persistent over a period of time.
Hence, there is a need to develop a herbicidal composition which addresses the problem of resistance and soil toxicity and also is used at reduced dosages, controls environmental damage, offers broader weed control spectrum, improved and healthy foliage, rainfastedness, improved crop yield, saves labour, improves plant growth and is yet cost-effective to the end user.
This invention relates to improved liquid formulation comprising of glyphosateGlyphosate-type herbicide and paraquatParaquat-type herbicide. GlyphosateGlyphosate and its salts are well-known broad spectrum herbicides active against both annual and perennial weeds. The herbicidal activity of this class of herbicide was first reported by D. D. Baird et al. (Proc. North Cent. Weed Control Conference, 1971, 26, 64). This class of herbicide is especially known for its non-selective herbicidal effectiveness against grasses and is used for both large scale agricultural applications and also for home and garden type applications.
GlyphosateGlyphosate is the common name for N-(phosphonomethyl)glycine (Molecular Formula: C3H8NO5P, Molecular Weight: 169.1) was first described in US3799756 US3799758(Please confirm) by Monsanto. The structure, as depicted in the FAO Manual, is as follows:

Its herbicidal activity is described in The Pesticide Manual, Seventeenth Edition, 2015 on entry no. 427. The synthesis and/or use of glyphosateGlyphosate-type herbicides are described in U.S. Patents Nos. 3,799,758; 3,835,000; 3,868,407; 3,950,402; 4,083,893 (Please confirm); 4,147,719 and European Patent Application No. 19,384. U.S. Patent No. 3,929,450 teaches that the herbicidal effectiveness of N-(phosphonomethyl)glycines can be increased by applying them with certain N-phosphonic acids. An extensive review of GlyphosateGlyphosate and related Chemistry is set forth by J. E. Franz in IUPAC-Advances in Pesticide Chemistry; Gassbuhler Ed. (1978-Zurich). Farm Chemicals Handbook (1982) at page C-254 teaches that the isopropylamine salt of glyphosateGlyphosate may be tank mixed with Lasso atrazine, Princep , Lorox , Lexone and Sencor for use in certain minimum tillage systems. It has also been suggested to tank-mix trifluralin (i.e., ?,?,?-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) with the isopropylamine salt of glyphosateGlyphosate. The words "Lasso", "Princep" and "Lorox" are trade marks.
GlyphosateGlyphosate herbicide is normally used as a form of a water soluble salt, preferably the isopropylamine salt, sodium salt or ammonium salt, of glyphosateGlyphosate. Liquid and solid formulations intended to be diluted or dissolved in a spray tank by a farmer, generally contain in addition to the glyphosateGlyphosate salt, a surfactant or a surfactant mixture which increases the biological effectiveness of the glyphosateGlyphosate herbicide. GlyphosateGlyphosate controls wide range of annual and perennial grasses and broad leaved weeds, at pre-emergence, post-emergence and pre-harvest in cereals, peas, beans, oilseeds, orchards, forestry, home garden and industrial weed control.
GlyphosateGlyphosate herbicides are relatively slow acting especially against certain difficult to kill weed and grass species, such as Bermuda grass and some other glyphosateGlyphosate resistant weeds like Conyza canadiensis, Hedyotis verticillata, Eleusine indica, Lolium multiflorum, Amaranthus spp., Echinocloa colona etc. to name a few. Thus, the common purchaser is frequently prone to use repeated applications of the herbicide including glyphosateGlyphosate and other herbicides 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. This problem is even more accentuated because the glyphosateGlyphosates act more effectively against mature plants than against young plants and most plantations, orchards and garden weed clean-up is done in the early growing season and hence against young plants.
ParaquatParaquat dichloride is the common name for 1,1'-dimethyl-4,4'-bipyridinium chloride. Its herbicidal activity is described in The Pesticide Manual, Seventeenth Edition, 2015 at entry no. 607. ParaquatParaquat dichloride is a quaternary ammonium herbicide having following structure.

ParaquatParaquat 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] represents a chemical species.
[MV]2+ + e- ? [MV]+(Please define MVRepresentation for cation)
The radical cation is also susceptible to further reduction to the neutral [MV]0
[MV]+ + e- ? [MV]0
As an herbicide, paraquatParaquat 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 paraquatParaquat dichloride is regenerated, and is again available to shunt electrons from photosystem I to restart the cycle.
ParaquatParaquat dichloride is often used to catalyze the formation of reactive oxygen species (ROS), more specifically, the superoxide free radical. ParaquatParaquat 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.
ParaquatParaquat dichloride is generally available in the market in soluble liquid form with 24% w/w ParaquatParaquat dichloride content. For agriculture application paraquatParaquat herbicides suffer the disadvantage that they lack activity in soil and their lack of selectivity in plants. ParaquatParaquat herbicides are also relatively not very effective against some weeds such as ryegrass (Lolium rigidum). This mainly happens due to either repeated use or paraquatParaquat dichloride 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 paraquatParaquat dichloride, or selective herbicides are used later in the growing crop. Available combinations with paraquatParaquat dichloride in the art are with diuron and diquat. ParaquatParaquat dichloride can also be tank mixed preferentially with compounds like Triazine herbicides like atrazine, metribuzin etc.
In view of the above, obtaining an herbicidal composition which overcomes disadvantages mentioned above and demonstrates no cross-resistance to existing paraquatParaquat dichloride is extremely difficult.
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 glyphosateGlyphosate and paraquatParaquat dichloride. Therefore, there is a long felt need in the art to provide a stable formulation comprising glyphosateGlyphosate and paraquatParaquat dichloride that solves the problems mentioned above and solves the existing problem of phytotoxicity induced by these active ingredients. 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 glyphosateGlyphosate and paraquatParaquat dichloride or their salts in combination thereof and a method for preparing the same.
The present invention provides such a storage stable agrochemical soluble concentrate (SL); suspension concentrate (SC) and Soluble Granules (SG) of glyphosateGlyphosate and paraquatParaquat dichloride or their salts that causes no phytotoxicity.
SUMMARY OF THE INVENTION
The present invention relates to a synergistic herbicidal composition for wide spectrum control of weeds, delaying the emergence of the resistant strains of weeds, minimizing the risk of development of resistance, and achieving effective and economical control of undesired weeds.
In accordance with an embodiment of the invention, there is provided a synergistic herbicidal composition, comprising GlyphosateGlyphosate and ParaquatParaquat dichloride; wherein the mass ratio between GlyphosateGlyphosate, and ParaquatParaquat dichloride ranges from 1:5 to 8:1 and preferably is 2.73:1..(Range not supported by examplesPossible range is given whereas in examples we have only given preferred range))
In accordance with yet another embodiment of the invention, GlyphosateGlyphosate is present in an amount of 5 to 50% and ParaquatParaquat dichloride is present in an amount in the range from 2 to 25%.(Possible range is given whereas in examples we have only given preferred rangeRange not supported by examples)
In accordance with a further embodiment of the invention, the synergistic herbicidal composition of the present invention may be in the form of a suspension concentrate (SC), soluble granules (SG), or soluble liquid (SL).
In accordance with another embodiment of the invention, the synergistic herbicidal composition further comprises additives selected from the group consisting of anti-freezing agent, dispersing cum wetting agent, defoamer, biocide, thickener, water and combinations thereof, and the composition is in the from of a suspension concentrate (SC).
In accordance with still another embodiment of the invention, the anti-freezing agent is present in an amount in the range from 1.00-8.00%, the dispersing cum wetting agent is present in an amount in the range from 2.00-10.00%, the defoamer is present in an amount in the range from 0.01-0.50%, the biocide is present in an amount in the range from 0.01-0.50% and the thickener is present in an amount in the range from 0.10-0.50%.
In accordance with still yet another embodiment of the invention, said composition is non-phytotoxic.
The synergistic herbicidal composition of the present invention is found to be useful in controlling a wide range of weeds. The composition achieves improved biological performance in single application by enhancing overall control of weeds over a shorter period of time. Additional benefits of using the herbicidal composition of the present invention includes reduced risk of occupational exposure and hazards, lower cost of application, better cost-benefit ratio to the end users, reduced fuel cost and labor cost, savings in applicator’s time and reduced wear of personal protection equipment and losses caused by mechanical damage to the crops and soil.

BRIEF DESCRIPTION OF DRAWINGS
Figure 1. is a flowchart for preparing a synergistic herbicidal composition in the form of a suspension concentrate (SC).

DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a novel, stable and synergistic herbicidal combination. The novel combination of the present invention comprises combination of glyphosateGlyphosate and paraquatParaquat dichloride along with other additives.
The term "agrochemically effective amount" is that quantity of active agent, applied in any amount which will provide the required control of weeds. The particular amount is dependent upon many factors including, for example, the crop and 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.
It is to be noted, as used in the specification and 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” or “%” means the percentage by weight, relative to the weight of the total composition unless otherwise specified.
As used herein SL formulation, SC formulation and SG formulation are the international denominations adopted by the FAO (Food and Agriculture Organization of the United Nations) to designate soluble liquid, suspension concentrate and soluble granules, respectively.
Compositions comprising a single herbicidally active component suffer from numerous drawbacks such as development of resistant weeds, requirement of high amount and concentration of the active ingredient, environmental damage, seepage of the active component into ground water, phyto-toxicity and harmful effects on the health of animals and humans.
Accordingly, the inventors of the present invention have developed a synergistic herbicidal composition comprising GlyphosateGlyphosate; and ParaquatParaquat dichloride, wherein the mass ratio between GlyphosateGlyphosate, and ParaquatParaquat dichloride ranges from 1:5 to 8:1, and preferably is 2.73:1.( Possible range is given whereas in examples we have only given preferred rangeRange not supported by examples) Preferably, the herbicidal composition contains about 5 to 50% of GlyphosateGlyphosate, and 2 to 25% of ParaquatParaquat dichloride. (Possible range is given whereas in examples we have only given preferred rangeRange not supported by examples)
The synergistic herbicidal composition, further comprises additives selected from the group consisting of anti-freezing agent, dispersing cum wetting agent, defoamer, biocide, thickener, water and combinations thereof, and the composition is in the form of a suspension concentrate (SC). The term “suspension concentrate” used herein refers to a suspension of the active herbicide and additives in a small quantity of liquid, usually water. A composition in the form of a suspension concentrate is user friendly and affords a reduced risk of occupational exposure.
An anti-freezing agent is generally added to herbicidal compositions, to prevent the aqueous compositions from freezing. Suitable anti-freezing agents useful herein include, but not limited to, propylene glycol, Diethylene glycol (DEG), Mono ethylene glycol (MEG) and combinations thereof. Preferably, the anti-freezing agent is present in an amount in the range from 1.00-8.00%.
A dispersing cum wetting agent is another important component of a suspension concentrates as it facilitates the formation of a suspension of a water insoluble substrate in water. Non-limiting examples of dispersing cum wetting agents that can be used in the present invention include non-ionic surfactants and amine salt of phosphate tristyryl phenol ethylated, acrylic copolymer, ethoxylated polyarylphenol phosphate ester, each of which can be used individually or in combination, in an amount in the range from 2.00-10.00%.
A defoamer, also called as anti-foam, is generally added to a 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 0.01-0.50%.
The synergistic herbicidal composition may contain a biocide selected from the group consisting of Proxel GXL, formaldehyde and combinations thereof, and 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.
It is necessary to add a thickener to a herbicidal composition to reduce the tendency of the herbicide composition to disperse when sprayed, and decrease the likelihood of it being rinsed off of the crops. Preferably, the synergistic herbicidal composition comprises xanthan gum as thickener in an amount in the range from 0.10-0.50%.
It has been surprisingly found that the synergistic herbicidal composition of present invention provides a wide spectrum control of weeds, delaying the emergence of the resistant strains of weeds, and achieving effective and economical control of undesired weeds.
The embodiments of the present invention are more particularly described in the following examples that are intended 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 reagents used in the examples were obtained or are available from the chemical suppliers.

EXAMPLES
Example 1
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 composition illustrated in Table 1 is formulated as a suspension concentrate (SC) formulation.
Table 1: Synergistic herbicidal composition
No. Component Function (%)
1 GlyphosateGlyphosate A.I* 41.00
2 ParaquatParaquat Dichloride A.I* 15.00
3 Di-ethylene glycol Anti-freeze Agent 5.00
4 Ethoxylated Polyarylphenol Phosphate Ester Dispersing cum Wetting Agent 5.00
5 Dimethyl Polysiloxane emulsion Deformer 0.20
6 Proxel GXL Biocide 0.20
7 Xanthan Gum Thickener 0.12
8 D.M*** Water Solvent Q.S**
*active ingredient
**quantity sufficient
***demineralized water
The aforementioned synergistic herbicidal composition can be formulated as suspension concentrate (SC) by the process described below.

Process for preparing synergistic herbicide composition in the form of Suspension Concentrate (SC)
The synergistic herbicidal compositions of Examples 1 is prepared by the process depicted in Figure 1. All the raw materials were verified for conformance to the laid down individual specifications. The raw materials required for preparing example 1 is illustrated in table 2. Entries for ParaquatParaquat dichloride and GlyphosateGlyphosate 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. the ones 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.
The required quantities of raw materials as illustrated in Table 2 below, were weighed, and transferred through the auto-batching system. The dispersing cum wetting agent is first diluted in demineralized (D.M.) water and solubilized by high shear mixing, and then added along with required quantities of anti-freezing agent, ParaquatParaquat dichloride technical, deformer and GlyphosateGlyphosate technical, into a premixing vessel, to make a homogeneous mass. Thereafter, the homogenous mass was ground to a mean particle size of 3-5 microns in a bead mil and mixed with 2% aqueous solution of xanthan gum under low stirring. Further, the quality of in-process sample was checked for conformance to the laid out specifications. Finally, the quality approved in-process sample was 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)
GlyphosateGlyphosate (based on 95% w/w minimum purity) *TGAI 43.20
ParaquatParaquat Dichloride (based on 42% w/w minimum purity) *TGAI 35.80
Di-ethylene glycol Anti-freeze Agent 5.00
Ethoxylated Polyarylphenol Phosphate Ester Dispersing cum Wetting Agent 5.00
Dimethyl Polysiloxane emulsion Deformer 0.20
Proxel GXL Biocide 0.20
Xanthan Gum Thickener 0.12
Demineralized Water Solvent 10.48
*Technical Grade Active Ingredient
Evaluation of sStability of synergistic herbicidal combination of GlyphosateGlyphosate and ParaquatParaquat dichloride
For evaluation of stability, samples of synergistic herbicidal combination were stored at -10 0C; 54 0C and room temperature for eight weeks. At the end of storage period, the samples were used to prepare 5% (w/v) solution (5 mL in 100 mL tap water) in 250 mL beaker with the help of mechanical stirrer at 3-4 rounds per second. The solution so obtained was passed through 45 µm mesh sieve. At the end of experiment negligible particles were detected on 45 µm mesh sieve for all the three samples. Table 3 below summarizes the effect of different temperatures on the storage stability of the synergistic herbicidal composition after a storage period of eight weeks.
Table 3: Evaluation of sStability of synergistic herbicidal combination of GlyphosateGlyphosate and ParaquatParaquat dichloride
No. Storage condition Characteristic Requirement Result
Initial Final
1 Eight Weeks @
-10 0C Wet Sieve Test (45 µm mesh); % by mass Min. 98% 99.86% 99.36%
2 Eight Weeks @
54 0C 99.44%
3 Eight Weeks @ Room temperature 99.61%
Appearance of the product was also found unchanged, i.e. the white viscous liquid remained unchanged after a storage period of eight weeks in all the three storage conditions. Results presented in table 3, shows that the synergistic herbicidal composition of glyphosateGlyphosate and paraquatParaquat dichloride has improved storage stability.
Evaluation of bio-efficacy of synergistic herbicidal combination against overall weed population in tea crop
Field tests of the composition according to the present invention were conducted at various trial sites. The performance of the synergistic herbicidal composition according to the present invention was compared against the known compositions of GlyphosateGlyphosate 71% SG (Ammonium Salt); GlyphosateGlyphosate 41% SL Isopropyl amine (IPA) Salt and ParaquatParaquat Dichloride 24% SL which were evaluated against overall weed spectrum in tea crop 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. Based on various doses, weighed quantity of test products were dissolved in 5 liter of water/treatment and sprayed uniformly. Experimental design was in randomized blocks with seven replication and each plot was measured an area of 100 sq. m (10 x 10 m). Observations on weed population, dry weight and weed control efficiency (WCE % Please define) was assessed at 5, 15 and 45 days after application.
Weed Control Efficiency (%) = [(Weed Dry Weight in Control Plot – Weed Dry Weight in Treated PlotWeight)/ 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 bBio-efficacy of novel synergistic herbicidal composition on overall weed spectrum in Tea crop
Particulars Treatment Dose A.I/Acre Dose /Acre Time of Application
T1 GlyphosateGlyphosate 41% and ParaquatParaquat dichloride 15% 246 + 90 600 mL 2-4 Leaf stage (Please define)
T2 GlyphosateGlyphosate 41% and ParaquatParaquat dichloride 15% 328 + 120 800 mL
T3 GlyphosateGlyphosate 41% and ParaquatParaquat dichloride 15% 410 + 150 1000 mL
T4 GlyphosateGlyphosate 71% SG (Ammonium Salt) 568 800 g
T5 GlyphosateGlyphosate 71% SG (Ammonium Salt) 852 1200 g
T6 GlyphosateGlyphosate 41% SL IPA Salt 328 800 mL
T7 GlyphosateGlyphosate 41% SL IPA Salt 492 1200 mL
T8 ParaquatParaquat Dichloride 24% SL 706 1200 mL
T9 ParaquatParaquat Dichloride 24% SL 940 1600 mL
T10 Control (Water Spray) -- --
The bio-efficacy of different spray schedule on tea crop and the treatment wise yield data of tea crop are summarized in Table 5-8 below.
Table 5: Effect of herbicidal compositions on total weed count (no/m2) in Tea crop
No. Treatments Dose per acre Weed Population (no./m2)
5 DAA* 15 DAA* 45 DAA*
1 T1 600 mL 12.67 (3.62) 18.33 (4.34) 26.67 (5.21)
2 T2 800 mL 3.00 (1.87) 8.67 (3.02) 11.00 (3.39)
3 T3 1000 mL 2.33 (1.68) 8.67 (3.02) 10.67 (3.34)
4 T4 800 g 22.33 (4.78) 36.67 (6.09) 40.52 (6.40)
5 T5 1200 g 18.67 (4.37) 29.00 (5.43) 35.67 (6.01)
6 T6 800 mL 27.00 (5.24) 41.67 (6.49) 48.67 (7.01)
7 T7 1200 mL 22.33 (4.78) 33.00 (5.78) 38.67 (6.25)
8 T8 1200 mL 18.00 (4.30) 24.33 (4.98) 41.00 (6.44)
9 T9 1600 mL 16.67 (4.14) 22.33 (4.77) 35.33 (5.98)
10 T10 -- 128.00
(11.33) 146.33 (12.11) 158.33
(12.60)
CD 5% - 1.60 1.67 1.70
* DAA: Days after application; CD 5%: Critical Difference; g = Gram; m2 = Square meter; mL = Millilitre, * Value in Parentheses is v(x+0.5) transformed value.
Table 6: Effect of herbicidal compositions on total weed dry weight (g/m2) in Tea
No. Treatments Dose per acre Total Weed Dry Weight (g/m2)
5 DAA* 15 DAA* 45 DAA*
1 T1 600 mL 8.12 (2.93) 11.68 (3.49) 21.46 (4.68)
2 T2 800 mL 0.10 (0.77) 3.56 (2.01) 7.36 (2.80)
3 T3 1000 mL 0.07 (0.75) 3.46 (1.98) 7.34 (2.80)
4 T4 800 g 13.45 (3.73) 22.38 (4.78) 38.09 (6.21)
5 T5 1200 g 11.87 (3.51) 19.45 (4.46) 34.76 (5.93)
6 T6 800 mL 16.57 (4.13) 25.77 (5.12) 45.52 (6.78)
7 T7 1200 mL 13.50 (3.74) 20.68 (4.60) 37.67 (6.17)
8 T8 1200 mL 10.03 (3.24) 16.28 (4.09) 34.73 (5.93)
9 T9 1600 mL 8.13 (2.93) 12.68 (3.63) 29.91 (5.51)
10 T10 -- 68.83 (8.32) 98.27 (9.93) 140.00 (11.85)
CD 5% - 1.36 1.39 1.48
* DAA: Days after application; CD 5%: Critical Difference; g = Gram; m2 = Square meter; mL = Millilitre
* Value in Parentheses is v(x+0.5) transformed value.

Table 7: Weed Control Efficacy (WCE %) Effect of herbicidal compositions on Weed Control Efficacy (WCE Please define) (%) in Tea crop
No. Treatments Dose per acre Weed Control Efficacy (%)
5 DAA* 15 DAA* 45 DAA*
1 T1 600 mL 88.20 88.11 84.67
2 T2 800 mL 99.85 96.37 94.74
3 T3 1000 mL 99.89 96.47 94.75
4 T4 800 g 80.45 77.22 72.79
5 T5 1200 g 82.75 80.20 75.17
6 T6 800 mL 75.9 73.77 67.48
7 T7 1200 mL 80.38 78.95 73.09
8 T8 1200 mL 85.42 83.43 75.19
9 T9 1600 mL 88.18 87.09 78.63
10 T10 -- - - -
* DAA: Days after application; g = Gram; mL = Millilitre
Data presented in tables 5, 6 and 7 shows that weed population was significantly affected by all the treatments compared to control when observed at 5, 15 and 45 days after application (DAA). At 45 DAA, GlyphosateGlyphosate 41% and ParaquatParaquat dichloride 15% @ 800 & 1000 mL recorded lowest weed population closely followed by T1 and T9. Similar results were observed in case of weed dry weight and weed control efficacy (WCE), where highest WCE of 94.74% & 94.75 was observed in case of plots treated with GlyphosateGlyphosate 41% and ParaquatParaquat dichloride 15% @ 800 & 1000 mL formulation at 45 DAA.
Table 8: Treatment Wise Yield of Green Tea Leaves
Treatment Green Leaf Yield (kg/plot)
T1 67.30
T2 78.15
T3 78.18
T4 56.80
T5 59.25
T6 49.86
T7 58.28
T8 61.49
T9 63.72
T10 42.70
CD 5% 1.29
CD 5%: Critical Difference
Highest green tea leaf yield of 78.15 and 78.18 kg/100 sq m plot was recorded in treatment of GlyphosateGlyphosate 41% and ParaquatParaquat dichloride 15% @ dose of 800 and 1000 mL/acre respectively. It was thus concluded that the GlyphosateGlyphosate 41% and ParaquatParaquat dichloride 15% @ 800 mL/acre was the best composition to control weeds flora in tea and to obtain better yield attributes.
Phytotoxic effect of herbicidal compositions onin tea crop
Visual observations on phytotoxicity were recorded for leaf injury on tip/surface, Epinasty/Hyponasty, and wilting, etc. on 0-10 scale (Table 9) at 1, 3, 7, 14 and 21 days after application (DAA) and the average values are presented in table 10.

Table 9. 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 10: Phytotoxicity Effect of new the herbicidal compositione on the Phytotoxicity in Tea crop
No. Treatments Dose (mL/acre) Phytotoxicity (Days after Application(DAA))
1 3 7 14 21
1 GlyphosateGlyphosate 41% and ParaquatParaquat dichloride 15% 600 0 0 0 0 0
800 0 0 0 0 0
3 1000 0 0 0 0 0
4 1600 0 0 0 0 0
5 2000 0 0 0 0 0
6 3000 0 0 0 0 0
7 Control - 0 0 0 0 0
0= No Phytoxicity
It is evident from the phytotoxicity data illustrated in table 10 that a herbicidal composition comprising GlyphosateGlyphosate 41% and ParaquatParaquat dichloride 15% upto 3000 mL/acre is non-phytotoxic.
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 aspect 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) Glyphosate; (b) Paraquat dichloride, and additives.
2. The synergistic herbicidal composition, as claimed in claim 1, wherein the mass ratio between Glyphosate, and Paraquat dichloride or its salts ranges from 1:5 to 8:1, and preferably is 2.73:1.
3. The synergistic herbicidal composition, as claimed in claims 1 and 2, wherein Glyphosate is present in an amount of 5 to 50% and Paraquat dichloride is present in an amount in the range from 2 to 25%.
4. The synergistic herbicidal composition, as claimed in claims 1 to 3, wherein the composition may be in the form of a suspension concentrate (SC), soluble granules (SG) or soluble liquid (SL).
5. The synergistic herbicidal composition, as claimed in claims 1 to 4, wherein the additives are selected from the group consisting of anti-freezing agent, dispersing cum wetting agent, defoamer, biocide, thickener, water and combinations thereof, and the composition is in the form of a suspension concentrate (SC).
6. The synergistic herbicidal composition, as claimed in claim 5, wherein the anti-freezing agent is selected from the group consisting of propylene glycol, di-ethylene glycol (DEG), ,mono-ethylene glycol (MEG) and combinations thereof, and present in an amount in the range from 1.00-8.00%.
7. The synergistic herbicidal composition, as claimed in claim 5, wherein the dispersing cum wetting agent is selected from the group consisting of mixture of non-ionic surfactants and amine salt of phosphate tristyryl phenol ethylated, acrylic copolymer, ethoxylated polyarylphenol phosphate ester and combinations thereof, and present in an amount in the range from 2.00-10.00%.
8. 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 0.01-0.50%.
9. The synergistic herbicidal composition, as claimed in claim 5, wherein the biocide is selected from Proxel GXL or formaldehyde and present in an amount in the range from 0.01-0.50%.
10. The synergistic herbicidal composition, as claimed in claim 5, wherein the thickener is Xanthan gum and present in an amount in the range from 0.10-0.50%.
11. The synergistic herbicidal composition as claimed in any of the claims 1 to 10, wherein said composition is non-phytotoxic.