Herbicidal microencapsulated clomazone compositions with reduced vapor transfer

There is provided an aqueous dispersion of microcapsules containing the herbicide clomazone dissolved in an inert high boiling organic solvent. Vapor transfer of the herbicide outside the targeted area is controlled without substantial sacrifice of the efficacy of the herbicide.

BACKGROUND OF THE INVENTION 
The present invention relates to new and useful herbicidal compositions and 
particularly relates to herbicidal compositions requiring special 
precautions when being applied to reduce or prevent vapor transfer thereof 
to plants which are not the target of application of the compositions. 
Agricultural chemicals, particularly herbicides, are sold and delivered to 
applicators in a wide variety of formulations, including solid 
formulations, such as powders, dusts and granules and time-release 
microcapsules, liquid formulations, such as solutions, oil concentrates, 
and emulsions, and suspensions of solids in liquid carriers, such as 
time-release microcapsules dispersed in an aqueous carrier. The choice of 
which type of selected formulation to be used is generally governed by 
many considerations, such as the physical characteristics of the active 
ingredients, the crop or weed species to which the formulation is to be 
applied, and whether the application is better made postemergence or 
preemergence. 
Delayed-release formulations are chosen normally to provide pesticidal 
efficacy over an extended period of time. Microencapsulation of the 
pesticide is one delivery form often selected for providing the desired 
delayed-release. Applying microencapsulated pesticide has, in some cases, 
the disadvantage of substantially sacrificing the activity of the 
pesticide in the proper point of time. 
An excellent selective soil applied herbicide commercially available for 
controlling many broadleaf and grass weeds, in soybean, cotton, sugarcane, 
rice, tobacco, oilseed rape, vegetables and others has the common name 
clomazone which chemically is 
2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone. For brevity 
reasons the herbicidally active ingredient to which the present invention 
is concerned will be referred to herein by its common name of clomazone. 
Clomazone is an effective herbicide as evidenced by its ability to 
control, for full growing seasons and at low application rates in crops, a 
broad spectrum of grasses and broadleaf weeds that compete with crops. 
Unfortunately, clomazone is phytotoxic to some nontargeted crops and 
naturally occurring plant species when applied to control undesired 
vegetation. Contact of clomazone with such crops is the result of vapor 
transfer of the clomazone to sensitive species growing in adjacent areas. 
Although clomazone can be, and is, sold with suitable label instructions to 
prevent exposure to sensitive crops, it will be evident that measures that 
will further decrease the exposure of the nontargeted crops to clomazone 
without substantial diminution of herbicidal efficacy against weeds, will 
greatly expand the usefulness of clomazone and thus result in lower 
overall costs. 
Solvent-based emulsifiable concentrate (EC) formulations of clomazone may 
be prepared by dissolving the same in an inert organic liquid solvent, 
together with an appropriate emulsifier system which, when mixed with 
water, spontaneously forms an oil in water emulsion of the 
clomazone/solvent solution. Suitable solvents and emulsifiers are well 
known to those skilled in the art. 
In conventional practice, until now, the propensity of clomazone EC to 
adversely affect vegetation outside the treated area has been best 
controlled by preplant incorporation of the herbicide into the soil. As a 
matter of fact, in many geographical areas, application of the herbicide 
by means of preplant incorporation is required to control movement of the 
herbicide vapors to plants outside the targeted area, where plants are 
sensitive to clomazone. Other restrictions on application include the use 
of special nozzles and the addition of drift reducing chemical agents 
which add to the cost of the clomazone treatment. 
Preplant incorporation of a herbicide is an expensive operation requiring 
additional labor, fuel and land tillage to accomplish. Vapor transfer of 
clomazone to nontargeted sites during spraying is controlled in a limited 
way by careful attention to many operational parameters, including wind 
speed, spray pressure, droplet particle size, nozzle types and boom 
height. Taking the necessary precautions to minimize the off target 
movement of clomazone vapors is obviously an undesirable expense. 
The present invention provides the art with a system for formulating and 
spraying of clomazone to control undesirable vegetation encountered in the 
cultivation of various plant species, particularly agronomic crops, while 
minimizing off-target vapor transfer of the herbicide. Thus, a cost 
effective means is provided by the practice of the present invention, 
wherein off-site vegetation injury is reduced while maintaining acceptable 
herbicidal effectiveness with surface applied clomazone-containing 
herbicidal compositions. 
SUMMARY OF THE INVENTION 
In accordance with the present invention there is provided an aqueous 
dispersion of microcapsules containing a herbicidally effective amount of 
clomazone dissolved in a suitable water-immiscible high boiling inert 
organic solvent. The boiling point of the solvent is, preferably, above 
170.degree. C. The encapsulant is a porous condensate polymer of polyurea, 
polyamide or amide-urea copolymer. To provide acceptable volatility 
control without unacceptable sacrifice of herbicidal efficacy, the 
percentage of polymer comprising the microcapsules ranges from about 3 to 
about 15 by weight, preferably about 5 to about 12 by weight. Also the 
percentage of solvent of the encapsulated material ranges from about 10 to 
about 50 by weight, preferably about 20 to 35 by weight. The microcapsules 
of the present invention provide volatility reduction of about 20-90 
percent as compared with clomazone prepared and applied from an 
emulsifiable concentrate which is commercially available at the present 
time. When the composition of the present invention is sprayed or 
otherwise applied to the surface of soil at the proper dilution for 
controlling vegetation, it has been found that by encapsulating clomazone 
dissolved in a suitable water-immiscible inert organic solvent as 
described and claimed herein, clomazone may be surface-applied directly by 
spraying and that one may achieve effective weed control in crops without 
significant damage to neighboring unsprayed vegetation due to vapor 
transfer of the herbicide. Thus, the practice of the present invention, 
among other things, enables one to surface apply clomazone to control 
weeds in crops while eliminating or substantially diminishing the risk of 
clomazone injury to plant species located in areas adjacent thereto 
without the need to resort to expensive and time-consuming preplant 
incorporation or special application procedures.

DETAILED DESCRIPTION OF THE INVENTION 
During the first step in preparing the formulation of the present 
invention, an aqueous suspension of microcapsules containing the selected 
clomazone organic solution is provided. The walls of the microcapsules are 
made of a porous polymer, such as polyurea. The microcapsule preparation 
comprises initially providing an aqueous solution containing an 
emulsifier, selected preferably from the group of the salts of 
ligninsulfonic acid, for example, the sodium, potassium, magnesium, and 
calcium, salts. Particularly effective is the sodium salt of 
ligninsulfonic acid. A solution of clomazone and polyfunctional 
polyisocyanate is added to the composition of water and lignosulfonate 
surfactant. The solvent in which clomazone is dissolved is a 
water-immiscible high boiling inert organic solvent having a boiling 
point, preferably, above 170.degree. C. The resulting mixture is stirred 
sufficiently under suitable conditions to form a homogenous dispersion of 
small droplets of the pesticide within the aqueous phase. 
Thereafter, a polyfunctional amine is added with the stirring being 
continued until the polyfunctional amine has essentially fully reacted 
with the polyfunctional isocyanate. The polyfunctional isocyanate and the 
polyfunctional amine react in the presence of the surfactant under proper 
agitation and reaction conditions to form microcapsules having polyurea 
walls encapsulating the herbicide. The rate of the polymerization will 
depend on the reaction conditions employed. The rate of polymerization 
will generally be directly related to the temperature at which the 
reaction takes place. 
The encapsulation process of the present invention is capable of 
satisfactory performance and production of encapsulated material without 
adjustment to a specific pH value. That is, as a rule no adjustment of the 
pH of the system need be made during the encapsulation process. If it is 
desired to adjust the pH of the finished microcapsule formulation as, for 
example, when the aqueous base formulation of the microcapsules is 
combined with other herbicides, fertilizers, etc., conventional and 
suitable reagents for pH adjustment may be used. Such reagents include 
hydrochloric acid, acetic acid, phosphoric acid, sodium hydroxide, 
potassium hydroxide, etc. 
The agitation employed to establish the dispersion of water immiscible 
phase droplets in the aqueous phase during the production of the 
formulation of the present invention may be supplied by any means capable 
of providing suitable high shear. That is to say that any variable shear 
mixing apparatus, e.g., a Waring Blender, a Brinkman Polytron homogenizer, 
Ross Model 100L homogenizer and the like can be usefully employed to 
provide the desired shear. 
The particular size of the microcapsules for formulating the composition of 
the present invention will range from about one micron up to about one 
hundred microns in average diameter. From about one to about twenty 
microns is a preferred average range. The size distribution of the 
microcapsules is not of critical importance. 
Among suitable water-immiscible highly boiling inert organic solvents in 
which clomazone is dissolved are mixtures of mono- and polyalkylated 
aromatics commercially available from Shell Oil Co. under the trademark 
SHELLSOL, various petroleum fluids available from Exxon such as Aromatic 
200, AE700, and Exxate 700, various fatty acid methyl esters available 
from Henkel Corporation, such as Emery 2209, Emery 2270, and Emery 2301. 
The selected organic solvent has a boiling point above 170.degree. C. 
The homogenous dispersions of polymer microencapsulated pesticides in water 
with an effective emulsifier, such as lignosulfonate prepared in the first 
step, may be blended with a suspension system composition. The suspension 
system composition may comprise a combination of agents, such as 
surfactants, dispersants, antifreeze agents, clays, water, salts, 
polymers, and other suspension stabilizing and density balancing agents, 
appropriately selected to keep the microcapsules in stable homogeneous 
suspension in the water-based carrier over an extended period of time as 
long as for example two years or more. The agents comprising the 
suspension system will generally comprise 1 percent by weight to 15 
percent by weight of the formulation and preferably 2 percent by weight to 
10 percent by weight. 
A wide range of such agents may be used, and the optimum combination for 
each particular suspension system of active ingredient will vary. Suitable 
clays include bentonite clay and attapulgite clay and mixtures thereof, 
preferably in the range from about 0.01% to about 1.0% solid by weight, 
relative to the total formulation weight although greater or lesser 
amounts may be employed. The presence of at least one clay conventionally 
used in suspension systems improves the stability of the suspended 
microcapsules and particularly aids in the redistribution of the 
microcapsules upon shaking in the event some settling of microcapsules is 
experienced and redistribution thereof is required. 
Another preferred suspension system may also include a small amount of a 
xanthan gum thickening agent to aid in stabilizing the suspension of the 
microcapsules. The gum is preferably present in an amount in the range 
from about 0.01 percent by weight to about 0.1 percent by weight although 
greater or lesser amounts may be employed. 
In the preferred final product about 100 to 750 grams of microcapsules 
(polymer plus encapsulated material) per liter of the composition and more 
preferably about 400 to about 600 grams microcapsules per liter are 
present. The encapsulating polymer component to the encapsulated pesticide 
normally will be in the range of about 0.02 percent by weight to about 5.0 
percent by weight and preferably in the range of about 0.04 percent by 
weight to about 4.0 percent by weight. 
Within the scope of this invention, polyisocyanates will be generally 
understood as meaning those compounds that contain two and more isocyanate 
groups in the molecule. Preferred isocyanates are di- and triisocyanates 
whose isocyanate groups may be linked to an aliphatic or aromatic moiety. 
Examples of suitable aliphatic diisocyanates and aliphatic triisocyanates 
are tetramethylene diisocyanate, pentamethylene diisocyanate, 
hexamethylene diisocyanate and 4-(isocyanatomethyl)-1,8-octyl 
diisocyanate. Suitable aromatic isocyanates are toluene diisocyanate (TDI: 
DESMODUR Registered TM VL, Bayer), polymethylene polyphenylisocyanate 
(MONDUR Registered TM MR, Miles Chemical Company); PAPI Registered TM, 
PAPI Registered TM 135 (Upjohn Company), 2,4,4'-diphenyl ether 
triisocyanate, 3,3'-dimethyl-4,4'-diphenyl diisocyanate, 
3,3'-dimethoxy-4,4'diphenyl diisocyanate, 1,5-naphthalene diisocyanate and 
4,4',4"-triphenylmethane triisocyanate. A further suitable diisocyanate is 
isophorone diisocyanate. Also suitable are adducts of diisocyanates with 
polyhydric alcohols, such as ethylene glycol, glycerol and 
trimethylolpropane, obtained by addition, per mole of polyhydric alcohol, 
of a number of moles of diisocyanate corresponding to the number of 
hydroxyl groups of the respective alcohol. In this way several molecules 
of diisocyanate are linked urethane groups to the polyhydric alcohol to 
form high molecular polyisocyanates. Another suitable product of this kind 
(DESMODUR Registered TM L) can be prepared by reacting three moles of 
toluene diisocyanate with one mole of 2-ethylglycerol 
(1,1-bismethylolpropane). Further suitable products are obtained by 
addition of hexamethylene diisocyanate or isophorone diisocyanate with 
ethylene glycol or glycerol. Preferred polyisocyanates are 
diphenylmethane-4,4'-diisocyanate and polymethylene polyphenylisocyanate. 
The di- and triisocyanates specified above can be employed individually or 
as mixtures of two or more such isocyanates. 
Suitable polyamines within the scope of this invention will be understood 
as meaning in general those compounds that contain two or more primary 
amino groups in the molecule, which amino groups maybe linked to aliphatic 
and aromatic moieties. 
Examples of suitable aliphatic polyamines are alpha, omega-diamines of the 
formula H.sub.2 N(CH.sub.2).sub.n NH.sub.2 wherein n is an integer from 2 
to 6. Exemplary of such diamines are ethylenediamine, 
propylene-1,3-diamine, tetramethylenediamine, pentamethylenediamine and 
hexamethylenediamine. A preferred diamine is hexamethylenediamine. 
Further suitable aliphatic polyamines are polyethyleneamines of the formula 
H.sub.2 N(CH.sub.2 CH.sub.2 NH).sub.n H wherein n is an integer from 2 to 
5. Representative examples of such polyethyleneamines are: 
diethylenetriamine, triethylenetriamine, tetraethylenepentamine, 
pentaethylenehexamine. 
Examples of suitable aromatic polyamines are 1,3-phenylenediamine, 
2,4-toluylenediamine, 4,4'-diaminodiphenylmethane, 1,5-diaminoaphthalene, 
1,3,5-triaminobenzene, 2,4,6-triaminotoluene, 1,3,6-triaminonaphthalene, 
2,4,4'-triaminodiphenyl ether, 3,4,5-triamino-1,2,4-triazole, 
bis(hexamethylentriamine) and 1,4,5,8-tetraaminoanthraquinone. Those 
polyamines which are insoluble or insufficiently soluble in water may be 
used as hydrochloride salts. 
Yet further suitable polyamines are those that contain sulfo or carboxyl 
groups in addition to the amino groups. Examples of such polyamines are 
1,4-phenylene diaminesulfonic acid, 4,4'-diaminodiphenyl-2-sulfonic acid, 
or diaminoammocarboxylic acids such as ornithene and lysine. 
Suitable liquid fertilizers can be mixed with the formulations herein 
without the formation of unacceptable amounts of agglomerates in the spray 
tank, thus avoiding poor spraying performance. The liquid fertilizers used 
in mixtures of the present invention can be liquid nitrogen fertilizers, 
optionally containing phosphate and/or potash components. Liquid 
fertilizers are usually designated by the percentage weight of nitrogen, 
phosphorous and potassium (N-P-K) ratios, e.g., 4-10-10, 6-18-18, or 
10-30-10. 
The present invention is better illustrated and is explained in more detail 
in the following examples wherein parts and percentages are given on a 
weight basis unless otherwise stated. It should be understood that the 
examples are merely illustrative of the invention and not limitative. 
EXAMPLE I 
This example illustrates the preparation of an aqueous suspension of 
microencapsulated clomazone solution. In the microencapsulation operation, 
microcapsules containing a solution of clomazone and AE700 solvent were 
prepared from the following components. 
TABLE 1 
______________________________________ 
Component 
Parts 
______________________________________ 
Clomazone 
97.5 
(Technical).sup.1 
AE700.sup.2 
97.5 
PAPI 2027.sup.3 
20.4 
HMD.sup.4 
20.4 
REAX 88B.sup.5 
145.7 
381.5 
______________________________________ 
1. 90% active ingredient. 
2. Aromatic ester solvent obtained from Exxon Chemical which chemically i 
identified as 1,2benzenedicarboxylic di (C.sub.6 -C.sub.8), branched alky 
ester. 
3. Polymethylene polyphenylisocyanate produced by Dow Chemical having an 
average functionality of 2.7 and a typical isocyanate equivalent weight o 
134. 
4. Hexamethylenediamine (43% aq. sol.). 
5. Na salt of ligninsulfonic acid (3.0% aq. sol.). 
Appropriate amounts of PAPI, clomazone, and AE700 solvent were stirred 
together to form a uniform liquid mixture. In a Waring blender cup 
containing the REAX 88B solution preheated to about 50.degree. C., the 
shear was gradually increased with concurrent addition of the 
PAPI-clomazone-AE700 solvent mixture to form a uniform emulsion. The 
higher level of shear was continued for about 30 seconds. Thereafter, the 
shear was reduced to an intermediate level that was about one-half of the 
initial level, and the HMD component was added while maintaining this 
intermediate shear, whereupon microcapsules of diameters in the range of 2 
to 20 microns on an average in an aqueous suspension were formed. The 
walls of the microcapsules were made of polymeric urea and encompassed the 
clomazone-containing solution. Sixty seconds after the HMD addition was 
completed, the shear was reduced to a low level which provided shear 
sufficient to maintain continuous agitation. This microencapsulated 
feedstock was allowed to cool at low shear under ambient conditions for 
about 30 minutes before subsequent components were added. 
In the blending and suspension operations, 37 parts of sodium nitrate and 
2.2 parts of 48.5 percent aluminum sulfate as densification salts were 
added to the microencapsulated feedstock at low shear to form a 
microcapsule-containing aqueous suspension. The nitrate salt significantly 
enhanced the density of the aqueous phase of the product. Finally, 13 
parts of an aqueous solution containing 1.5 percent xanthan gum thickener 
(Keltrol RD) and a biocidal amount of Legend biocide were added to the 
densified aqueous suspension. After maintaining low shear agitation for an 
additional 10 minutes, the resulting product was allowed to cool to room 
temperature. The formulation was characterized as having 12 percent 
polymer, 22.5 percent solvent and 22.5 percent clomazone. 
EXAMPLE II 
Additional formulations were prepared in accordance with Example I, except 
that various combinations of percent polymer and percent encapsulated 
herbicide solution were used as set out in Table 2 below. The formulation 
of Example 1 is identified as Sample ID 9 in the table. 
TABLE 2 
______________________________________ 
% AE700 
Sample ID 
% Polymer Solvent % Clomazone 
______________________________________ 
1 3 25.0 31.1 
2 3 37.5 25.8 
3 3 50.0 20.6 
4 7 12.5 36.1 
5 7 25.0 31.1 
6 7 37.5 25.8 
7 7 50.0 20.6 
8 11 12.5 36.1 
9 11 25.0 31.1 
10 11 37.5 25.8 
11 15 12.5 35.7 
12 15 25.0 30.6 
13 15 37.5 25.5 
14 15 50.0 20.5 
______________________________________ 
It was noted that the resulting samples were homogenous suspensions. 
EXAMPLE III 
This example illustrates the method used to quantify off-site injury of 
neighboring vegetation due to vapor drift of clomazone and bioefficacy or 
weed control of example formulations. 
Square plots with 20-foot (7.1 meter) sides were planted at least two weeks 
prior to chemical application with a species known to be sensitive to 
clomazone bleaching, namely wheat. A 22-inch (0.56 meter) diameter circle 
in the center of each plot, designated the target application area, was 
hand-weeded and watered just prior chemical application to provide a wet, 
bare soil surface. A circular 32-gallon (121 liter) plastic barrel with 
its bottom and top removed was then placed vertically on the target 
application area. 
A spray solution was prepared by diluting the test formulation with water 
such that 220 gallons per acre (2056 liters per hectare) were applied 
through a single nozzle at 20 psi (138 kilo Pascals) at a rate of 2.24 
kilograms per hectare. The spray solution was applied to the soil surface 
inside the barrel. Before removing the barrel, a waiting period of one 
minute transpired to assure that all spray droplets have settled to the 
ground. 
At various times from three to fourteen days after treatment, measurements 
were taken of the distance from the outer edge of the target application 
circle to the location of a herbicidally vapor transfer affected plant 
observed to be farthest from the edge of the clomazone treated circle. 
To compare the percent volatility suppression improvement obtained by the 
practice of the present invention, various formulations of Example II were 
evaluated by the just-described test procedure against commercially 
obtained COMMAND.RTM. 4EC herbicide composed of 47 percent clomazone and 
53 percent inerts formulated as an emulsifiable concentrate in 
side-by-side tests. The improvement in percent vapor transfer reduction 
(VTR) is seen in Table 3 below. 
To compare bioefficacy or weed control of examples, an area of 4.5 square 
meters was treated with a rate of 0.84 kilograms per hectare of clomazone 
contained in each example. Three replicates of each example were observed 
for weed control or bioefficacy by observing the percentage of undesirable 
species which emerged in these plots after application of the example 
formulas as compared to an untreated control. 
Percent (VTR) is determined by the following equation. 
##EQU1## 
TABLE 3 
______________________________________ 
% 
Sample Vapor Transfer 
% 
ID Distance Reduction Bioefficacy 
______________________________________ 
Command 100 0 74.5 
4EC 
1 88 12 84.0 
2 64 36 78.5 
3 36 64 77.5 
4 95 5 84.0 
5 60 40 76.0 
6 25 75 65.0 
7 10 90 52.0 
8 72 28 78.0 
9 18 82 65.0 
10 5 95 51.5 
11 43 57 70.0 
12 6 94 39.5 
13 6 94 28.5 
14 0 100 35 
______________________________________ 
With reference to the drawing, it is noted that a 40 percent improvement in 
VTR can be obtained when the microcapsules are composed of 6 percent 
polymer and the encapsulated clomazone solution contains about 25 percent 
organic solvent as compared to the use of the commercial EC product with 
good weed control being obtained. A 75 percent VTR with acceptable weed 
control can be obtained when the microcapsules are composed of 12 percent 
polymer and the encapsulated clomazone solution contains 21 percent 
organic solvent. A 90 percent VTR can be obtained when the microcapsules 
were composed of 9 percent polymer and the encapsulated clomazone solution 
contained 43 percent solvent but the weed control level was significantly 
reduced. 
With reference to the drawing, it is seen that as compared to the use of 
the commercial EC product, about 50 percent improvement in VTR is achieved 
while maintaining good weed control when the microcapsules are composed of 
3 percent polymer and 40 percent solvent. About 50 percent VTR with 
acceptable weed control is obtained when the microcapsules are composed of 
7 percent polymer and the encapsulated clomazone solution contains 25 
percent organic solvent (Sample 6). A 95 percent VTR is obtained when the 
microcapsules are composed of 11 percent polymer and the encapsulated 
clomazone solution contains 37.5 percent solvent (Sample 10), but the weed 
control level is reduced. 
In the above examples of the present invention, REAX 88B lignosulfonate 
surfactant was obtained from Westvaco Corporation and had a nominal degree 
of sulfonation of about 3.8. The sulfonic acid groups were located both on 
aromatic ring and aliphatic side chains. 
Legend MK biocide was obtained from Rohm and Haas as a mixture of two 
isothiazolones as the active ingredients, namely 
5-chloro-2-methyl-4-isothiazolin-3-one- and 2-methyl-4-isothiazolin-3-one. 
The xanthan gums were obtained from Merck & Co., Inc., under the names 
KELZAN S and Keltrol RD in the form of a dry powder. 
Similar excellent results as obtained in the above examples can be obtained 
when different polyurea-forming substances, different suspending aids and 
other solvents salts are employed. For example, the urea polymer can be 
formed by the hydrolysis of an isocyanate monomer to form an amine which, 
in turn, reacts with another isocyanate monomer to form polyurea. 
Although the above examples illustrate the use of lignosulfonate as a 
preferred surface active agent in the microencapsulation step, other known 
surface active agents can also be used, for example, the sodium salt of 
alkylnaphthalene sulfonic acid, the potassium salt of alkylnaphthalene 
sulfonic acid, salts of polystrenesulfonic acid, in particular, the alkali 
metal, alkaline earth metal and ammonium salts thereof, and salts of 
condensates of napthalenesulfonic acids, etc., and mixtures thereof. The 
dispersant system for the microencapsulation process may also optionally 
contain one or more non-ionic surfactant, non-ionic protective colloid, or 
a cationic component. 
Ordinarily, the formulations may be applied without further dilution or as 
dilute suspensions in water or other suitable diluent. The compositions 
may be applied to the area wherein control is desired, prior to or after 
emergence in the case of agronomic crops, by spraying onto the surface of 
the soil in the case of liquid compositions. The user may, if desired, 
blend the clomazone formulation into the upper layer of soil by 
cultivation. 
Clomazone may be formulated and/or applied together with other herbicides 
compatible therewith insecticides, fungicides, nematocide, plant growth 
regulators, safeners, fertilizers, and other agricultural chemicals. In 
applying the other active compounds with the formulation of this 
invention, whether formulated alone or with other agricultural chemicals, 
an effective amount of each active ingredient is employed. The amount 
constituting an effective amount is variable, depending on the ratio of 
added ingredients to clomazone and other factors, such as the type of 
soil, the expected pattern of rainfall or irrigation, the plant species to 
be controlled, and the crop, if any, to be grown. Generally, a uniform 
application of from about 0.01 to about 2.0 kilogram per hectare of 
clomazone will be employed, more preferably about 0.3 to about 1.5 
kilogram per hectare. Generally, the rate of application of clomazone in 
the field will be about two to four times that in the greenhouse. 
Acetochlor, alachlor and metolachlor are preferred herbicides for forming 
mixtures with clomazone. 
As can be seen above, by the practice of the present invention one can 
reduce off-site injury to plants while maintaining the herbicidal 
effectiveness of a surface-applied clomazone. 
While the illustrative embodiments of the invention have been described 
with particularity, it will be understood that various other modifications 
will be apparent to and can be readily made by those skilled in the art 
without departing from the spirit and scope of the invention. Accordingly, 
it is not intended that the scope of the claims appended hereto be limited 
to the examples and description set forth hereinabove; but rather it is 
understood that the claims are to be construed as encompassing all the 
features of patentable novelty which reside in the present invention as 
described herein, including all features which would be treated as 
equivalents thereof by those skilled in the art to which the invention 
pertains.