compound a and compound b sometimes form salts or have isomers , and they are included in the present invention so long as they are agriculturally acceptable . the mixing ratio of compound a to compound b cannot generally be defined , as it varies depending upon various conditions such as the type of the formulation , the weather conditions , and the type and the growth stage of the undesired plants , and is , for example , from 1 : 0 . 2 to 1 : 50 , preferably from 1 : 0 . 8 to 1 : 40 , further preferably from 1 : 1 to 1 : 30 by the weight ratio . the herbicidally effective amounts of compounds a and b cannot generally be defined , as they vary depending upon various conditions such as the mixing ratio of compound a to b , the type of the formulation , the weather conditions , and the type and the growth stage of the undesired plants . however , for example , compound a is applied in an amount of from 10 to 100 g / ha , preferably from 10 to 50 g / ha , and compound b is applied in an amount of from 20 to 500 g / ha , preferably from 40 to 400 g / ha , further preferably from 50 to 300 g / ha . the herbicidal composition of the present invention may be applied to undesired plants or may be applied to a place where they grow . further , it may be applied at any time either before or after the emergence of the undesired plants . further , the herbicidal composition of the present invention may take various application forms such as soil application , foliar application , irrigation application , and submerged application , and it can be applied to agricultural fields such as upland fields , orchards and paddy fields , and non - cropland such as ridges of fields , fallow fields , play grounds , golf courses , vacant lands , forests , factory sites , railway sides and roadsides . the herbicidal composition of the present invention can control a wide range of undesired plants such as annual weeds and perennial weeds . the undesired plants to be controlled by the herbicidal composition of the present invention may , for example , be specifically cyperaceae such as green kyllinga ( kyllinga brevifolia rottb . var . leiolepis ), sedge ( cyperus spp .) ( such as purple nutsedge ( cyperus rotundus l . ), smallflower umbrella sedge ( cyperus difformis l . ), yellow nutsedge ( cyperus esculentus l .) or amur cyperus ( cyperus microiria steud . )); gramineae such as barnyardgrass ( echinochloa crus - galli l ., echinochloa oryzicola vasing . ), crabgrass ( digitaria spp .) ( such as summergrass ( digitaria ciliaris ( retz .) koel ), large crabgrass ( digitaria sanguinalis l . ), violet crabgrass ( digitaria violascens link ) or digitaria horizontalis willd . ), green foxtail ( setaria viridis ( l . )), giant foxtail ( setaria faberi herrm . ), goosegrass ( eleusine indica l . ), sorghum ( sorghum spp .) ( such as johnsongrass ( sorghum halepense ( l .) pers .) or shattercane ( sorghum bicolor ( l .) moench . )), oat ( avena spp .) ( such as wild oat ( avena fatua l . )), annual bluegrass ( poa annua l . ), panic grass ( panicum spp .) ( such as guinea grass ( panicum maximum jacq .) or fall panicum ( panicum dichotomiflorum ( l .) michx . )), signal grass ( brachiaria spp .) ( such as plantain signal grass ( brachiaria plantaginea ( link ) hitchc . ), palisade signal grass ( brachiaria decumbens stapf ) or mauritius signal grass ( brachiaria mutica ( forssk .) stapf )), paspalum ( paspalum spp . ), itchgrass ( rottboellia cochinchinensis ( lour .) w . d . clayton ) or bermudagrass ( cynodon dactylon pers . ); scrophulariaceae such as persian speedwell ( veronica persica poir .) or corn speedwell ( veronica arvensis l . ); compositae such as beggar ticks ( bidens spp .) ( such as hairy beggarticks ( bidens pilosa l . ), devils berggarticks ( bidens frondosa l . ), bidens biternata ( lour .) merr . et sherff or beggarticks ( bidens subalternans dc . )), hairy fleabane ( conyza bonariensis ( l .) cronq . ), horseweed ( erigeron canadensis l . ), dandelion ( taraxacum officinale weber ), common cocklebur ( xanthium strumarium l .) or common ragweed ( ambrosia artemisiifolia l . ); leguminosae such as rattlepod or rattlebox ( crotalaria spp .) ( such as sunn - hemp ( crotalaria juncea l . )), poison bean ( sesbania spp .) ( such as rostrate sesbania ( sesbania rostrata bremek . & amp ; oberm .) or sesbania pea ( sesbania cannabina ( retz .) pers . )), white clover ( trifolium repens l .) or common lespedeza ( lespedeza striata ( thunb .) hook . et . arn . ); caryophyllaceae such as sticky chickweed ( cerastium glomeratum thuill .) or common chickweed ( stellaria media l . ); euphorbiaceae such as garden spurge ( euphorbia hirta l . ), threeseeded copperleaf ( acalypha australis l .) or fireplant ( euphorbia heterophylla l . ); plantaginaceae such as asiatic plantain ( plantago asiatica l . ); oxalidaceae such as creeping woodsorrel ( oxalis corniculata l . ); apiaceae such as lawn pennywort ( hydrocotyle sibthorpioides lam . ); violaceae such as violet ( viola mandshurica w . becker ); iridaceae such as blue - eyedgrass ( sisyrinchium rosulatum bicknell ); geraniaceae such as carolina geranium ( geranium carolinianum l . ); labiatae such as purple deadnettle ( lamium purpureum l .) or henbit ( lamium amplexicaule l . ); malvaceae such as velvetleaf ( abutilon theophrasti medic .) or prickly sida ( sida spinosa l . ); convolvulaceae such as ivy - leaved morningglory ( ipomoea hederacea ( l .) jacq . ), common morningglory ( ipomoea purpurea roth ), cypressvine morningglory ( ipomoea guamoclit l . ), ipomoea grandifolia ( dammermann ) o &# 39 ; donnell , hairy merremia ( merremia aegyptia ( l .) urban ) or field bindweed ( convolvulus arvensis l . ); chenopodiaceae such as common lambsquarters ( chenopodium album l . ); portulacaceae such as common purslane ( portulaca oleracea l . ); amaranthaceae such as pigweed ( amaranthus spp .) ( such as prostrate pigweed ( amaranthus blitoides s . wats . ), livid amaranth ( amaranthus lividus l . ), purple amaranth ( amaranthus blitum l . ), smooth pigweed ( amaranthus hybridus l ., amaranthus patulus bertol . ), powell amaranth ( amaranthus powellii s . wats . ), slender amaranth ( amaranthus viridis l . ), palmer amaranth ( amaranthus palmeri s . wats . ), redroot pigweed ( amaranthus retroflexus l . ), tall waterhemp ( amaranthus tuberculatus ( moq .) sauer . ), common waterhemp ( amaranthus tamariscinus nutt . ), thorny amaranth ( amaranthus spinosus l . ), ataco ( amaranthus quitensis kunth .) or amaranthus rudis sauer . ); solanaceae such as black nightshade ( solanum nigrum l . ); polygonaceae such as spotted knotweed ( polygonum lapathifolium l .) or green smartweed ( polygonum scabrum moench ); cruciferae such as flexuous bittercress ( cardamine flexuosa with . ); cucuribitaceae such as burcucumber ( sicyos angulatus l . ); or commelinaceae such as common dayflower ( commelina communis l .). the herbicidal composition of the present invention is very useful in practical application . for example , the herbicidal composition of the present invention has a remarkable synergistic effect , and has a favorable herbicidal activity even if the doses of the respective compounds a and b are small , and accordingly the impact on the surrounding environment can be suppressed . further , the herbicidal composition of the present invention is capable of controlling cyperaceae such as purple nutsedge ( cyperus rotundus l .) or yellow nutsedge ( cyperus esculentus l . ); gramineae such as barnyardgrass ( echinochloa crus - galli l ., echinochloa oryzicola vasing . ), summergrass ( digitaria ciliaris ( retz .) koel ), large crabgrass ( digitaria sanguinalis l . ), shattercane ( sorghum bicolor ( l .) moench . ), wild oat ( avena fatua l . ), guinea grass ( panicum maximum jacq . ), signal grass ( brachiaria spp .) or bermudagrass ( cynodon dactylon pers . ); scrophulariaceae such as persian speedwell ( veronica persica poir . ); compositae such as hairy beggarticks ( bidens pilosa l .) or common ragweed ( ambrosia artemisiifolia l . ); leguminosae such as sunn - hemp ( crotalaria juncea l . ), rostrate sesbania ( sesbania rostrata bremek . & amp ; oberm .) or common lespedeza ( lespedeza striata ( thunb .) hook . et am . ); euphorbiaceae such as fireplant ( euphorbia heterophylla l . ); malvaceae such as velvetleaf ( abutilon theophrasti medic . ); convolvulaceae such as ivy - leaved morningglory ( ipomoea hederacea ( l .) jacq .) or field bindweed ( convolvulus arvensis l . ); or amaranthaceae such as redroot pigweed ( amaranthus retroflexus l . ), which are problematic as noxious weeds in agricultural fields such as upland fields and orchards , and non - cropland such as golf courses , railway sides and roadsides , in a wide application timing including before and after the emergence . further , it has a long lasting residual effect . further , since it comprises a combination of herbicides differing in the mode of action , it can control weeds having decreased sensitivity to many herbicides . in consideration of the application site of the herbicidal composition or the type or growth state of the undesired plants , the herbicidal composition of the present invention may be mixed with or may be used in combination with other herbicides , fungicides , antibiotics , plant hormones , insecticides , fertilizers , phytotoxicity - reducing agents , etc ., in addition to the above active ingredients , without departing from the intention and the scope of the present invention , whereby more excellent effects and activities may sometimes be obtained . such other herbicides may , for example , be ( 1 ) those which are believed to exhibit herbicidal effects by disturbing hormone activities of plants , ( 2 ) those which are believed to exhibit herbicidal effects by inhibiting photosynthesis of plants , ( 3 ) those which are believed to be converted to free radicals by themselves to form active oxygen in the plant body and show rapid herbicidal efficacy , ( 4 ) those which are believed to exhibit herbicidal effects by inhibiting chlorophyll biosynthesis of plants and abnormally accumulating a photosensitizing peroxide substance in the plant body , ( 5 ) those which are believed to exhibit herbicidal effects characterized by bleaching activities by inhibiting chromogenesis of plants such as carotenoids , ( 6 ) those which exhibit strong herbicidal effects specifically to gramineous plants , ( 7 ) those which are believed to exhibit herbicidal effects by inhibiting an amino acid biosynthesis of plants , ( 8 ) those which are believed to exhibit herbicidal effects by inhibiting cell mitoses of plants , ( 9 ) those which are believed to exhibit herbicidal effects by inhibiting protein biosynthesis or lipid biosynthesis of plants , and ( 10 ) those which are believed to exhibit herbicidal effects by being parasitic on plants . the herbicidal composition of the present invention may be prepared by mixing compound a and compound b , as active ingredients , with various agricultural additives in accordance with conventional formulation methods for agricultural chemicals , and applied in various formulations such as dusts , granules , water dispersible granules , wettable powders , tablets , pills , capsules ( including a formulation packaged by a water soluble film ), water - based suspensions , oil - based suspensions , microemulsions , suspoemulsions , water soluble powders , emulsifiable concentrates , soluble concentrates or pastes . it may be formed into any formulation which is commonly used in this field , so long as the object of the present invention is thereby met . at the time of the formulation , compound a and compound b may be mixed together for the formulation , or they may be separately formulated . the additives to be used for the formulation include , for example , a solid carrier such as kaolinite , sericite , diatomaceous earth , slaked lime , calcium carbonate , talc , white carbon , kaoline , bentonite , clay , sodium carbonate , sodium bicarbonate , mirabilite , zeolite or starch ; a solvent such as water , toluene , xylene , solvent naphtha , dioxane , dimethylsulfoxide , n , n - dimethylformamide , dimethylacetamide , n - methyl - 2 - pyrrolidone or an alcohol ; an anionic surfactant such as a salt of fatty acid , a benzoate , a polycarboxylate , a salt of alkylsulfuric acid ester , an alkyl sulfate , an alkylaryl sulfate , an alkyl diglycol ether sulfate , a salt of alcohol sulfuric acid ester , an alkyl sulfonate , an alkylaryl sulfonate , an aryl sulfonate , a lignin sulfonate , an alkyldiphenylether disulfonate , a polystyrene sulfonate , a salt of alkylphosphoric acid ester , an alkylaryl phosphate , a styrylaryl phosphate , a salt of polyoxyethylene alkyl ether sulfuric acid ester , a polyoxyethylene alkylaryl ether sulfate , a salt of polyoxyethylene alkylaryl ether sulfuric acid ester , a polyoxyethylene alkyl ether phosphate , a salt of polyoxyethylene alkylaryl phosphoric acid ester , a salt of polyoxyethylene aryl ether phosphoric acid ester , a naphthalene sulfonic acid condensed with formaldehyde or a salt of alkylnaphthalene sulfonic acid condensed with formaldehyde ; a nonionic surfactant such as a sorbitan fatty acid ester , a glycerin fatty acid ester , a fatty acid polyglyceride , a fatty acid alcohol polyglycol ether , acetylene glycol , acetylene alcohol , an oxyalkylene block polymer , a polyoxyethylene alkyl ether , a polyoxyethylene alkylaryl ether , a polyoxyethylene styrylaryl ether , a polyoxyethylene glycol alkyl ether , polyethylene glycol , a polyoxyethylene fatty acid ester , a polyoxyethylene sorbitan fatty acid ester , a polyoxyethylene glycerin fatty acid ester , a polyoxyethylene hydrogenated castor oil or a polyoxypropylene fatty acid ester ; and a vegetable oil or mineral oil such as olive oil , kapok oil , castor oil , palm oil , camellia oil , coconut oil , sesame oil , corn oil , rice bran oil , peanut oil , cottonseed oil , soybean oil , rapeseed oil , linseed oil , tung oil or liquid paraffins . these additives may suitably be selected for use alone or in combination as a mixture of two or more of them , so long as the object of the present invention is met . further , additives other than the above - mentioned may be suitably selected for use among those known in this field . for example , various additives commonly used , such as a filler , a thickener , an anti - settling agent , an anti - freezing agent , a dispersion stabilizer , a safener , an anti - mold agent , a bubble agent , a disintegrator and a binder , may be used . the mix ratio by weight of the active ingredients to such various additives in the herbicidal composition of the present invention may be from 0 . 001 : 99 . 999 to 95 : 5 , preferably from about 0 . 005 : 99 . 995 to about 90 : 10 . as a method of applying the herbicidal composition of the present invention , a proper method can be employed among various methods depending upon various conditions such as the application site , the type of the formulation , and the type and the growth stage of the undesired plants to be controlled , and for example , the following methods may be mentioned . 1 . compound a and compound b are mixed and formulated together , and the formulation is applied as it is . 2 . compound a and compound b are mixed and formulated together , and the formulation is diluted to a predetermined concentration with e . g . water , and as the case requires , a spreader ( such as a surfactant , a vegetable oil or a mineral oil ) is added for application . 3 . compound a and compound b are separately formulated , and the formulations are applied as they are . 4 . compound a and compound b are separately formulated , and as the case requires , the formulations are diluted to predetermined concentrations with e . g . water , and as the case requires , a spreader ( such as a surfactant , a vegetable oil or a mineral oil ) is added , and the formulations are applied . 5 . compound a and compound b are separately formulated , and the formulations are mixed when diluted to a predetermined concentration with e . g . water , and as the case requires , a spreader ( such as a surfactant , a vegetable oil or a mineral oil ) is added for application . preferred embodiments of the present invention will be described below , but the present invention is by no means restricted thereto . [ 1 ] a herbicidal composition comprising as active ingredients compound a and compound b . [ 2 ] the herbicidal composition according to [ 1 ], wherein the mixing ratio of compound a to compound b is from 1 : 0 . 2 to 1 : 50 by the weight ratio . [ 3 ] a method for controlling undesired plants or inhibiting their growth , which comprises applying a herbicidally effective amount of compound a and a herbicidally effective amount of compound b to the undesired plants or to a place where they grow . [ 4 ] the method according to [ 3 ], wherein compound a is applied in an amount of from 10 to 100 g / ha , and compound b is applied in an amount of from 20 to 500 g / ha . [ 5 ] the method according to [ 3 ] or [ 4 ], wherein the undesired plants are cyperaceae , gramineae , scrophulariaceae , compositae , leguminosae , euphorbiaceae , malvaceae , convolvulaceae or amaranthaceae . [ 6 ] the method according to [ 5 ], wherein the undesired plants are gramineae , scrophulariaceae , compositae , leguminosae , malvaceae or convolvulaceae . [ 7 ] the composition according to [ 1 ], wherein compound b is at least one member selected from the group consisting of imazapic , hexazinone and their salts . [ 8 ] the composition according to [ 1 ], wherein compound b is at least one member selected from the group consisting of imazapic , mesotrione and their salts . [ 9 ] the composition according to [ 1 ], wherein compound b is imazapic . [ 10 ] the composition according to [ 1 ], which contains flazasulfuron and imazapic in a mixing ratio of from 1 : 1 to 1 : 15 by the weight ratio . [ 11 ] the composition according to [ 1 ], wherein compound b is hexazinone . [ 12 ] the composition according to [ 1 ], which contains flazasulfuron and hexazinone in a mixing ratio of from 1 : 2 to 1 : 30 by the weight ratio . [ 13 ] the composition according to [ 1 ], wherein compound b is mesotrione . [ 14 ] the composition according to [ 1 ], which contains flazasulfuron and mesotrione in a mixing ratio of from 1 : 1 to 1 : 20 by the weight ratio . [ 15 ] the method according to [ 3 ], wherein flazasulfuron is applied in an amount of from 10 to 50 g / ha , and imazapic is applied in an amount of from 50 to 150 g / ha . [ 16 ] the method according to [ 15 ], wherein the undesired plants which are to be controlled or of which growth is to be inhibited , are gramineae , scrophulariaceae , compositae , leguminosae , malvaceae or convolvulaceae . [ 17 ] the method according to [ 16 ], wherein the undesired plants are summergrass ( digitaria ciliaris ( retz .) koel ), large crabgrass ( digitaria sanguinalis l . ), wild oat ( avena fatua l . ), persian speedwell ( veronica persica poir . ), common ragweed ( ambrosia artemisiifolia l . ), common lespedeza ( lespedeza striata ( thunb .) hook . et am . ), velvetleaf ( abutilon theophrasti medic .) or field bindweed ( convolvulus arvensis l .). [ 18 ] the method according to [ 3 ], wherein flazasulfuron is applied in an amount of from 10 to 50 g / ha , and hexazinone is applied in an amount of from100 to 300 g / ha . [ 19 ] the method according to [ 18 ], wherein the undesired plants are gramineae , scrophulariaceae , malvaceae or convolvulaceae . [ 20 ] the method according to [ 19 ], wherein the undesired plants are barnyardgrass ( echinochloa crus - galli l ., echinochloa orvzicola vasing . ), shattercane ( sorghum bicolor ( l .) moench . ), persian speedwell ( veronica persica poir . ), velvetleaf ( abutilon theophrasti medic . ), ivy - leaved morningglory ( ipomoea hederacea ( l .) jacq .) or field bindweed ( convolvulus arvensis l .). [ 21 ] the method according to [ 3 ], wherein flazasulfuron is applied in an amount of from 10 to 50 g / ha , and mesotrione is applied in an amount of from 50 to 200 g / ha . [ 22 ] the method according to [ 21 ], wherein the undesired plants are gramineae , leguminosae or convolvulaceae . [ 23 ] the method according to [ 22 ], wherein the undesired plants are wild oat ( avena fatua l . ), guinea grass ( panicum maximum jacq . ), rostrate sesbania ( sesbania rostrata bremek . & amp ; oberm .) or field bindweed ( convolvulus arvensis l .). [ 24 ] the composition according to [ 1 ], which contains flazasulfuron and mesotrione in a mixing ratio of from 1 : 3 to 1 : 20 by the weight ratio . [ 25 ] the method according to [ 3 ], wherein flazasulfuron is applied in an amount of from 10 to 30 g / ha , and mesotrione is applied in an amount of from 90 to 200 g / ha . now , the present invention will be described in further detail with reference to test examples . however , the present invention is by no means restricted to such specific test examples . in test examples , water dispersible granules containing flazasulfuron as an active ingredient ( tradename : shibagen df , manufactured by ishihara sangyo kaisha , ltd .) was used as flazasulfuron , a wettable powder containing imazapic ( manufactured by wako pure chemical industries , ltd .) prepared by a conventional method was used as imazapic , a wettable powder containing hexazinone ( manufactured by wako pure chemical industries , ltd .) prepared by a conventional method was used as hexazinone , and a flowable containing mesotrione as an active ingredient ( tradename : callisto , manufactured by syngenta ) was used as mesotrione . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of summergrass ( digitaria ciliaris ( retz .) koeler ) were sown . on the next day , predetermined amounts of flazasulfuron and imazapic were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 14th day after treatment , the state of growth of the summergrass was visually observed to determine the growth inhibition rate in accordance with the following evaluation standard . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) ( calculated value ) calculated by the colby &# 39 ; s formula are shown in table 1 . growth inhibition rate (%)= 0 ( equivalent to the non - treated area ) to 100 ( complete kill ) upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of ivy - leaved morningglory ( ipomoea hederacea ( l .) jacq .) were sown . on the next day , predetermined amounts of flazasulfuron and hexazinone were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 22nd day after treatment , the state of growth of the ivy - leaved morningglory was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 2 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of wild oat ( avena fatua l .) were sown . on the next day , predetermined amounts of flazasulfuron , mesotrione and imazapic were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 22nd day after treatment , the state of growth of the wild oat was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 3 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of guinea grass ( panicum maximum jacq .) were sown . on the next day , predetermined amounts of flazasulfuron and mesotrione were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 22nd day after treatment , the state of growth of the guinea grass was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 4 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of field bindweed ( convolvulus arvensis l .) were sown . on the next day , predetermined amounts of flazasulfuron and hexazinone were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 22nd day after treatment , the state of growth of the field bindweed was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 5 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of shattercane ( sorghum bicolor ( l .) moench .) were sown . on the next day , predetermined amounts of flazasulfuron and hexazinone were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 22nd day after treatment , the state of growth of the shattercane was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 6 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of rostrate sesbania ( sesbania rostrata bremek . & amp ; oberm .) were sown . on the next day , predetermined amounts of flazasulfuron and mesotrione were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 22nd day after treatment , the state of growth of the rostrate sesbania was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 7 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of persian speedwell ( veronica persica poir .) were sown . on the next day , predetermined amounts of flazasulfuron and imazapic were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 21st day after treatment , the state of growth of the persian speedwell was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 8 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of barnyardgrass ( echinochloa crus - galli l ) were sown . on the next day , predetermined amounts of flazasulfuron and hexazinone were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 21st day after treatment , the state of growth of the barnyardgrass was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 9 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of persian speedwell ( veronica persica poiret .) were sown . on the next day , predetermined amounts of flazasulfuron and hexazinone were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 21st day after treatment , the state of growth of the persian speedwell was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 10 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of common ragweed ( ambrosia artemisiifolia l .) were sown . on the next day , predetermined amounts of flazasulfuron and imazapic were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 21st day after treatment , the state of growth of the common ragweed was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 11 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of common lespedeza ( lespedeza striata ( thunb .) hook . et arn .) were sown . on the next day , predetermined amounts of flazasulfuron and imazapic were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 21st day after treatment , the state of growth of the common lespedeza was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 12 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of velvetleaf ( abutilon theophrasti medic .) were sown . on the next day , predetermined amounts of flazasulfuron and imazapic were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 21st day after treatment , the state of growth of the velvetleaf was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 13 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of velvetleaf ( abutilon theophrasti medic .) were sown . on the next day , predetermined amounts of flazasulfuron and hexazinone were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 21st day after treatment , the state of growth of the velvetleaf was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 14 . upland field soil was put into a 1 / 160 , 000 ha pot , and seeds of field bindweed ( convolvulus arvensis l .) were sown . on the next day , predetermined amounts of flazasulfuron , mesotrione and imazapic were diluted with water ( in an amount corresponding to 300 l / ha ), and applied for soil treatment by a small sprayer . on the 21st day after treatment , the state of growth of the field bindweed was visually observed to determine the growth inhibition rate . the growth inhibition rate (%) ( measured value ) and the growth inhibition rate (%) calculated in the same manner as in test example 1 are shown in table 15 .
at present , many herbicidal compositions have been developed and used , but they are not necessarily sufficient to control undesired plants such as weeds to be controlled in some cases , and a herbicidal composition having high activity has been desired . a herbicidal composition comprising flazasulfuron or its salt , and at least one herbicidal compound selected from the group consisting of imazapic , hexazinone , mesotrione and their salts , and a method for controlling undesired plants using it .