the invention is carried out using bacteria of the rhizobium and bradyrhizobium genus , which are capable of forming nodules in the roots of one or more species of leguminous plants . preferred strains include bradyrhizobium japonicum , rhizobium meliloti , rhizobium leguminosarum biovar trifolii , rhizobium leguminosarum biovar viceae and rhizobium leguminosarum biovar phaseoli . the selection of rhizobium and bradyrhizobium strains effective for nitrogen fixation is a first necessary step for producing a high quality leguminous seed inoculant . specificity of effectiveness is expressed as differences in action between species and differences among the species . ecological factors should be also taken into account , such as competitive capacity for growing in the soil and in the rhizosphere , competitive ability for forming nodules and surviving in both , presence and absence of the plant . other factors to be taken into account for selecting a microbial culture are tolerance to carrier means , tolerance to the substrate where it is applied and soil features . after the desired rhiozobian strain is selected , it is cultured in a growth medium within a conventional fermenter . a suitable growth medium can be , for instance , an aqueous medium having saccharose , yeast autolysate , potassium phosphate , magnesium phosphate heptahydrate , calcium chloride and ferrous chloride . fermentation is conducted preferably under shaking at about 30 ° c ., till a high bacteria concentration is achieved . for practicing the inventive inoculating composition , shares of the fresh bacterial culture having viable cells are mixed with equal shares of a sterilized suspension containing a molybdenum compound and a polymer of the type presenting an amide , amine or imine moiety , such as polyvinyl pirrolidone . viable cells concentration used is that necessary for obtaining a concentration in the final composition of the invention of about 5 . 0 × 10 9 bacteria / ml . polymers having an amidic nitrogen may be those of the type having sub - units carrying a 2 - pirrolidone cycle , such as polyvinyl pirrolidone ( pvp ), polymers of alkylated vinyl pirrolidone , vinyl pirrolidone / vinyl acetate , styrene and substituted derivatives copolymers . preferably , pvp k - 60 is used , such as luviskol k60 by basf . also alkylated vinyl pirrolidone polymers may be used ( agrimer al , furnished by international speciality products ). a suitable range for concentration of pvp and the like in the inoculating composition of present invention may be about 0 . 2 and 5 % weight / weight . preferably . a 3 % weight / weight concentration is used . the suspension also contains suitable adjuvants that provide for stability into the final composition . as such adjuvants , stabilizers may be used such as carboxymethyl cellulose , arabic gum , sodium alginate and the like . preferably , sodium alginate is used in concentration ranging from 0 . 1 to 1 %, more preferably about 5 %. preferably , also carboxymethyl cellulose is used in a concentration of about 0 . 5 and 2 %, more preferably at about 1 %. furthermore , the composition may contain nutrients or growth factors , such as sugars , aminoacids , proteins , salts , and the like . additionally , the composition may contain osmoregulating agents , buffers , etc . the inoculating composition of the invention may be stored at room temperature for about two years , the bacteria survival being guaranteed . the inventive aqueous composition may be stored in 250 ml plastic bags , which are sterilized before filling and sealed after filling . coating of seeds may be performed by spraying or simply mixing the aqueous composition with the seeds in a hopper or suitable container till a uniform seed coating is achieved . the inoculant / seed proportion can be about 150 cm 3 of the inoculating composition per 50 kilograms of seeds . the invention has been generally described , and will be better understood when taken in reference to certain non limiting examples , which are included only for illustrative purposes . a single colony of bradyrhizobium japonicum was sown in 100 ml of a culture medium ( 1 % of saccharose , 0 . 05 % of yeast autolysate , 0 . 022 % of k 2 hpo 4 , 0 . 01 % of mgso 4 . 7h 2 o , 0 . 004 % of cacl 2 and 0 . 002 % of fecl 3 in water ). it was incubated for 7 days at 30 ° c . in a rotary shaker at 120 rpm . the process was repeated bringing the 100 ml to 1 liter of fresh medium , and fermenting again . 1000 ml of the obtained culture were mixed with 1000 ml of a sterilized cooled solution , prepared from the dissolution in water of 0 . 5 % of sodium alginate , 1 % of carboxymethyl cellulose , 3 of polyvinyl pirrolidone and 0 . 2 % of k 2 moo 4 . the mixture was packed under sterilized conditions in previously sterilized 250 cm 3 plastic bags . samples of the composition prepared according to example 1 were stored for 720 days . periodically , a sample was extracted and viability was determined , and cell counting performed , the initial composition concentration ( time 0 ) being of 5 . 0 × 10 9 colony forming units / ml ( cfu / ml ). the results are shown in fig1 . analysis of the curve obtained shows that the aqueous inoculating composition keeps viability of b . japonicum over 10 8 cfu / ml for the 720 th day and is above 10 9 cfu / ml for the first 300 days . two kilograms of soybean seeds were inoculated with the composition obtained according to the description in example 1 . the inoculation was made by mixing the inoculating composition with the seeds in a bag or waterproof canvas till an even coating over the seeds was achieved . a proportion of inoculant / seed similar to that determined for a field sowing was used , i . e . about 150 cm 3 inoculant / 50 kg of seeds . a similar process was used for a control lot , with an inoculant without pvp / mo . periodically , 50 seeds from each formulation were taken each time , placed in a beaker whereto 100 ml of physiological solution was added . through shaking , bacteria initially stuck to the seed cuticle passed onto the solution . sowing was made and counting of bacteria was performed and number of bacteria per seeds ( or colony forming units / seed , cfu / seed ) was calculated . this process was repeated at 8 , 24 , 48 , 168 and 336 hours . essay temperature was 30 ° c . results are shown in table 1 below . results of this experience show that addition of pvp to the inoculant composition provides a higher number of viable bacteria present in the seed coating , which remained over 10 4 , even when the control group no longer provided viable bacteria ( 336 hours ). an essay was conducted following general process explained in example 3 , but from inocules with different bacteria concentrations . results follow in table 2 and fig2 . from representation of data of fig2 it is clearly seen that addition of pvp to the inoculating composition provides a longer persistence to the bacteria on the seed coating . in fact , drop in the counting is only by two orders of magnitude after 336 hours have elapsed , while using an inoculant without pvp , bacterial persistence is seriously affected , counting dropped by five orders of magnitude , just to 1 ufc / seed after 336 hours . two kilograms of soybean seeds were inoculated with the composition obtained according to the description in example 1 . the inoculation was made by mixing the inoculating composition with the seeds in a bag or waterproof canvas till an even coating over the seeds was achieved . a proportion of inoculant / seed similar to that determined for a field sowing was used , i . e . about 150 cm 3 inoculant / 50 kg of seeds . a similar process was used for a control lot , with a similar inoculant , but without pvp / mo . 150 beakers with sterilized vermiculite were prepared . sowing was as follows : 50 beakers with an inoculant - free seed ( negative reference ) each , 50 beakers with a seed inoculated with a pvp / mo - free , aqueous composition ( control inoculant ), and 50 beakers with a seed each , inoculated with the composition with pvp / mo , prepared according to the description of example 1 . light : photoperiod 16 / 8 ; light source : ceiling covered with daylight tubes and gro - lux in a 2 : 1 ratio , placed at about 40 - cm height from the beaker edges . intensity on the edge of the beaker was about 4600 lux . beakers were irrigated with a jensen solution ( 2 ml of 10 % k 2 hpo 4 , 5 ml of 4 % mgso 4 . 7h 2 o , 10 ml of 2 % nacl , 0 . 1 ml of 10 % fecl 3 , 1 g of cahpo 4 in 1 liter of sterilized distilled water , with a final ph of 6 . 9 ), diluted at 25 %. after a week , some observations were made , little nodules were detected in the roots of the plants treated with the inoculant of pvp / mo , while in the negative reference plants and in the control plants no nodule was detected . a week later , all seeding were removed . the number of plants was recorded as well as the number of nodules per plant . the results are shown in table 3 below . mention should be made that 100 % of the plants treated with the inventive inoculant reach an average of 10 . 03 well - sized nodules per plant in the root crown . 81 . 25 % of the plants treated with the control inoculant reach an average of 5 . 64 nodules , but of smaller size , per plant . plants without inoculant coating ( negative reference ) developed no nodule whatsoever .
an aqueous - based inoculant composition in liquid form for leguminous seeds that produces an immediate nodule formation and an increased nitrogen fixation , containing microorganisms of the rhizobium or bradyrhizobium genus , a molybdenum compound selected from alkali metal molybdates and a compound that neutralizes the seed exudates , which are toxic for the bacteria , selected from polymers of compounds presenting an amide , amine or imine moiety . the inoculant composition remains stable at room temperature , keeping the number of viable bacteria over long periods of time and ready to be used .