INFLUENCE OF THE AZOSPIRILLUM INOCULATION MODEL ON GRASS PERFORMANCE

Through four glasshouse experiments using random block designs with 5 and 7 replications the influence of the type of inoculum, dosage,vehic le and: Azospirillum inoculation time on grass performance was studied . In the first experiment the Sorghum bicolor treated with bacteria at intervals of 7 to 21 days did not increase yields. In the second expe riment the sorghum with two inoculant dosages increased aerial yield ( 1.75 to 2.00 g/plant) in respect to the control (1.46 g/plant) but it was higher with the lowest dosage. In the third experiment guinea gras s treated with bacteria concentrations from 10(7) to 10(4) did not inf luence aerial biomass but radical biomass with the former (0.93 g/plan t) surpassing the remaining treatments (0.52 to 0.77 g/plant). In the first cut of this experiment lowest N yields were found in the control (4.01 mg/plant) which did not differ from the treatment with 10(3) cf u ml(-1) (456 mg/plant) compared to the remaining treatments (5.07 to 5.57 mg/plant). In the second cut the inoculation with 10(6) cfu ml(-1 ) (9.71 mg/plant) significantly surpassed the remaining treatments (7. 40 to 8.79 mg/plant). In the last experiment the treatment with bacter ial broth recorded the highest aerial and radical guinea grass accumul ated (3.73 and 1.35 g/plant, respectively) surpassing the control (3.1 5 to 0.98 g/plant in each cut respectively). In the first cut, the hig hest N yields were found in the treatment with broth and unfertilized peat (15.94 to 16.37 mg/plant). In the second cut, peat treatments (10 .02 to 11.36 mg/plant) surpassed the control (11.81 and 7.96 mg/plant in the first and second cut, respectively). Sorghum did not show respo nse in aerial yield at inoculation time, but it did in the inoculant d osage which was more effective with the lowest dosage, but had no effe ct on the radical system of this plant. Guinea grass treated with diff erent bacteria concentrations did not increase in aerial biomass, but it increased the radical weight with 10(7) cfu ml(-1). On testing diff erent types of inoculants, the highest responses were found with bacte rial broth. These results justify further studies to improve the respo nses found.