EFFICIENCY OF COMMERCIAL INOCULANTS FOR SOYBEAN

To reach high soybean yields, it is suitable to use inoculats, especially in those growing areas where soils do not contain native populations of appropriate rhizobia or where their occurrence is limited. To observe growth and yields of soybean treated by different commercial inoculants, was the object of this paper. Pot vegetation experiment with soil, as well as field experiment, were carried m. The influence of different irrigation doses upon soybean growth and yield was established in both types of experiments. Five commercial inoculants (originating in the USA, Great Britain, France, Austria and the Czech Republic) were used in the experiment. Before starting the experiments, their quality was tested from the point of view of rhizobial cells quantity in 1 g of inoculant, as well as from that of their microbial purity. For control, non-inoculated variants were found. Inoculation was done by mixing moistured seed with appropriate quantity of inoculant close to sowing. The Czech variety Polanka was used in the experiment. Nodulation, as well as the number, weight and nitrogenase activity of nodulated roots, were observed during the plant vegetation. In the moment of full ripeness yield parameters and their structures were observed. During seed inoculation 10(5) to 10(6) Bradyrhizobium japonicum cells were added to each seed. This quantity is considered as minimal necessary for the inoculation effect to be evident. Relatively balanced bradyrhizobia cells quantities formed significantly distinguished numbers of nodules per plant in dependence to the inoculant used, but no significant differences were found in the plant biomass. Limited irrigation significantly reduced the nodule formation, their weight and nitrogenase activity with all the inoculants. The seed yield too was highly reduced at limited irrigation. Seed yield was dependent mainly on pod spreading on the plant and on their weight. Significant differences were found in inoculants as far as the seed yield is concerned, application of each inoculant oculant increased the soybean seed yield above the level of the untreated variant. Some significant influences of interactions inoculation x irrigation were found.