Soybean Rizobia Inoculation Has a Positive Contribution to Argentine Grain Production.

In Argentina, the request of microbiological products that enhances crop nutrition and growth is increasing. It is estimated that approximately 70% of the soybean crops are inoculated with rizobia providing not only better N nutrition but also greater grain yields. The objective of the study was to quantify the contribution of the present use of Bradyrhizobium japonicum on soybean production in soybean rotated lands. During the 2007/8 and 2008/9, 28 experimental sites were established comparing untreated control and seed inoculated treatments using a single experimental formulation the National Institute of Agricultural Technology (INTA) providing more than 10⁵ units of rizobia forming colonies by soybean seed. In each location, the nodulation (number and dry weight) was evaluated at v4 and r5 growing stages, the shoot dry matter at r6 and grain production and yield components (single grain weight) at physiological maturity. The N derived from the biological N fixation process was also evaluated using the natural ¹⁵N abundance method. In each site the experimental design was completely randomize block with 4 replications and plots with 5 rows of 5 m in length and distanced 0.52 m each. The results showed greater nodule biomass and grain yields in the inoculated crops. The mean grain yields of the inoculated crops relative to the control without inoculation varied between 8 and 11% in the 2008/9 and the 2007/8 growing seasons, respectively. These results confirm the generalized recommendation of the application of rizobia containing inoculants for soybean production in rotated lands.