Soybean (Glycine max L. Merrill) is an oleiferous plant, which belongs to the papilionaceous group (Fabaceae). It is classified as an annual plant whose grain is rich in proteins (about 40%) and fats (about 20%). Soybean is an important papilionaceous plant as it binds the aerial nitrogen in roots nodules by the help of the symbiotic bacteria Rhizobium japonicum in Bradyrhizobium japonicum and this contributes to the balance of nitrogen in the crop rotation. Zeolites are rocks of volcanic origin, which were formed 30 million years ago by the mixing of volcanic lava, seawater and ash. Because the zeolite flour enriches soil with minerals, preserves water and helps plants to survive through the periods of drought, we decided to use it in the block field experiment with the 'ES Mentor' soybean variety on the premises of the Biotechnical Faculty in Ljubljana. During the soybean growth stage, we conducted the analysis of nodulation using 160 plants in different treatments. The most nodules (154) were counted when conducting the experiment without the zeolite flour. As the height of the plant to its first pod plays an important factor during the mechanical harvest, we discovered that the pods were located heighest on the plants when the experiment involved zeolite flour in the soil and when soya was fertilized by mineral nitrogen during the stage of bloom. The largest yield per hectare, i.e. 3.3 t/ha at the 9 % seed moisture was also harvested on the plots where the zeolite flour (600 kg/ha) and mineral nitrogen (30 kg/ha) had been added. Because we cannot entirely confirm the positive impact of the zeolite on the harvest and also some other aspects pertaining to the harvest, we suggest the repetition of the experiment in different growth conditions.
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