## 3 Results and Discussion
### Soil Density and Total Porosity  
Experimental research has shown that continuous treatment of the same soil with biopreparations for two years on average increased the total porosity of the soil in 2017 by about 6.49% compared to 2016, except for Treatment 7 (Table 2). It was found that, after exposure to different biopreparations and their mixtures, in the first year after the whole vegetation period, the total porosity of the soil increased by, on average, 0.30 to 12.20%, and in the second year--by 4.20-8.40% compared to the control. A higher average increase in total soil porosity was observed in the second year (approximately 7.60%) compared to the first year (5.37%) of the research. Comparing the results of 2016 and 2017 between the same treatments it has been established that an increase in the total soil porosity was significantly higher in Treatment 1, Treatment 2, Treatment 4, and Treatment 6 in 2017. Other researchers also claim that an exposure of soil to biopreparations has a positive effect on soil physical properties and observe an increased in soil porosity [50; 58]. Improving the physical properties of the soil has a positive impact not only on one technological operation, but on the successful management of the whole agriculture, as well [22].  
Our analysis of the experimental research results showed that the soil density decreased on average by 0.09 g cm\({}^{-3}\) in 2017 compared to 2016. A decrease in soil density from 0.04 to 0.19 g cm\({}^{-3}\) was observed in all treatments with biopreparations in the first year, and from 0.01 to 0.15 g cm\({}^{-3}\) in the second year of the experimental research, compared to the control treatment without biopreparations. Comparison of soil density between the same treatments in different years revealed a significant decrease in soil density in 2017 in all treatments except for Treatment 7. Soil density was especially small (approximately 1085 g cm\({}^{-3}\)) in 2017 in a Treatment 1 and Treatment 2. In addition to the effect of biopreparations on soil density, different precipitation rates in July and August before shallow tillage may also have had an influence. Other researchers have reported that water content in soil affects soil density [24; 59; 60].  
Figure 6: Decrease in the traction force of the shallow tillage machine (%) in different treatments in 2017 compared to the more humid year 2016: Treatment 1—composition of Table 1. Treatment 2—No. 1 and No. 2 mixture; Treatment 3—composition of the biopreparation No. 2; Treatment 4—No. 1 and No. 3 mixture; Treatment 5—composition of the biopreparation No. 4; Treatment 6—No. 1 and No. 4 mixture; Treatment 7—composition of the biopreparation No. 3.  
Summarizing the results of soil density and total soil porosity, it can be concluded that, in spring, when plant vegetation is renewed, the use of biopreparations can strongly affect these soil properties, having a positive effect on the reduction of machine traction force during shallow tillage. Previous researchers have also found that biopreparations not only affect plant productivity and improve soil microbiological status but alter soil physical and chemical properties, as well [61; 62]. Exposure of soil to nutrient-based biopreparations can increase the content of organic carbon in the soil and affect soil structure, porosity, and density. Changes in organic waste can maintain or increase the content of soil organic carbon, soil porosity, and decrease soil density [50; 63].