## 3 Results  
On average, across growing seasons, crude fiber content in plants on plots where slurry was applied together with the UGmax and Humus Active soil conditioners was slightly smaller (approximately 1.6 and 3.4%, respectively) than in plants treated with slurry on its own. The biomass from plots treated with slurry with the addition of mineral fertilizers contained more than 3% of crude fiber compared to the plants treated with slurry only. Crude fiber content in _Festulolium braunii_ (Table 3) significantly varied only across harvests. There was a 2-5% decrease, average of growing seasons, in crude fiber content in plants from the first harvest on plots treated with slurry combined with soil conditioners and slurry supplemented with mineral fertilizers. A different response to the same treatment was observed in the second harvest. The combination of slurry with soil conditioners slightly increased fiber content, but when used together with mineral fertilizers it increased the content by 7% compared to plots where slurry was used on its own. Slurry supplemented with the UGmax and Humus Active soil conditioners reduced raw fiber content by 4.5 and 6.5% (average of the experiment), respectively, compared to slurry used together with mineral fertilizers. On average the highest crude fiber content was in the grass of the second harvest and the smallest in the first. The content was higher (by 4%) in the first year than in the second. The content of neutral detergent fiber in _Festulolium braunii_ significantly varied depending on the treatment (Table 4). At the same time, according to statistical analysis, the interaction between treatments and growing seasons had a significant impact on this content. The largest NDF content, average of growing seasons, was in plants treated with slurry combined with UGmax, about 10% higher than on plots with slurry alone. The combined application of the Humus Active soil conditioner resulted in approximately 7% higher content of NDF in _Festulolium braunii_ than when it was treated with slurry only. Plants treated with slurry supplemented with mineral fertilizers contained 4% of NDF more than those treated with slurry only. The interaction of slurry with UGmax and Humus Active soil conditioners also increased NDF content by 2.6 and 5.2%, respectively, compared to the effect of slurry supplemented with mineral fertilizers. In individual harvests, the most NDF fraction was also recorded in the biomass from plots treated with slurry supplemented with the UGmax soil conditioner. In the second harvest in the biomass from the same plots a 12% increase in comparison to the plants treated with slurry only was reported. On average, the largest content was found in the second harvest, the smallest in the third. NDF content was higher in the first year than in second. The amounts of ADF in _Festulolium braunii_ were significantly different in both growing seasons, higher in the second one than in the first (Table 5). In addition, there was a significant interaction between treatments and growing seasons, affecting the content of this fiber fraction. Across treatments, the largest ADF content was found in the plants treated with slurry only, however combining slurry with soil conditioners resulted in its reduction (for UGmax by 8%, for Humus Active by 12.0%). NPK fertilizers reduced it by 9.0% compared to plants treated with slurry; the analysis of harvests across the growing seasons showed a similar dependence. There were no significant differences between ADF fiber content in _Festulolium braunii_ treated with slurry combined with soil conditioners and in plants treated with slurry supplemented with NPK mineral fertilizers. The greatest amount of the ADF fraction in _Festulolium braunii_ was in the third harvest of 2017, but, on average, over growing seasons its lowest amounts were in the plants of the third one, with the largest in the second. The content of acid detergent lignin in the plants did not significantly vary across experimental factors (Table 6).