*2.3. Experimental Design*

The study was conducted in a pot experiment, at the teaching-experimental station of the University of Warmia and Mazury in Olsztyn (NE Poland, 53.760◦ N 20.454◦ E). It was accomplished in two series: with nonsown (without grasses) soil and with soil sown with the selected grass species. The experiment (pots sown with six different species of grass and soil without grasses) was performed in four replications in 10 dm<sup>3</sup> Kick–Brauckman pots, each filled with 9 kg of soil. Before the experiment had been established, the soil was sieved through a screen with mesh diameter of 5 mm, then thoroughly mixed, weighed into 9-kg portions, carefully mixed with mineral fertilizers, and poured into the pots. With soil sowing, 22 seeds were sown to each pot. The same mineral fertilization was applied for all grass species and control soil (not sown with grasses). The pre-sowing fertilization included, in mg kg−<sup>1</sup> soil d.m. (dry matter): N—80, P—20, K—40, and Mg—10, whereas, after the harvest of the first and the second re-growth, the plants were additionally fertilized with nitrogen in the amount of 40 mg N kg−<sup>1</sup> soil d.m.. All grass species emerged evenly and at the same time. After emergence, 20 plants were left in each pot. The experiment spanned for 105 days. Within this period, soil humidity was kept at a level of 50% of the maximum water capacity. The grasses were cut three times. Each time,

the biomass of aerial parts was determined. In the last term of cutting (day 105 of experiment). Plants were removed from the pots and then the soil from each pot was mixed thoroughly.
