## 3 Results
### Meadow Yield
same situation occurred in 2022, when higher groundwater levels contributed to the annual biomass yield being higher by 11.7%, with 10,030.97 kg\(\cdot\)ha\({}^{-1}\) and 8978.55 kg\(\cdot\)ha\({}^{-1}\) from the HWL and LWL plots, respectively. Analyzing the individual cuts in both years, a continuing trend can be seen--the dry matter yield from the HWL plot was higher than that from LWL for almost all the cuts. The exception is the first cut in 2021, when a higher yield was obtained from the LWL plot. This is most likely due to too-high soil moisture at HWL, which was a limiting factor for plant development. High soil moisture (close to the maximum field water capacity) results in water saturation of the soil pores, causing a concomitant oxygen deficiency in the soil, which can inhibit plant growth and development [30]. Furthermore, when analyzing both years, it is noticeable that considerably higher yields were obtained in 2021 than in 2022. For the HWL plot, these amounted to 12,693.04 kg\(\cdot\)ha\({}^{-1}\), whereas in the following year, it was 10,030.97 kg\(\cdot\)ha\({}^{-1}\), i.e., a decrease of 21.0%. A similar trend was observed in the other plots. On HWL_Si, yields in 2022 decreased from 10,429.13 kg\(\cdot\)ha\({}^{-1}\) (2021) to 8293.92 kg\(\cdot\)ha\({}^{-1}\) (20.5% reduction). The largest difference between the years occurred in the LWL plot, where yields in 2022 were 25.5% lower than in 2021 (reduction from 12,047.61 to 8978.55 kg\(\cdot\)ha\({}^{-1}\)). In the case of LWL_Si, the yield reduction was at the level of 23.0%; from 10,364.24 kg\(\cdot\)ha\({}^{-1}\) to 7978.25 kg\(\cdot\)ha\({}^{-1}\). The obtained differences in yields directly reflect the values of GPP, which depended, among other things, on the different meteorological conditions in both years. Although the year 2022 was warmer and had higher precipitation, the average values of soil moisture in the growing season were lower, which could be indirectly reflected in the obtained yields, which were lower than in the previous year. When the individual cuts are examined, it can be observed that similar amounts of dry matter were harvested from the first cut in 2021 and 2022. Furthermore, all plots apart from LWL had even higher yields in 2022 than in 2021, so the trend in this cut was the opposite of that for the rest of the year. A definite yield reduction between years was already visible during the second cut. This ranged from 21.6% (863.94 kg\(\cdot\)ha\({}^{-1}\)) for the HWL_Si plot to as much as 32.1% (1282.67 kg\(\cdot\)ha\({}^{-1}\)) for the LWL plot. This yield reduction corresponds to one of the driest periods with the lowest soil moisture, which decreased by up to 18% and 16% at the HWL_Si and LWL_Si plots, respectively (Table 1). In comparison, the soil moisture of the same plots in the second cut of 2021 reached 47% and 42% for the HWL_Si and LWL_Si plots, respectively. Therefore, the topsoil in the second cut of 2022 was over-dried, resulting in suboptimal plant development conditions. Furthermore, the second cut in 2022 lasted longer (70 days) than in 2021 (44 days), and thus covered the period with the lowest groundwater levels. Moreover, the unfavorable rainfall distribution during the growing season also affected the results. For example, in August 2022, the total rainfall was 135 mm, of which as much as 83 mm fell on a single day--20 August. The third cut of 2021 was shorter by 16 days and, above all, covered an earlier period--the final cut took place more than a month earlier (30.09.2021) than in 2022 (17.11.2022). This directly resulted in a higher average daily temperature of 16.8 \({}^{\circ}\)C in 2021 in the third cut, and one of only 12.9 \({}^{\circ}\)C in 2022. Concerning the entire growing season, the average soil moisture was 12% lower in 2022 for the plots with high groundwater levels (47% in 2021 vs. 35% in 2022) and 10% lower for the plots with lower groundwater levels (41% in 2021 vs. only 31% in 2022).