## 3 Results
### GPP, Reco, and NEE Fluxes
#### 3.2.1 Gross Primary Production (GPP)  
Analyzing the daily flux rates in the individual meadow cut, a direct influence of meteorological conditions on their magnitude can be observed (Figure 4). Concerning GPP, it is noticeable that in 2021 the highest fluxes were reached during the second cut (1.06-14.07.21), with the average daily fluxes up to \(-\)14.75 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for HWL, \(-\)20.37 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for HWL, \(-\)17.36 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for LWL and \(-\)14.07 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for LWL.Si. Values in the I and III cuts were similar to each other, and their average daily values ranged from \(-\)6.24 to \(-\)9.24 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\), depending on the plot. The average daily GPP fluxes for the entire growing season in 2021 were \(-\)7.99 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for HWL, \(-\)9.20 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for HWL,Si, \(-\)7.97 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for LWL and \(-\)7.15 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) for LWL.Si. In the 2022 growing season, daily GPP rates were higher for plots with higher WTD and ranged from \(-\)9.40 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) at the HWL to \(-\)10.16 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) at the HWL.Si, whereas at plots with lower WTD, GPP fluxes were at the rates similar to those in 2021 and ranged from \(-\)7.41 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) at the LWL to \(-\)8.00 gCO\({}_{2}\)-C\(\cdot\)m\({}^{-2}\)\(\cdot\)day\({}^{-1}\) at the LWL.Si plots. Looking at the distribution of daily GPP rates in the individual cuts in the second year of the study, it can be seen that the highest fluxes were reached in the first cut and not in the second cut like in the previous year. Therefore, the seasonal distribution of fluxes is different from the first year of the study, which was influenced by different meteorological conditions. Statistical analyses were carried out to check whether the differences in daily GPP rates between treatments in each cut were significant. Due to the lack of a normal distribution of daily GPP values, a non-parametric Wilcoxon matched-pairs test was performed. Figure 5 shows the results obtained from the analysis. For all \(p<\) 0.05, the null hypothesis of no significant difference between the values was rejected. Therefore, it can be concluded that in the I, II, and III cuts in 2022, and also in the I cut in 2021, the daily GPP rates for individual plots differ significantly. In the case of the II cut in 2021, no significant differences were observed between the LWL.Si and HWL plots, and in the III cut in 2021, between LWL and LWL.Si. The resultsshow that WTD significantly impacted the daily GPP fluxes. Furthermore, the application of silicon antitranspirant also significantly affected the daily GPP rates. This was evident for plots with higher and lower WTD in all cuts except for the third cut in 2021, wherein no significant differences were observed between the LWL and LWL_Si plots. Figure 3: The seasonal dynamics of modeled daily rates of **(a)** GPP; **(b)** Reco; and **(c)** NEE fluxes for control (HWL, LWL) and treated plots (HWL_Si, LWL_Si); grey background marks the growing season. Figure 4: Daily GPP fluxes for each plot per cut and growing season (**a**) in 2021; (**b**) in 2022. Figure 5: Comparison of daily GPP fluxes for individual plots (HWL, HWL_Si, LWL, LWL_Si) using Wilcoxon matched-pairs test in each cut in 2021 and 2022. \(p<0.05\) means that the pairs are significantly different from each other. Figure 6 shows the cumulative GPP values in each cut. During the two-year study period, the highest uptake for each plot was recorded in the first cut of 2022.