## 5 Conclusions  
The impacts of subirrigation and silicon antitranspirant application, as well as meteorological conditions, on the net carbon balance of the three-cut meadow was different for individual seasons and years, although some significant and conclusive statements can be formulated.  
1. In the drier and colder year (2021), net CO\({}_{2}\) emissions predominated, whereas net CO\({}_{2}\) assimilation predominated in the warmer and wetter year (2022) for all the plots, which highlights the impact of meteorological conditions on the annual NEE of grasslands.
2. Higher WTD and higher soil moisture promote CO\({}_{2}\) emissions from the meadow (Reco is higher), most probably due to an increase in the autotrophic respiration of plants due to higher aboveground biomass.
3. Higher WTD and higher soil moisture promote higher yields of aboveground biomass. The yields were higher by 5.4% (in 2021) up to 11.7% (in 2022) at plot with a higher WTD, which highlights the role of the WTD in maintaining high production in meadows.
4. Silicon antitranspirant application has a positive impact on meadow productivity (GPP), but only on plots with higher WTD.
5. Silicon antitranspirant application has a negative impact on the yield of aboveground biomass (reduction of annual yield from 11.1% to 17.8%). The reduction of yield is higher at the plot with a higher WTD.
6. The yield at which the meadow turns from being a net source to a net sink of CO\({}_{2}\) in single cuts shifts from around 3800 kg\(\cdot\)ha\({}^{-1}\) at plots without silicon antitranspirant application to 3200 kg\(\cdot\)ha\({}^{-1}\) at treated plots, while cumulated NEE is more negative at the same biomass yield for plots with silicon application. It indicates that silicon antitranspirant application may have a positive effect on improving the carbon balance of meadows (either by reducing net emissions or increasing net assimilations).  
Although some findings presented in this study are not unequivocal, the obtained results increase our understanding and the current state-of-the-art knowledge about the use of antitranspirants and subirrigation management systems in meadows, and we believe it will stimulate new studies in the future.  
**Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/w15173057/s1](https://www.mdpi.com/article/10.3390/w15173057/s1)]([https://www.mdpi.com/article/10.3390/w15173057/s1](https://www.mdpi.com/article/10.3390/w15173057/s1)), Figure S1: Spearman correlation matrix for daily values of GPP, RECO, NEE, soil moisture (SM), air temperature (TA), and water table depth (WTD) in 2021 for individual measurement plots: (a) HWL; (b) HWL_Si; (c) LWL; (d) LWL_Si.; Figure S2: Spearman correlation matrix for daily values for daily values of GPP, Reco, NEE, soil moisture (SM), air temperature (TA), and water table depth (WTD) in 2022 for individual measurement plots: (a) HWL; (b) HWL_Si; (c) LWL; (d) LWL_Si.  
**Author Contributions:** Conceptualization, J.K., M.S., R.J. and D.L.; methodology, R.J.; M.S. and J.K.; validation, M.S., R.J. and J.K.; formal analysis, J.K., M.S. and R.J.; investigation, J.K., D.L. and M.S.; resources, R.J. and M.S.; data curation, M.S., R.J. and J.K. writing--original draft preparation, J.K., writing--review and editing, M.S., R.J., D.L. and J.K.; visualization, J.K. and M.S.; supervision, M.S., R.J. and D.L.; project administration, J.K. and D.L.; funding acquisition, J.K. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported by the Discipline of Science Environmental Engineering, Mining and Energy in Poznan University of Life Sciences (Poland) as the research program \"Innovator\", no. 01/2022/INN.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.