## 5 Conclusions  
A static chamber with a portable CO\({}_{2}\) analyzer was designed and implemented. It is an economical, simple, and effective alternative to traditional NEE calculation methods. It  
Figure 12: Determination coefficients between NEE values (\(\mu\)molCO2 m\({}^{2}\) s\({}^{-1}\)) calculated with the portable analyzer and EC by [PERSON] et al. [11], [PERSON] et al. [12] & [PERSON] et al. [13]; respectively.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**References**} & \multicolumn{2}{c}{**Tillering**} & \multicolumn{2}{c}{**Floral Primorium**} & \multicolumn{2}{c}{**Spindle State**} & \multicolumn{1}{c}{**Bloom**} \\ \cline{2-7}  & **82 DPS** & **89 DDS** & **102 DPS** & **111 DPS** & **126 DPS** \\ \hline [PERSON] et al. [11] & 96 ** & 98 ** & 99 ** & 88 ** & 90 ** \\ [PERSON] et al. [12] & 83 ** & 85 ** & 75 ** & 76 ** & 89 ** \\ [PERSON] et al. [13] & 87 ** & 88 ** & 89 ** & 96 ** & 94 ** \\ \hline \hline \end{tabular}
\end{table}
Table 5: Mann–Whitney U test for the values obtained compared with [PERSON] et al. [11], [PERSON] et al. [12], and [PERSON] et al. [13]. “**” indicates that there is no significant difference at the 0.05 level (\(p\geq 0.05\)).  
is a useful tool for making decisions about resource management in agricultural practice in Peru. Rice plots acted as a CO\({}_{2}\) sink from 6:00 a.m. to 6:00 p.m. and as a CO\({}_{2}\) source during the remaining period. The minimum NEE values at 82, 89, 102, 111, and 126 DPS were \(-\)9.51, \(-\)9.25, \(-\)13.63, \(-\)12.9, and \(-\)12.5 umolCO2 m\({}^{2}\) s\({}^{-1}\); the maximum NEE values for the same dates were 0.68, 0.36, 0.32, 1, and 0.22 umolCO2 m\({}^{2}\) s\({}^{-1}\), respectively.  
The total seasonal NEE values were \(-\)25.2 and \(-\)34.98 umolCO2 m\({}^{2}\) s\({}^{-1}\) for the growth and reproductive stages, respectively. This represents a difference of 1.4 times between the mentioned stages. On the other hand, NEE was mainly influenced by Rn (R = \(-\)0.75), Tc (R = \(-\)0.69), and RHc (R = 0.66). NEE was negative throughout the rice growth period, demonstrating that the rice field acted as a net CO\({}_{2}\) sink. The results did not show a significant difference compared with previous studies, indicating the optimal performance of the analyzer. Furthermore, differences in CO\({}_{2}\) absorption can primarily be attributed to the type of crop, irrigation management, and climatic and soil conditions. These results are similar to previous studies obtained via chromatographic analysis and eddy covariance (EC), which suggests that the portable analyzer could be an alternative for CO\({}_{2}\) monitoring.  
Conceptualization, L.R.-F.; methodology, M.B.-C. and I.E.-C.; validation, L.R.-F., L.F.d.P. and L.C.-V.; investigation, M.B.-C. and I.E.-C.; resources, L.R.-F., L.C.-V. and L.F.d.P.; data curation, L.R.-F., M.B.-C. and I.E.-C.; writing--original draft preparation, M.B.-C., I.E.-C. and L.R.-F.; writing--review and editing, L.R.-F., L.C.-V. and L.F.d.P.; supervision, L.R.-F., L.C.-V. and L.F.d.P.; project administration, L.R.-F. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Scientific Research and Advanced Studies Program (PROCIENCIA) of PROCIENCIA-Peru, under the project \"Implementation of the technological tool in the development of a precision system with remote sensors to optimize the use of water and reduce the emission of greenhouse gases in rice fields for the benefit of farmers in the Lambayeque region\" (Contract: PE501078113-2022).  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors declare no conflicts of interest.