# Partitioning Evapotranspirationiration in a Cotton Field under
## 4 Discussion
### Causes of Changes in T/ET  
The \(T\) of cotton fields under mulched drip irrigation in an arid region accounted for 61% of the total \(ET\), and its change process was also consistent with the total \(ET\). By comparing the change processes of environmental factors and \(ET\), \(T\), and \(E\), the correlation coefficient between different \(ET\) components and environmental factors is shown in Table 3. It was found that \(T_{air}\) and \(R_{n}\) were the main factors affecting \(T\)/\(ET\). At the seedling stage, the cotton plants were short and the number and area of leaves were small, which was not conducive to \(T\). At this stage, the \(T_{air}\) and \(R_{n}\) was low, but the \(RH\) was large, which was also not conducive to \(E\). Because the canopy coverage of cotton plants was not conducive to \(E\), the \(T_{air}\) and \(R_{n}\) were the main factors affecting \(T\)/\(ET\). \begin{table}
\begin{tabular}{c c c c c c} \hline
**Growth Stage** & **Component** & \(\mathbf{T_{air}}\) & \(RH\) & \(\mathbf{R_{n}}\) & **VPD** \\ \hline \multirow{3}{*}{Seedling stage} & \(T\) & \(0.54\) & \(-0.29\) & \(0.58\) & \(0.21\) \\  & \(E\) & \(0.53\) & \(-0.27\) & \(0.58\) & \(0.21\) \\  & \(ET\) & \(0.53\) & \(-0.28\) & \(0.58\) & \(0.21\) \\ \hline \multirow{3}{*}{Budding stage} & \(T\) & \(0.61\) & \(-0.32\) & \(0.60\) & \(-0.18\) \\  & \(E\) & \(0.63\) & \(-0.32\) & \(0.63\) & \(-0.22\) \\  & \(ET\) & \(0.63\) & \(-0.32\) & \(0.62\) & \(-0.20\) \\ \hline \multirow{3}{*}{Blooming and boll stage} & \(T\) & \(0.63\) & \(-0.45\) & \(0.49\) & \(-0.16\) \\  & \(E\) & \(0.56\) & \(-0.39\) & \(0.43\) & \(-0.19\) \\  & \(ET\) & \(0.62\) & \(-0.44\) & \(0.48\) & \(-0.17\) \\ \hline \multirow{3}{*}{Boll opening stage} & \(T\) & \(0.50\) & \(-0.21\) & \(0.65\) & \(0.54\) \\  & \(E\) & \(0.48\) & \(-0.20\) & \(0.63\) & \(0.53\) \\  & \(ET\) & \(0.49\) & \(-0.21\) & \(0.64\) & \(0.54\) \\ \hline \multirow{3}{*}{The whole stage} & \(T\) & \(0.73\) & \(-0.02\) & \(0.59\) & \(0.27\) \\  & \(E\) & \(0.24\) & \(-0.07\) & \(0.25\) & \(0.18\) \\ \cline{1-1}  & \(ET\) & \(0.71\) & \(-0.08\) & \(0.59\) & \(0.30\) \\ \hline \end{tabular}
\end{table} 
Table 3: Correlation coefficients between different \(ET\) components and environmental factors. Figure 9: Hyperbola fitting of _GPP_ and different environmental factors. on the soil were too low, \(E\) was stronger than \(T\), more than 60% of irrigation water was lost through \(E\). However, both \(T\) and \(E\) were small in absolute terms, and the \(ET\) was weak. When cottons entered the budding stage, the plant began to grow rapidly, and the number and area of leaves increased to promote the enhancement of \(T\). In this stage, \(T_{air}\) and \(R_{n}\) gradually increased, but \(RH\) decreased to promote the enhancement of \(E\). However, the canopy coverage of cottons to the soil increased to inhibit \(E\), so \(T\) was stronger than \(E\) and the \(ET\) was enhanced. When cottons entered the blooming and boll stage, the plants were basically shaped, the leaves grew completely, the number and area of leaves reached the maximum value in the whole stage, and \(T_{air}\) and \(R_{n}\) also reached the maximum value in a year in this stage. However, too high \(T_{air}\) and \(R_{n}\) would inhibit the stomatal conductance of cotton leaves, so \(T\) would decrease when \(T_{air}\) and \(R_{n}\) were at their maximum. This resulted in large fluctuations in \(T\) at this stage, but compared with other stages, \(T\) in this stage was stronger than the other three stages. Although the canopy coverage of cottons to the soil was the largest in the whole stage, which inhibited \(E\) to the greatest extent, \(E\) was also the strongest in this stage due to \(T_{air}\) and \(R_{n}\). Therefore, \(ET\) in the blooming and boll stages was the strongest in the whole stage and dominated by \(T\). However, the \(T\)/\(ET\) of blooming and boll stage was much higher than the results under other similar conditions, which was consistent with the research results of [PERSON] et al. (2015).