## 3 Results and Discussion
### Importance of Input Variables and Processing Methods on WUE Estimates
#### 3.2.1 Importance of Water Use Variable
2.2 Importance of Carbon Input Variables on Differences between Harvest Water Use Efficiency and Ecosystem Water Use Efficiency  
HWUE and EWUE techniques are inconsistent with one another due to the differences in assimilated GPP and accumulated above ground biomass carbon content (BioC) because of carbon allocation and photorespiration. Even with the same water use variable, there are discrepancies in the magnitude of differences measured between crops; alfalfa's HWUEET estimate was 75% lower than its EWUES value, while maize's HWUEET estimate was 33% lower than EWUES (Table 2). This provides inherent inconsistencies in techniques since some crops such as maize produce more biomass per carbon assimilation (i.e., higher carbon use efficiencies) than other crops (c.f. [77]). These differences in carbon use efficiencies are compounded by the carbon allocation issue mentioned earlier, where alfalfa invests significantly more into below ground biomass than maize. \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline  & & **Date** & **P a ** & **Median** & **Median** & **Median** & **BioC e ** & **GPPPs f ** & **Median** \\ \hline Alfalfa & Cut 1 & 21 Apr-7 June & 0.93 & 1.75 & 2.21 & 1.15 & 0.548 & 1.41 & 5.45 & 1.25 & 3.95 \\  & Cut 2 & 8 June–6 July & 0.54 & 1.48 & 3.57 & 2.74 & 1.76 & 0.98 & 4.21 & 2.01 & 5.38 \\  & Cut 3 & 7 July–13 Aug & 0.95 & 1.67 & 3.30 & 2.68 & 1.69 & 1.09 & 5.04 & 1.82 & 4.68 \\  & Cut 4 & 14 Aug–21 Sept & 0.90 & 1.24 & 2.22 & 1.87 & 1.11 & 1.29 & 4.42 & 1.57 & 4.11 \\  & Growing Season & 21 Apr–21 Sept & 3.30 & 6.14 & 2.65 & 1.97 & 1.15 & 4.77 & 19.1 & 1.68 & 4.44 \\ \hline Maize & Growth Stage 1 & 3 May–26 June & 1.22 & 2.05 & 4.20 & 1.93 & 0.990 & 0.51 & 2.58 & 0.712 & 3.42 \\  & Growth Stage 2 & 27 June–18 July & 0.38 & 1.15 & 9.60 & 5.37 & 3.93 & 1.99 & 4.00 & 3.76 & 6.34 \\  & Growth Stage 3 & 19 July–13 Aug & 0.68 & 1.22 & 5.47 & 4.22 & 3.56 & 2.73 & 4.21 & 3.02 & 6.79 \\  & Growth Stage 4 & 14 Aug–11 Sept & 0.89 & 1.07 & 3.46 & 2.54 & 2.12 & 4.24 & 3.44 & 2.17 & 4.59 \\  & Growing Season & 3 May–11 Sept & 3.16 & 5.50 & 4.76 & 3.46 & 2.46 & 9.48 & 14.2 & 1.76 & 5.37 \\ \hline \end{tabular}  
* P = Precipitation; b ETS = Evapotranspiration from EddyPro processing methods; c ETF = Evapotranspiration from Fluxpart processing methods; d TF = transpiration from Fluxpart processing methods; e BioC = Biomass carbon content; f GPPs = Gross primary productivity from EddyPro/REddyPro processing method; f GPPs = Gross primary productivity from Fluxpart processing methods.  
\end{table} 
Table 3: WUE input variables for maize and alfalfa sites for the 2018 growing season. Alfalfa site was divided into subsections of cuts (1–4), while maize was divided into growth stages (early growing season, mid-season accelerating growth, pre-reproductive phase, and reproductive phase). Precipitation (P) and evapotranspiration from EddyPro/REddyProc method (ETS) are presented in \(\times 105\) g H\({}_{2}\)O m\({}^{-2}\), while median half-hourly evapotranspiration by EddyPro/REddyProc (MED ETS) and flux variance similarity (FVS) (ETF), and transpiration by FVS (TF) are presented in \(\times 10^{-2}\) g H\({}_{2}\)O m\({}^{-2}\) s\({}^{-1}\). Biomass carbon content (BioC) and gross primary productivity (GPP) from EddyPro/REddyProc method (GPPS) were presented as \(\times 105\) mg C m\({}^{-2}\) over the stated period, while median GPP by EddyPro/REddyProc (MED GPPS) and FVS (GPP) were presented as \(\times 10^{-1}\) mg C m\({}^{-2}\) s\({}^{-1}\).