# Using an Uptake Enhancer to Mitigate Nitrogen Leaching While Enhancing Uptake Efficiency
## 3 Results
### Effect of Uptake Enhancer Application on N Distribution
#### 3.1.2 Effect of Uptake Enhancer Application on N Distribution Patterns  
The effect of uptake enhancer application on N distribution patterns at all four growth stages is presented in Figure 1a-d. The first sampling time (week 4) in Figure 1a, showed a high N level, which subsequently declined over time, as seen by the declining trend from the first to the fourth sampling time. Treatments with the uptake enhancer (FA and CFA) exhibited the highest N content in the upper soil layers and the lowest in the deeper soil layers for all four sampling periods. Conversely, the N concentration increased with a soil depth in treatments that had no uptake enhancer (F and CF).  
\begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline \multicolumn{2}{l}{**Sampling Time 4 (16 Weeks)**} & & & & & & \\ \hline
**Treatments** & & & & & & & \\ \hline
**Depth (cm)** & **CNTRL** & **C** & **F** & **CF** & **FA** & **CFA** & **\(p\)-Value** \\ \hline
0-10 & 0.008 \({}^{\text{a}}\) & 0.007 \({}^{\text{a}}\) & 0.006 \({}^{\text{a}}\) & 0.008 \({}^{\text{a}}\) & 0.014 \({}^{\text{b}}\) & 0.013 \({}^{\text{b}}\) & **<0.001** \\  & (\(\pm\)0.0081) & (\(\pm\)0.0018) & (\(\pm\)0.0032) & (\(\pm\)0.0014) & (\(\pm\)0.0025) & (\(\pm\)0.0013) & **<0.001** \\ \hline
10-20 & 0.010 \({}^{\text{bc}}\) & 0.007 \({}^{\text{ab}}\) & 0.004 \({}^{\text{a}}\) & 0.010 \({}^{\text{bc}}\) & 0.010 \({}^{\text{bc}}\) & 0.012 \({}^{\text{c}}\) & **<0.001** \\  & (\(\pm\)0.0008) & (\(\pm\)0.0021) & (\(\pm\)0.0009) & (\(\pm\)0.0020) & (\(\pm\)0.0015) & (\(\pm\)0.0016) & **<0.001** \\ \hline
20-30 & 0.010 \({}^{\text{a}}\) & 0.007 \({}^{\text{a}}\) & 0.018 \({}^{\text{b}}\) & 0.011 \({}^{\text{a}}\) & 0.008 \({}^{\text{a}}\) & 0.010 \({}^{\text{a}}\) & **<0.001** \\  & (\(\pm\)0.0053) & (\(\pm\)0.0018) & (\(\pm\)0.0017) & (\(\pm\)0.0006) & (\(\pm\)0.0019) & (\(\pm\)0.0012) & **<0.001** \\ \hline
30-40 & 0.009 \({}^{\text{ab}}\) & 0.012 \({}^{\text{b}}\) & 0.028 \({}^{\text{c}}\) & 0.013 \({}^{\text{b}}\) & 0.002 \({}^{\text{a}}\) & 0.009 \({}^{\text{ab}}\) & **<0.001** \\  & (\(\pm\)0.0063) & (\(\pm\)0.0024) & (\(\pm\)0.0040) & (\(\pm\)0.0014) & (\(\pm\)0.0008) & (\(\pm\)0.0013) & **<0.001** \\ \hline
40-50 & 0.012 \({}^{\text{ab}}\) & 0.015 \({}^{\text{b}}\) & 0.033 \({}^{\text{c}}\) & 0.014 \({}^{\text{b}}\) & 0.003 \({}^{\text{a}}\) & 0.007 \({}^{\text{ab}}\) & **<0.000** \\  & (\(\pm\)0.0060) & (\(\pm\)0.0026) & (\(\pm\)0.0072) & (\(\pm\)0.0017) & (\(\pm\)0.0027) & (\(\pm\)0.0009) & **<0.001** \\ \hline \hline \end{tabular}
\end{table}
Table 2: _Cont._  
Figure 1: Nitrogen content distribution through the soil profile in different treatments, CNTRL: control; C: crop only; F: fertilizer only, CF: crop with fertilizer; FA: fertilizer and uptake enhancer; and CFA: crop with fertilizer and uptake enhancer, across 4 different sampling times: (**a**) week 4, (**b**) week 8, (**c**) week 12, and (**d**) week 16.  
In week 4, the CFA treatment showed the highest N content (0.053%) in the upper soil layer, 3-fold more compared to the N content in the deeper soil layer (0.017%), indicating an effective start in N uptake (Figure 1a). Conversely, the F treatment showed minimal retention in the upper soil layer. By week 8, the CFA treatment maintained stable N content in the upper soil layer, whereas other treatments began to show increased N leaching with soil depth (Figure 1b). By week 16, at harvest, the CFA treatment maintained N levels in the upper soil layer (Figure 1d). Conversely, the F treatment displayed extensive N leaching beyond the 10-20 cm soil depth, and the CNTRL and C treatments exhibited poor N retention, with N freely flowing through the soil profile. At 40-50 cm, the CFA and CF treatments had the lowest N content indicating almost no leaching to these deeper soil layers. Conversely, the F treatment showed the highest N content at the deeper soil layers, indicating that extensive N leaching took place.