# Growth and Photosynthetic Response of _Capsicum annum_ L. in Biochar Amended Soil
## 3 Results  
### Vegetative and Reproductive Plant Growth  
As an indicator for plant growth stem thickness and plant height were monitored. Stem thickness values were increasing at rates between 0.24 (control) and 0.42 mm d\({}^{-1}\) (BC2.5), representing statistically significant changes between the control and BC2.5 treatments (\(p<0.001\)). Plant height measurements were varying between 1.4 (control) and 2.66 mm d\({}^{-1}\) (BC5.0; Table 2). The plant growth showed an exponential increase in all treatments until week 6, where the growth slowed down reaching a plateau (Figure 2a) at a time when the fruit growth took place. Even though biochar addition showed larger plant height and stem thickness values, the amount of biochar added to the soil showed no linear response, e.g., BC2.5 treatment had the highest average values during plant development at the end of the experiment. Increasing biochar amount resulted in significant differences in plant height between treatments until 2.5% of biochar addition, while stem thickness only showed significant differences between BC2.5 and all other treatments (Table 2). Soil pH can influence the growth of pepper plants, with optimal pH values ranging between 6 and 8. In the present study the soil pH was slightly alkaline for all treatment (average pH of 7.81, 8.06, 8.16, and 8.15 for C, BC0.5, BC2.5, and BC5.0, respectively), indicating similar plant growth effects among treatments. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Treatment**} & \multirow{2}{*}{**Plant Height 1**} & \multicolumn{2}{c}{**Stem Thickness 1**} & \multirow{2}{*}{**Leaf Area**} & \multicolumn{2}{c}{**Aboveground**} & \multicolumn{2}{c}{**Root Dry**} & \multirow{2}{*}{**Fruit Yield**} \\  & & & **Thickness 1** & & & & **Dry Mass** & & & \\ \hline  & **Average** & **SD** & **Average** & **SD** & **Average** & **SD** & **Average** & **SD** & **Average** & **SD** \\ \cline{2-10}  & \multicolumn{2}{c}{**mm**} & \multicolumn{2}{c}{**mm**} & \multicolumn{2}{c}{**mm2**} & \multicolumn{2}{c}{**g**} & \multicolumn{2}{c}{**g**} & \multicolumn{2}{c}{**g**} \\ \hline Control & 262.38a & 27.71 & 7.02a & 0.95 & 25,547a & 5895 & 2.67a & 0.88 & 2.22a & 0.51 & 312.24a & 15.61 \\ BC0.5 & 278.25b & 17.84 & 6.66a & 1.05 & 25,735a & 6102 & 2.59a & 0.64 & 2.56 ab & 0.27 & 393.60a & 19.68 \\ BC2.5 & 304.13c & 33.76 & 7.88b & 0.92 & 32,861b & 5804 & 3.23a & 0.50 & 3.44b & 0.82 & 459.52a & 22.98 \\ BC5.0 & 286.25c & 39.02 & 7.27a & 1.35 & 30,656 ab & 12,840 & 3.21a & 1.47 & 2.95 ab & 0.17 & 392.72a & 19.64 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average plant growth parameter measurements for the control and biochar (BC) amended treatments at the end of the experiment. Statistically significant differences are indicated by different letters. SD is the standard deviation of the data. One-way ANOVA, Tukey post-hoc test, \(n=8\). Figure 2: Plant growth values based on _Capsicum annuum_ L. (**a**) stem thickness and (**b**) plant height collected weekly. \(n=8\) to 14; Mean, \(\pm 5\)D. Statistically significant differences (\(p<0.05\)) are indicated by different letters, while n.s. signifies not significant differences between treatments. Based on the 12 weeks averages, BC2.5 treatments showed 15.44% higher stem thickness compared to control treatment, while BC0.5 and BC5.0 had 3.77 and 3.56% increases, respectively. These changes showed no substantial influence on stem thickness of low or high biochar additions to the silt loam soil. When comparing plant heights during the overall experimental period, BC2.5 and BC5.0 treatments had 13.58 and 12.10% increase, while BC0.5 had only 6.98% increase in height compared to controls. These results show that biochar addition helped plant growth during the growing phase; however, after 6 weeks all plants reached a plateau value and the difference between treatments were kept relatively constant (Figure 2).