# Growth and Photosynthetic Response of _Capsicum annum_ L. in Biochar Amended Soil
## 4 Discussion  
Biochar addition can result in increased plant biomass, especially in leaves [39]; however, the amount of biochar added to the soil also influence biomass production rates. [PERSON] et al. [39] found that up to 60 g biochar per kg soil could increase the biomass production by 39%, while 90 g biochar per kg soil showed similar biomass production as the control treatments. This finding is similar to the present study's finding, as BC5.0 showed a somewhat less amount of biomass compared to BC2.5 treatment by the end of the experiment. However in the present experiment the high biochar addition did not decrease biomass production, instead still substantial differences were observed compared to control at specific sampling times (Figure 3). The findings of biochar effects on plant growth and fruit production emphasize the necessity for optimization to local parameters prior to biochar addition to soils. Currently there are many studies without consistent data on the effectiveness of biochar amended soils to crop and fruit yield. [PERSON] et al. [40] found no significant effects of biochar on canopy growth of spring wheat, nor yield components. Similarly, [PERSON] et al. [18] observed no distinct effect of biochar on rice grain yield. On the other hand, [PERSON] et al. [41] noted significantly higher plant height, leaf area index, and grain yield for maize grown in biochar amended soils. Fluctuations in PRI can be used as an indicator of changes in photosynthetic dynamics and gross primary production (GPP) [37]. PRI can be used as a proxy of light use efficiency (LUE), also can be used to complement normalized difference vegetation index (NDVI) to estimate GPP [42; 43]. The midday average PRI values were consistently higher for the control compared to BC2.5 and BC5.0 treatments in the present study, which could indicate LUE changes as influenced by biochar addition. The midday PRI values tend to be more sensitive to water stress than earlier in the morning or later afternoon measurements [44], thus better providing values of changes in PRI. Our measurements were chosen in this time frame, expecting the largest differences between treatments. Strong relationship between PAR and PRI values can be observed for water stressed plants [27]. However, in the present study, increasing PAR did not change significantly the PRI values, although longer drought conditions were disabled by watering the plants. The results of the relationships between these parameters highly depend on the research environment, different types of plants or experimental setup, such as laboratory or field-scale study might result different outcomes. Strong relationship was observed between PRI and PAR values by [PERSON] et al. [45], while investigating different tree canopies. Our results were comparable at higher PAR values (\(>\)400 \(\mathrm{\SIUnitSymbolMicro m^{-2}~{}s^{-1}}\)), where a plateau in the values was occurring. In general, at all PAR ranges the PRI were highest for the control treatment, indicating potentially higher sensitivity for water or other environmentally related stress for the control plants. Biochar amendment to improve the water holding capacities of a given soil, especially for sandy soils, have been widely investigated during the last few decades [46; 47]. Several studies observed that biochar amendment can substantially affect soil moisture levels [26; 48], which can be available for plants to grow. However, no significant effects on soil moisture were noted in many studies depending on the type and/or amount of biochar added to the soils [49; 50]. In the present experiment natural rainfall was adjusted with watering when it seemed necessary to minimize drought stress to the pepper plants; nevertheless, the pot setup could increase evaporation concurrent with fasten soil temperature changes as a response to air temperature fluctuations. The present study disabled longer time periods where the plants could be investigated for either drought or flooded conditions.