# Growth and Photosynthetic Response of _Capsicum annum_ L. in Biochar Amended Soil
## 1 Introduction  
Biochar is used as soil organic amendment to restore soil health and increase crop yield, especially at areas with degraded soils [1]. Many studies reported on using biochar amendment in soils to improve soil water holding capacity, which can directly cause increase in plant health and productivity [2; 3]. Biochar amendment reported to be enhancing root growth, consequently increasing water retention of soils [4]. Even though biochar use in agricultural settings can influence the soil's biogeochemical properties with or without fertilizer addition [5], its particles can also retain soil nitrogen and supply phosphorous to the plants [6]. As biochar is made of organic materials, in many cases its particles might contain larger amounts of additional nutrients, which can be released into the soil through increased cation retention [7] that can be available for plants to use. However, nutrients from biochar might not be immediately available to plants, as nutrient availability in biochar depends on the environmental parameters and soil type [8]. While potassium (K) availability in biochar is typically high [9], most ofthe nitrogen is present as heterocyclic nitrogen in biochar, which also partially available for plants [8]. Therefore, biochar amendments might be used to lower the amount of synthetic fertilizer [10]. Several studies investigated the effects of biochar on plant growth, biomass production, and crop or fruit yield [11], including _Capsicum annuum_ L. (pepper plants) [12; 13; 14]. Even though many studies demonstrated increases in biomass and yield production as a result of biochar addition to soils [15], negative secondary effects could be observed, such as reduced plant defense against insects or pathogens [16]. Furthermore, several reports noted no significant changes in crop yield, or fruit production, depending on the types and dose of applied biochar [17; 18; 19; 20]. Based on these effects, prior to field application, the intended biochar should be investigated to determine the economically most feasible amount and type to be used. Remote sensing measurements for determining vegetation indices as a nondestructive technique can be very useful in plant studies. Very good correlations between destructive and nondestructive methods could result in the decrease of destructive techniques and increase in remote sensing for gathering data fast with large investigated area. [PERSON] et al. [21] investigated different techniques to measure leaf area index (LAI) including a destructive method and two instruments representing nondestructive techniques. The authors found that the instruments provided similar results to the destructive method with 75% or more accuracy. Therefore plant canopy studies should be primarily applying nondestructive techniques if possible. Measurements of vegetation reflectance can be used to analyze plant response to changes in environmental conditions such as irrigation [22]. LAI and photosynthetically active radiation (PAR) are parameters characterizing plant canopies and its changes [23]. Biochar can result changes in the leaf area of a plant, or of the canopy expressed in leaf area index, which can be an indicator for changes in overall biomass production and possible crop yield. There is a strong relationship between LAI and fraction of absorbed PAR (fAPAR) [24], and both LAI and fAPAR can be used to investigate canopy processes [25]. Normally, there is an optimal dose of biochar or biochar plus fertilizer that need to be added to the soil to result in the highest plant growth and crop/grain yield. However, when outside of this optimal range, such as very high biochar dose present in the soils, reduced canopy and LAI might be observed [18]. Biochar addition can have significant effects on crop photosynthetic activities [26] especially coupling with other environmental parameters such as water availability.