## 3 Results and Discussion
Figure 3: Concentrations of glucosinolates in roots, shoots, and whole plant of three varieties of turnips, _Brussica rap_q Tokyo Cross (TC), Scarlet Queen Red SQR), and Purple Top White Globe (PTWG) grown under field conditions, regardless of soil amendment type. Statistical analysis was conducted among three varieties using [PERSON]’s multiple range test in SAS [26]. Values with different letters reveal statistical differences at \(p\leq 0.05\). Soil quality and composition of plants depend on soil biology, where microorganisms via organic matter decomposition, nutrient cycling, and enzymatic activity play an important role in soil fertility and plant composition. The impact of biochar on the activity of soil enzymes was reported by [PERSON] et al. (2020) [PERSON] et al. (2020). During the preparation of biochar, the thermal preparation pyrolysis process increases heavy metals concentration in biochar. Heavy metals impact soil microorganisms and their secreting enzymes. For example, Zn inhibits soil urease activity [PERSON] et al. (2020) and lowers the concentrations of GSLs observed in plants with higher foliar Cd concentrations, whereas Ni in plants induced GSLs at elevated levels [PERSON] et al. (2020). In contrast, several studies did not support biochar's impact on soil productivity and nutritional crop composition. Investigators reported controversy in their findings, with biochar having positive, negative, or insignificant effects on soil microbial communities depending on the biochar source and soil types [PERSON] et al. (2020); [PERSON] et al. (2020); [PERSON] et al. (2020). Table 1 listed the activity of urease, invertase, acid, and alkaline phosphatase in each of the animal manures used in growing turnips, arugula, and mustard plants. Soil enzymes as bioindicators of soil health had been investigated [PERSON] et al. (2020); [PERSON] et al. (2020). [PERSON] et al. (2020) reported no increase in soil alkaline phosphatase activity with biochar addition to CM. Biochar added to native soil reduced the activity of soil alkaline phosphatase by 41% more than the control treatment. Trace metal contamination removes some microorganisms and multiplies others, resulting in changes in soil quality and functionality. For example, alkaline phosphatase activity is significantly inhibited with Cd [PERSON] et al. (2020). Similarly, the breakdown of GSLs into ITC and glucose is dependent on the activity of thioglucosidase. As described earlier, using _Brassica_ crops as green manures reduces soilborne pests and pathogens such as _Rhizoctonia solani_, and _Sclerotinia scleroorum_, the two most damaging soilborne pathogens [PERSON] et al. (2020). Brassica plants are well adapted in Kentucky and other states and hence can be used for pest control either by spreading dried Brassica plant powder or using green manure by incorporating plants into the soil to release ITCs upon hydrolysis of their CSLs content. The process of releasing ITCs from GSL molecules could be improved by (1) selecting high-ITC-content _Brassica_ varieties (i.e., turnip variety TC), (2) releasing more GSLs by increasing plant tissue cellular disruption, and (3) maintaining good soil moisture to facilitate the breakdown of GSLs and release ITCs breakdown products. Concentrations of soluble sugars (3894 \(\upmu\)g g\({}^{-1}\) fresh turnip tissue) and total phenols (610 \(\upmu\)g g\({}^{-1}\) fresh turnip tissue) were greater in variety TC compared to varieties SQR and PTWG, whereas no significant differences in vitamin C content were found among the three varieties (Figure 6). Figure 6: Concentrations of soluble sugars, AA (vitamin C), and total phenols in three commercial varieties of turnip, _Brassica rapa_ Tokyo Cross (TC), Scarlet Queen Red SQR), and Purple Top White Globe (PTWG), irrespective of treatments. Statistical analysis was performed among turnip varieties via [PERSON]’s multiple range test in SAS Antonious et al. (2020). Values with the same letter(s) indicate significant differences (\(p\geq 0.05\)).