## 2 Materials and Methods  
### Turnips Field and Experimental Design  
The study involved 126 field plots arranged in a randomized complete block design with three replicates. Three different turnip varieties and 14 treatments were utilized. Each treatment had dimensions of 3 feet (0.91 m) in width and 4 feet (1.22 m) in length. The field was exploited to cultivate three varieties of turnips: _Brassica rapa_ var. Purple Top White Globe PTWG, var. Scarlet Queen Red SQR, and var. Tokyo Cross TC. The 14 soil treatments were employed in the experiment and included sewage sludge SS, horse manure HM, chicken manure CM, vermicoprost Vermi (worm castings), commercial inorganic fertilizer (NPK 19:19:19), commercial organic fertilizer (Nature Safe NPK 10:28), as well as no-mannure native soil). Additionally, biochar was added to the SS, CM, HM, Vermi, Org, Inorg, and UA treatments. The native soil in the experimental plots was Bluegrass-Maury Silty Loam with a pH of 6.1 and an organic matter content of 2.2%. The soil had 56% silt, 38% clay, and 6% sand, along with other properties listed in Table 1.  
To standardize the nitrogen (N) content across different soil treatments, each soil amendment was mixed with the native soil in the experimental plots at a rate of 5% nitrogen on a dry weight basis at the amounts shown in Table 2. The SS was obtained from the Metropolitan Sewer District in Louisville, KY, USA, while the CM (composed manure) was sourced from the Department of Animal and Food Sciences at the University of Kentucky in Lexington, KY, USA. HM was collected from the Kentucky Horse Park in Lexington, KY, USA, and Vermicompost (Vermi) was obtained from Worm Power in Montpelier, Vermont, USA. Organic and inorganic fertilizers were purchased from Southern States Stores in Lexington, KY, USA. Prior to planting in the experimental plots, each soil amendment was added to the native soil and mixed thoroughly to a depth of 15 cm of the topsoil using a root tiller. Turnip seeds (_Brassica rapa_) were then manually planted in the freshly tilled soil with an 18-inch spacing between rows. Drip irrigation was employed as necessary. In the remaining seven treatments, the soil was mixed with 10% (_w/w_) biochar obtained from Wakefield Agricultural Carbon in Columbia, MO, USA. The biochar used in this study had the following characteristics: total inorganic carbon content of 0.34%, particle size less than 0.5 mm, pH of 7.4, biochar surface area of 366 m\({}^{2}\)/g (dry weight basis), 88%, total organic carbon content, bulk density of 480.6 kg/m\({}^{3}\), and moisture content of 54%. Throughout the growing season, routine agricultural tasks were performed as needed. During the growing season, two insecticides, namely esfenvalerate (sold as Asana XL) and Baythroide XL (containing \(\beta\)-cylthurrin), were applied three times using the recommended application rate [21]. At the time of harvest, three different turnip varieties (PTWG, SQR, and TC) were taken out of the soil. Their shoots and roots were cleaned with tap water and then separated utilizing a sharp knife. The concentrations of GSLs (glucosinolates), vitamin C, total phenols, and soluble sugars in the shoots and roots were determined as explained below.