Biochar Affects Essential Elements of Carrot Taproots and Lettuce Leaves
Essential element concentrations in crops can affect human health. While biochar has the potential as a soil amendment to improve crop yields, it may also affect the concentrations of elements such as K, Ca, Mg, Fe, Mn and Zn in edible portions of crops. To better characterize effects of biochar on important human nutrients in food crops, we evaluated the effects of biochar on lettuce (Lactuca sativa L. cv. Black-Seeded Simpson) leaves and carrot [Daucus carota subsp. sativus (Hoffm.) Schübl. cv. Tendersweet] taproot elements. Plants were grown in a greenhouse using sandy loam (Coxville, Fine, kaolinitic, thermic Typic Paleaquults) and loamy sand (Norfolk, fine-loamy, kaolinitic, thermic Typic Kandiudults,) series soils, amended with biochar produced from four feedstocks: pine chips (PC), poultry litter (PL), swine solids (SS), switchgrass (SG); and two blends of PC plus PL (PC/PL, 50/50% and 80/20% w/w). Biochar was produced at 350, 500 and 700˚C from each feedstock. Lettuce leaf and carrot taproot total elemental concentrations were determined by inductively coupled plasma analysis. Biochar (especially manure-based) decreased nutrient concentrations in lettuce leaves, with Ca, Mg and Zn affected most. Carrot taproot nutrient concentrations also deceased, but to a lesser extent. Some biochars increased leaf or taproot elemental concentrations, especially K. This study indicated that biochar can both decrease and increase leaf and taproot nutrient concentrations important for human health. Thus, the biochar characteristics should be carefully considered when used as a soil amendment on vegetable crops.