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.

Impact/Purpose

Biochar is a carbon-rich material produced by combustion with reduced or no oxygen of a variety of organic waste materials such as manure, wood chips and straw. Recently there has been considerable interest in biochar as a soil amendment to improve soil health, resulting in increased crop yields. However, the biochar raw material (feedstock) may have chemical and physical characteristics that affect the quality of crops- which is essential for their value as healthy sources of food. For example, biochar can affect the concentration of essential minerals for humans such as K, Ca, Mg, Mn, Fe and Zn. To better understand effects of biochar on these important nutrients in food crops, we evaluated the effects concentrations of these minerals in lettuce leaves and carrot taproots. Plants were grown in a greenhouse using two South Carolina coastal soils with naturally low nutrient concentrations, 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 (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, especially K, increased leaf or taproot elemental concentrations. This study indicated that biochar can both decrease and increase leaf and taproot nutrient concentrations important potentially adversely or beneficially affecting human health. Thus, the biochar characteristics which impact essential element concentrations in plants should be carefully considered when used as a soil amendment on vegetable crops.

Citation

Olszyk, David M, T. Shiroyama, J. Novak, K. Cantrell, G. Sigua, D. Watts, AND Mark G Johnson. Biochar Affects Essential Elements of Carrot Taproots and Lettuce Leaves. American Society for Horticultural Science, 55(2):261-271, (2020). [DOI: 10.21273/HORTSCI14421-19]

DOI: Biochar Affects Essential Elements of Carrot Taproots and Lettuce Leaves