We designed two NGSS-aligned middle school classroom experiments to
investigate the effects of biochar on plant growth and soil respiration.
Biochar is a carbon-rich material, produced by heating organic matter
under limited oxygen, that is added to soils to improve fertility, to promote
plant growth, and as one possible strategy to help mitigate climate change.
The experiments offer an ideal case study for students learning
fundamentals of soil and plant interactions. Soils and biochar are
accessible, are connected to global issues such as agriculture and climate
change, and are the focus of ongoing research in soil science. These
classroom experiments promote authentic science because students design
replicated experiments, collect and analyze data, discuss variability in the
data, and interpret their results in the context of recent research.
Key Words: Soil; plants; biochar; experiment; authentic science.
Soils are the foundation of terrestrial ecosystems and produce food
and fiber, filter freshwater, and regulate carbon cycling and therefore global climate (Wall et al., 2012). Demands for increased agricultural productivity, climate change, and impacts of drought
(IPCC, 2014) put soils at the forefront of global environmental
issues and provide unique opportunities for teaching real-world life
science. Soils provide a great opportunity to study fundamental
ecosystem processes in a local context because they are found
everywhere! Most teachers and students have multiple ways to
access soils – in their backyards, parks, local forests, or garden
stores. Studying soils in classrooms is inexpensive, easy, and provides an ideal way to involve students in timely and authentic scientific inquiry.
We designed two classroom experiments focused on the use of
biochar as a soil amendment to improve soil health. The activities
are aligned with the Next Generation Science Standards at the middle
school level but can be adapted to high school classrooms (NGSS Lead
States, 2013). Biochar serves as an ideal case study for students
learning fundamentals of soil and plant interactions because it is easily
accessible, connected to global environmental issues, and is the focus
of ongoing research. Studying biochar also supports students in
engaging in authentic science by discussing data variability and inter-
preting contrasting research results.
Biochar is made by heating organic matter in the absence of
oxygen (Figure 1). Indigenous people of the Amazon have long
incorporated charcoal into soils to increase fertility and productivity in what would otherwise be infertile tropical soils (Figure 2).
In South America, the treated soils are known as Terra Preta de
Indio soils, or Amazonian Dark Earths (Glaser et al., 2001; Figure 2).
Scientists have found that biochar can increase soil moisture (Basso
et al., 2013; Yu et al., 2013) and stimulate the growth and activity of
soil microorganisms (e.g., bacteria and fungi) to enhance nutrient availability to plants (Biederman & Harpole, 2013; Liu et al., 2016). Current investigations focus on how biochar might enhance soil fertility
and improve crop productivity (Lehmann, 2007).
The impacts of biochar amendment depend on the type of
biochar ( i.e., from what and how it was produced) and the soil
type (e.g., texture, organic matter content, nutrient availability,
acidity; Lehmann & Joseph, 2015). These factors explain why
many biochar experiments yield different results. So far, the
greatest effects of biochar have been seen in tropical, arid, and
acidic soils (Jeffery et al., 2011). Research to determine which
types of biochar improve soil moisture and nutrient availability
is still ongoing (Zhang et al., 2016).
Aside from improving soils for plant growth, research suggests
that the production and application of biochar may store carbon in
soils for decades to millennia, reduce the net amount of carbon
released to the atmosphere, and help mitigate rising atmospheric
CO2 concentrations responsible for climate change (Liu et al., 2016;
Figure 3). The pyrolysis process to make biochar requires carbon
and energy inputs. By using a local feedstock for the pyrolysis process
or even using the solid waste product from biofuel production, biochar can sequester more carbon than is used in its production process
(Woolf et al., 2010; Field et al., 2012). Biochar alone is not a sufficient
The American Biology Teacher, Vol. 81, No. 4, pp. 256–268, ISSN 0002-7685, electronic ISSN 1938-4211. © 2019 National Association of Biology Teachers. All rights
reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press’s Reprints and Permissions web page,
www.ucpress.edu/journals.php?p=reprints. DOI: https://doi.org/10.1525/abt.2019.81.4.256.
Teaching Authentic Soil & Plant
Science in Middle School Classrooms
with a Biochar Case Study
• YAMINA PRESSLER, MARY HUNTER-LASZLO,
SARAH BUCKO, BETH A. COVITT, SARAH URBAN,
CHRISTINA BENTON, MICHELLE BARTHOLOMEW,
AMANDA J. MORRISON, ERIKA J. FOSTER,
SYLVIA D. PARKER, M. FRANCESCA COTRUFO,
JOHN C. MOORE