Recipient Organization
VIRGINIA POLYTECHNIC INSTITUTE
(N/A)
BLACKSBURG,VA 24061
Performing Department
Biological Sciences
Non Technical Summary
Biochar has attracted the interest of farmers in recent years but enthusiasm for its putative benefits as a soil amendment has outpaced scientific understanding of how and under what climate, soil, and management circumstances its benefits can best be achieved. The objective of our proposed research is to evaluate methods for producing and activating biochar as a soil amendment for improving soil health in diverse managed ecosystems. Our research addresses the priorities of the USDA Bioenergy, Natural Resources, and Environment Program by examining the efficacy of a natural bio-based product in promoting agroecosystem sustainability and the essential ecosystem services that soils provide. Biochar applications improve soil health in a variety of ecosystems, primarily through modifying soil microstructure in ways that enhance aggregation and hydraulic properties. We hypothesize that these changes in soil microstructure promote soil health by increasing carbon sequestration in aggregates and retention of water, and nutrients among soil microsites. Using a combination of field experiments, advanced imaging techniques, and modeling we will examine the mechanisms by which biochar influences soil structural and hydraulic properties, and thereby the mobility of nutrients, carbon sequestration, and microbial communities in controlled field studies across a range of managed agricultural systems (pasture, row-crop, forest) and soil types (fine and coarse texture soils across 6 orders). This research will include new and existing biochar experiments to encompass a range of temporal perspectives on the benefits of biochar to growers and the long-term implications for how biochar potentially influences multiple indicators of soil health.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
0%
Goals / Objectives
Our objective is to evaluate methods for producing and activating biochar as a soil amendment for improving soil health, carbon sequestration, and productivity in diverse managed ecosystems. Soil health is the sustained capacity of soil to function as a vital living ecosystem to support plants, animals, and humans. The USDA Natural Resources Conservation Service recommends several crucial indicators to evaluate soil health including: soil carbon content and mineralization potential, soil structural stability, bioavailable nitrogen, and microbial activity and diversity. Biochar applications have been demonstrated to enhance all of these indicators in a variety of soil ecosystems, primarily through modification of the soil microstructure in ways that enhance soil aggregation and hydraulic properties. We hypothesize that these changes in soil microstructure promote soil health by increasing carbon sequestration in soil aggregates and connectivity of microbial communities among soil microsites. Here we propose a project seeking to use new and existing biochar experiments in agricultural ecosystems in Virginia and forest ecosystems in Minnesota to examine the interactive effects of biochar and soil composition on multiple metrics of soil health, including: soil carbon content and mineralization, soil micro-structural and aggregation, bioavailable nitrogen, and microbial activity and diversity.
Project Methods
Biochar will be sourced from a commercial producer, made from softwood, and will be created by either a pyrolysis or gasificationtechnology. The temperature of the process will be controlled to produce chars on either side of the "sweet spot" of 500-550ºC to generate biochar from the same feedstocks with different characteristics, most importantly to our objectives: bulk density, surface area, and carbon content. The chars will be analyzed to IBI standards and be sized and sifted to produce our target particle distribution of 90% less than 1mm.A no-activation control, a compost tea, and a bloodmeal treatment will be used to distinguish biotic effects from nutrient effects associated with activation. The purpose of the activation step is to "charge" the biochar with essential plant nutrients (N, P, K) in a consistent manner across all of the participating farms. This step is intended to standardize typical methods of biochar activation used by many growers, soaking the biochar in a compost tea or mixing with compost typically. Compost will be analyzed for NPK content to normalize with bloodmeal additions. Common biochar activation slurries will be prepared from locally sourced farm compost combined with biochar prepared from wood biomass, i.e., compost teas. Compost teas will be prepared by soaking local farm compost in cattle tanks. Prior to soil application biochar will be mixed with compost or bloodmeal in a stock tank or suitable container large enough to hold the activated biochar. Biochar treatment combinations will be weighed into 62.5 kg dry weight equivalent aliquots and applied evenly to pre-cut, pre-surveyed, and marked 25 m2 plots using a fertilizer spreader. Following application biochar will be tilled into the soil to a depth of 10 cm.Soil samples will be collected in 5 cm increments from the top 10 cm of soil and sieved to <2mm fine-earth fraction. To address our research objectives, we will use the soil health indicators and associated laboratory methods recommended by the USDA NRCS. To examine the effects of different biochar types on soil structurewe will measure bulk structural properties of soils collected from the existing experiments and newly established experiment using standard intact core methods to estimate bulk density and porosity. We will use wet-sieving procedure to separate particulate organic matter fractions to characterize soil aggregation (macro, micro, and mineral-associated and their associated carbon content. Additionally, we will conduct particle size analysis of soils to characterize the length-scale heterogeneity of treated and untreated soils using the standard hydrometer method and laser light scattering measurements.We will characterize the effects of different biochar types on soil microstructure using experimental imaging techniques. Soil samples will be scanned and imaged using X-ray micro-CT, which will provide 3D pore geometry data for pore-scale lattice Boltzmann simulations of the pore flow fields and solute transport in the pore space. Co-PI Chen is a part-time faculty researcher associated with U.S. DOE's National Energy Technology Laboratory (NETL), and has access to NETL's various X-ray CT scanners, including a Zeiss micro-CT scanner that can achieve a spatial resolution of 1 micron per pixel length. In this proposed project, X-ray CT and FIB-SEM scanning will be used to characterize the geometrical and mineralogical modifications on sediment grain surfaces due to biochar amendment. Digital-image-based lattice Boltzmann simulations will be used to quantify the complex, coupled interactions between pore geometry change, surface wettability, and fluid flow and mass transport in the pore space.We will use results from the imaging analyses to model hydraulic properties of soil and soil-biochar matrices. Microscopic imaging can be combined with direct numerical simulation to understand how fluid flow occurs within soil microstructure. Simulation provides a first-principles approach to study how biochar application influences water retention properties in soil. Within the vadose zone, the particular configuration of water and air in the soil microstructure determines the availability of nutrients and necessarily influences microbial colonization. Lattice Boltzmann methods are a mature class of numerical methods that are well-suited to simulation of water-gas flow through soils.We will characterize the effects of different biochar types on soil carbon cycling and sequestration using standard automated elemental analysis and soil respiration approaches. Three g of air-dried soil will be ground in a ball mill and run for total C and total N on an Elementar Vario MAX cube (Elementar Americas Inc., Mt. Laurel, NJ, United States) in the Virginia Tech Ecosystem Analyses Laboratory. To estimate labile soil organic carbon in soils exposed to out biochar treatments we will conduct a laboratory incubation procedure to measure CO2 evolution from soil microcosms held at 65% of field capacity water content and 20°C at five time points over 28 days. Pre- and post-incubation extractions will be used to characterize potential net nitrogen and phosphorus mineralization as an index of plant available nutrients. Soil extracts will be analyzed for dissolved organic C (DOC), inorganic N, and soil P. For DOC, a 10g (dry equivalent) sample will be shaken for 1 hour in 50mL 0.5M K2SO4, and gravity filtered through #42 Whatman filters and run on a Vario MAX CUBE TOC analyzer. For inorganic N, a 10g (dry equivalent) sample will be shaken for 1 hour with 50mL KCl, then gravity filtered through #42 Whatman filters before being run on a Lachat FIA. For soil P, 2g (dry equivalent) samples will be extracted and analyzed for soil P using the Mehlich 3 method (Mehlich 1984). The Mehlich 3 extraction method was chosen for P because it is widely used to determine nutrient content of agricultural soils and is the best option across a range of soil pH.We will characterize the effects of different biochar types on soil microbial communities using standard qPCR and amplicon sequencing approaches. We will extract DNA from ~0.25 g of fresh soil using DNeasy PowerSoil kits (Qiagen, Valencia, CA, USA) and quantify yield using a Qubit fluorometer (Thermo Fisher Inc., Waltham, MA, USA). Total abundance of bacteria and fungi will be estimated via qPCR amplification of the 16s rRNA gene and the internal transcriber spacer (ITS) region, respectively. Each qPCR reaction will consist of 10 µl Quantitect SYBR green master mix (Qiagen, Valencia, CA, USA), 0.5 µm forward and reverse primer, 3 ng DNA template, and nuclease-free H2O, brought to 20 µl. For both 16s and ITS, thermal cycling conditions will be set at the following: 15 min at 95°C followed by 40 cycles of 15 s at 94°C, 30 s at 55°C and 30 s at 72°C. Standard curves will be generated by amplifying serial dilutions of plasmids containing cloned copies of the target sequences. All qPCR reactions will be performed in triplicate. Sequencing of 16S amplicons will be performed on the Illumina MiSeq platform at the Virginia Tech Biocomplexity Institute to characterize bacterial community composition in biochar-treated and control soils.Standard bioinformatic pipelines and multivariate statistical techniques will be used to process, analyze, and visualize bacterial amplicon sequence variants. Experimental soil data will be visualized and analyzed using fundamental descriptive statistics, ordination, and linear mixed models to test for significant differences among treatments; post-hoc means comparisons will be used to test for differences between treatments and controls.