Jack Imel, University of Alaska Southeast undergraduate student, co-authored this article.
Two graduate students from Tennessee State University (TSU) recently utilized resources from the U.S. National Science Foundation (NSF) ACCESS program and presented their work at the 47th annual Tennessee State University symposium. Under the direction of TSU Assistant Professor of Microbiology Joshua OHair and TSU Ecology Professor Dafeng Hui, the TSU students – Funmilayo Akintunde and Navneet Kaur – used the Jetstream2 supercomputer at Indiana University to study the effects of biochar and nitrogen on soil microbial communities.
Biochar, known throughout the agriculture community as an asset in combating soil degradation and improving fertility, is a charcoal-like substance produced by burning organic matter in an environment low in oxygen, or free of it completely. This process – called pyrolysis – consists of loading wood, crop residue, or other organic matter into a specialized oven that heats to a temperature of 350-700 degrees Celsius (662-1,292 degrees Fahrenheit) while restricting oxygen exposure. Adding the resulting product to soil can enhance nutrient retention, benefit soil structure, increase soil water-holding capacity, and help balance soil pH.
Both Akintunde and Kaur used ACCESS allocations on Jetstream2 to better understand how biochar works. Specifically, Akintunde’s study targeted switchgrass, a hardy North American perennial that has been recognized as a promising source of biofuel by the U.S. Department of Energy. “We set up test plots with varying amounts of biochar and nitrogen fertilizer and measured the activity of soil microbes, the identity of those microbes, and the quantity of nitrous oxide gas released from the soil,” Akintunde said. “We found that higher amounts of biochar and lower amounts of nitrogen fertilizer increased microbial biomass.”
Akintunde explained that soil microbes are key to soil health and productivity – they release nutrients into soil through decomposition, nitrogen fixation and phosphorus solubilization. While nitrogen fertilizer alone has been shown to promote the growth of nitrogen-fixing bacteria, overreliance on nitrogen fertilizer poses several problems. Producing nitrogen fertilizer is energy-intensive, and when nitrogen fertilizer is applied to crops, only 40-50% of it is utilized by the plants.
“Unfortunately, 50-60% of the nitrogen fertilizer that farmers have to buy has no tangible benefit to their enterprise,” Akintunde said. “This hefty remainder escapes the soil through volatilization [entering the atmosphere as nitrogen gasses like ammonia], denitrification [converting into nitrous oxide], leaching [diffusing into groundwater] and runoff [being carried away by surface water].”
Akintunde’s findings show that biochar use could be a viable way to supplement the benefits of nitrogen fertilizer while reducing farmers’ reliance on it, thus decreasing the potential reach of its undesirable side effects. Not to mention that biochar use could result in cost savings for farmers. The findings also have a more specific use as a method for switchgrass cultivation. In addition to its use as a biofuel feedstock, switchgrass can be used for grazing livestock, animal bedding, wildlife habitat (particularly for ground-nesting birds) and even soil stabilization and erosion control.
“We were really pleased with the results from this study,” OHair said. “Without access to the power of Jetstream2, we would not have been able to run our calculations to better understand the potential use of biochar, and we are grateful to the NSF for allocations on this valuable resource.”
OHair said that Kaur’s study had a broader focus: the impacts of varying amounts of nitrogen fertilizer, biochar and precipitation on farmland soils in general. He said that ACCESS allocations used on Jetstream2 were helpful in the efforts to examine affected nitrous oxide (N₂O) emissions from soil.
“For this study, we used three methods: mega-analysis [an analysis of multiple meta-analyses], DNA extraction and sequencing, and computer modeling,” Kaur said. “The computer model used — DNDC — was tuned by data from a three-year cornfield experiment conducted at Tennessee State Agricultural Research and Education Center, with the modeling resulting in a real bearing on one of our country’s staple crops.”
Kaur said that the mega-analysis of past studies revealed that biochar use reduced nitrous oxide release by an average of 38.3%. For context, if applied to all U.S. cropland, this reduction would be equivalent to eliminating nitrous oxide emissions from about 125 million acres (50.6 million hectares) of conventional farmland, an area larger than the state of California. The analysis also determined the specific characteristics of biochar (such as being made from grass or wood) that resulted in greater reductions in nitrous oxide emissions.
“Kaur worked hard to explain how the DNA extraction and sequencing showed that applying nitrogen fertilizers significantly altered the microbial makeup of the soil,” Hui said. “Additionally, we found that this effect varied between soils from different ecosystems, which suggests a rich area for future research — if the effects of specific ecosystem parameters on microbial response to nitrogen fertilizer could be determined, then its use could be fine-tuned to elicit the most favorable microbial response.”
You can find Akintunde’s study here and Kaur’s study here.
Resource Provider Institution(s): Indiana University (IU)
Resources Used: Jetstream2
Affiliations: Tennessee State University
Funding Agency: The research was funded by NSF (grant no. 2000058).
Grant or Allocation Number(s): ACCESS:BIO210183; NSF:2000058
The science story featured here was enabled by the U.S. National Science Foundation’s ACCESS program, which is supported by National Science Foundation grants #2138259, #2138286, #2138307, #2137603, and #2138296.