Advancing Soil Fertility: Biochar and Plant-Growth-Promoting Rhizobacteria as Soil Amendments

EPA Grant Number: FP917246
Title: Advancing Soil Fertility: Biochar and Plant-Growth-Promoting Rhizobacteria as Soil Amendments
Investigators: Hale, Lauren Elizabeth
Institution: University of California - Riverside
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2010 through August 31, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Science & Technology for Sustainability: Green Engineering/Building/Chemistry/Materials


Many studies have displayed the ability of plant-growth-promoting Rhizobacteria (PGPR) to serve as eco-friendly, biological fertilizers when applied to agricultural soils. Furthermore, a soil amendment, biochar, improves a soil’s fertility and nutrient and water-use efficiencies and also has the potential to mitigate climate change by sequestering carbon into soils. The objective of this research is to develop a treatment of biochar inoculated with a bio-fertilizer that will optimize the positive benefits associated with PGPR.

The goal of this project is to optimize a combination of biological fertilizers and a soil amendment, biochar, to improve soil fertility of arid-zone soils. The extent to which bacteria produce enzymes that interfere with plant-stunting hormones and the ability of these microorganisms to thrive in the pores of biochar particles will be measured using quantitative PCR and fluorescent, transgenic bacteria. This system provides an eco-friendly soil treatment useful for sustainable agriculture.


This study is centered on the ability of PGPR to produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase, an enzyme that degrades a precursor of plant hormone ethylene. Ethylene is produced by plants in response to drought or high salinity and causes stunted root growth, reducing crop yields drastically. The first phase of this study will employ quantitative PCR to enumerate ACC deaminase genes across soil bacterial populations in the rhizospheres of cowpea plants treated with combinations of bio-fertilizer and biochar. DNA will be isolated from zones soil directly affected by plant roots, the rhizosphere, in weekly intervals throughout a drought-simulated root-box experiment. The abundance of ACC deaminase genes in this DNA will be correlated with plant growth patterns, treatment type, and time. The second phase of this experiment will examine the expression of ACC deaminase genes by a bacteria modified to display bioluminescence when ACC deaminase is expressed. This will allow for the detection of gene expression in relation to location and time and will display the overall survival of the soil inoculates.

Expected Results:

From the first phase of this study it should become apparent that there is a combination of biofertilzer and biochar treatments that maximize the ability of cowpea plants to thrive under stress from drought. Furthermore, the gene copy number of ACC deaminase necessary to influence cowpea survival can be quantified. Once this treatment is determined the second phase of this experiment should produce more evidence supporting the ability of these combined soil amendments to improve bacterial enzymatic promotion of plant growth. The observation of bioluminescence will give insight as to when and where microbial expression of ACC deaminase is the most influential. Furthermore, bacteria inoculated directly into soils often are not competitive with native microorganisms and their populations quickly diminish. It is expected that biochar will provide soil inoculants with pre-associated niches, increasing their survival in soil and attributing biological fertilizers with longer lasting benefits.

Potential to Further Environmental/Human Health Protection
This research can be directly applied to arid-zone agriculture to combat the effects of desertification by rejuvenating soils and increasing their water and nutrient use efficiencies. Improved soil health lessens the need for chemical fertilizer applications which can help prevent disastrous environmental problems associated with eutrophication. Furthermore, insight into the potential of biochar to function as an inoculums medium can promote its production from biological wastes, preventing these materials from emitting large amounts of carbon dioxide into the atmosphere by being burned, composted, or stored in landfills.

Supplemental Keywords:

biochar, biological fertilizers, PGPR, ACC deaminase, land use efficiency, biological-waste management, sustainable agriculture, mitigation of climate change,

Progress and Final Reports:

  • 2011
  • 2012
  • Final