Newswise — An ancient soil amendment — biochar — may be a promising tool for future improvement and maintenance of soil health, according to a study by the Texas A&M Department of Horticultural Sciences.
Amit Dhingra, Ph.D., department chair at Texas A&M College of Agriculture and Life Sciences, Bryan-College Station, led the study, “Metatranscriptomic Analysis of Tomato Rhizospheres Reveals Insights into the Molecular Response of the Plant Microbiome to Organic, Amended with soil biochar”, published in Frontiers in Analytical Sciences. The research showed that biochar improved the soil microbiome and the interactions of plant roots with a spectrum of beneficial microorganisms found there.
“It’s very suitable for horticulture here in Texas because we have 1,300 soil types,” Dhingra said. “This is a proof of principle showing that biochar can be a valuable amendment when it comes to improving and managing soil health.”
The Role of Biochar in Improving Soil Health
Variations of biochar have been used throughout history, Dhingra said. Ancient civilizations in Brazil used pyrolyzed organic biomass to improve soil fertility in the Amazon.
The biochar used in this study appears to be fine-grained coal. Its highly porous, carbon-rich characteristics facilitate improved water and nutrient exchange and can lead to reduced soil acidification when amended into the soil. It can be made from any kind of biomass, from manure to plant residues like corn stalks. In this case, Dhingra’s team used biochar made from wheat crop residues.
Research shows that organic soil amendments improve microbiome health, and adding biochar is a promising strategy for increasing soil fertility, beneficial microbial diversity and long-term carbon sequestration, he said.
The team characterized the effects of biochar-derived plant residues on tomato growth, soil microbial diversity and gene expression responses at the rhizosphere level in organically grown fruit.
Dhingra’s research team was led by Washington State University postdoctoral scholar Seanna Hewitt, Ph.D., in collaboration with Texas A&M postdoctoral scholar Rishikesh Ghogare, Ph.D. The team also included students from Texas A&M, Washington State University and a student from the University of California, Riverside.
“Biochar is useful for reclamation and further development of a millennia-old strategy to improve soil fertility,” said Dhingra. “This study provides an effective methodology to further investigate the impact of biochar and any other soil amendments on soil and plant health and potential uses in horticultural systems.”
The study showed increased beneficial microbial activity, numbers
Organically certified wheat-based biochar supplements were applied and incorporated into experimental sandy loam beds along with control beds at a rate of 2 tons per acre. All experimental beds were in certified organic soil.
Tomato transplants were placed in the biochar and control beds and received 5-1-1 Alaska Organic Fish Fertilizer once a week during the experiment. Rhizosphere samples were then taken at 25 days or juvenile stage; 40 days or vegetative stage of growth; 55 days or stage before flowering; and 70 days, with 75% of the fruit in a red ripe phase.
Dhingra said the researchers concluded that the soil microbiome showed increased functional activity in several beneficial microbes while decreasing the activity of pathogenic fungi throughout the study.
Conclusions are based on plant root responses and soil microbial community profiles. Active transcripts within communities were quantified at four plant developmental stages between emergence and harvest of mature fruits.
Transcription in plants is the process of decoding the DNA sequence of a plant gene, leading to the production of RNA, a molecule that represents the functional aspect of DNA. The study reveals that the microbiome can influence plant RNA and gene expression, Dhingra said, making biochar a potential enhancer of this symbiotic relationship when it comes to regulating critical plant developmental processes.
The study showed that biochar treatment increased gene expression in tomatoes due to the presence and number of beneficial soil bacteria or rhizobacteria compared to control plots. Enrichment analyzes revealed increased nitrogen cycling and degradation of organic compounds in the soil microbiome during the experiment.
“There is evidence that the plant and the microbiome were able to communicate better and modulate their function in the presence of biochar,” he said. “This modulation is important because a plant’s nutritional needs are known to change as the plant matures.”
A deeper look at biochar is needed
The protection of biochar plant roots from pathogens, such as fungal diseases, and the enrichment of tomato root performance, such as nitrogen metabolism, regulation of other metabolic processes, and organic compound production in the biochar-treated rhizosphere, were all positive results. Fruit yields and shoot fresh weights were not measurably improved by the biochar treatment, which was as expected in organic soils.
These early results provide a basis for measuring the biological impacts of biochar on different types of crops and soils under different management regimes. Further research could identify ways to optimize biochar application and its potential role in production across the horticultural spectrum, Dhingra said. Experiments are underway to similarly test biochar in a pecan orchard and vineyard.
“Not all biochar is created equal,” he said. “There are large structural and functional differences in biochars derived from different biomass sources, whether they are wheat cuttings, manure or hardwood. Plants respond differently to them, so we need to figure out what works best for pecan or wine grape growers, in home gardens or organic to conventional commercial production settings.
Dhingra said continued research is important as horticultural science continues to evolve beyond the goals of the Green Revolution, which focused primarily on yields. The goal now, he said, is to provide holistic approaches that link yield quantity and nutritional quality in ways that are economically and environmentally sustainable.
“The more we learn and understand about these natural soil-plant relationships, the more it informs our development of sustainable strategies to improve soil fertility and crop health across the spectrum of our production systems,” Dhingra said. “We need to produce 70% more food on 30% less land over the next two decades to meet food demand, and we want to make sure every centimeter of land remains highly productive.”