Biochar gives soil a healthy boost

"Biochar is useful for reclamation and further evolution of a millennia-old strategy to improve soil fertility," Amit Dhingra says. "This study provides an effective methodology for further examination of the impact of biochar and any other soil amendments on soil and plant health, and potential uses across horticultural systems." (Credit: Getty Images)

Biochar, an ancient soil amendment, could be a promising tool for future soil health enhancement and maintenance, according to a new study.

The findings show biochar improves the soil microbiome and plant root interactions with a spectrum of beneficial microorganisms found there.

“This is very relevant to horticulture production here in Texas because we have 1,300 soil types,” says Amit Dhingra, head of the department in the Texas A&M College of Agriculture and Life Sciences, Bryan-College Station. “It is proof-of-principle that shows biochar could be a valuable amendment when it comes to enhancing and managing soil health.”

Variations of biochar have been used throughout history, Dhingra says. Ancient civilizations in Brazil used pyrolyzed organic biomass to enhance soil fertility in the Amazon.

Biochar used in the current study looks like fine-grained charcoal. Its highly porous, carbon-rich characteristics facilitate enhanced water and nutrient exchange and may result in decreased soil acidification when amended to the soil. It can be made from any sort of biomass, from manure to crop residue like corn stalks. In this case, Dhingra’s team used biochar derived from wheat crop residue.

Research has shown that organic soil amendments improve microbiome health, and the addition of biochar is a promising strategy for enhancing soil fertility, beneficial microbe diversity, and long-term sequestration of carbon, he says.

The team characterized the effects of biochar-derived crop residue on tomato growth, soil microbial diversity, and rhizosphere-level gene expression responses in the organically grown fruit.

“Biochar is useful for reclamation and further evolution of a millennia-old strategy to improve soil fertility,” Dhingra says. “This study provides an effective methodology for further examination of the impact of biochar and any other soil amendments on soil and plant health, and potential uses across horticultural systems.”

The researchers applied and incorporated organic-certified wheat-based biochar amendments into sandy loam trial beds alongside control beds at a rate of 2 tons per acre. All trial beds were in certified organic soil.

Tomato transplants were placed in the biochar-amended and control beds and received organic 5-1-1 Alaska fish fertilizer once per week throughout the experiment. Rhizosphere samples were then taken at 25 days, or juvenile stage; 40 days, or vegetative growth stage; 55 days, or pre-flowering stage; and 70 days, with 75% of fruit at red ripe stage.

The soil microbiome displayed heightened functional activity in several beneficial microbes while reducing the activity of pathogenic fungi throughout the study, Dhingra says.

The team based their conclusions on the responses of plant roots and the soil microbial community profiles. Active transcripts within the communities were quantified at four plant developmental stages between emergence and mature fruit being harvested.

Transcription in plants is the process of decoding plant gene’s DNA sequence resulting in the production of RNA, a molecule that represents the functional aspect of the DNA. The study revealed the microbiome can influence plant RNA and gene expression, Dhingra says, which makes biochar a potential enhancer to this symbiotic relationship when it comes to regulating critical plant development processes.

The study showed biochar treatments increased gene expression in tomatoes due to the presence and number of beneficial soil bacteria, or rhizobacteria, compared to control plots. Enrichment analyses revealed increased nitrogen cycling and breakdown of organic compounds in the soil microbiome throughout the experiment.

“There was evidence that the plant and microbiome were able to communicate better and modulate their function in the presence of biochar,” he says. “That modulation is important as the plant’s nutritional needs are known to change as the plant matures.”

Positive outcomes included biochar protection of plant roots from pathogens, like fungal diseases, and enrichment of tomato root performance, such as metabolizing nitrogen, regulating other metabolic processes, and production of organic compounds within the biochar-treated rhizosphere. The biochar treatments did not measurably improve fruit yields and shoot fresh weights, which was as expected in organic soils.

These early results provide a foundation for measuring biochar’s biological impacts in various crop and soil types under different management regimens. Further exploration could identify ways to optimize biochar’s application and potential role in production across the horticulture spectrum, Dhingra says. Experiments are underway to similarly test biochar in a pecan orchard and a vineyard.

“Not all biochar is created equally,” he says. “There are major structural and functional differences in biochar derived from different biomass sources, whether that is wheat cuttings, manure, or hardwoods. Plants react differently to them, so we need to understand what works best for pecan growers or for wine grapes, in home gardens or organic to conventional commercial production settings.”

Dhingra says continued research is important because horticulture science continues to evolve beyond the aims of the Green Revolution, which primarily focused on yields. The goal now, he says, is to provide holistic approaches that bridge yield quantity and nutritional quality in ways that are economically and environmentally sustainable.

“The more we learn and understand about these natural relationships between soil and plants, the more it informs our development of sustainable strategies to enhance soil fertility and crop health across the spectrum of our production systems,” Dhingra says.

“We need to produce 70% more food with 30% less land in the next two decades to meet the food demand, and we want to make sure that every inch of land remains highly productive.”

The study appears in the journal Frontiers in Analytical Science.

Additional coauthors are from Texas A&M; Washington State; and the University of California, Riverside.

Source: Texas A&M University