How Biochar & Soil Bacteria Protect Hemp From Salt Stress

As climate change, drought, and poor irrigation practices continue to increase soil salinity worldwide, farmers are facing a difficult question: how can crops survive and still produce high-quality compounds under environmental stress? For the hemp industry, this challenge is especially important because salt stress can reduce plant growth, cannabinoid production, and terpene yields.

Research¹ published in the journal Plant Science suggests that the answer may lie beneath the soil surface. The findings highlight how soil biology could play a major role in the future of sustainable hemp cultivation. Let’s dive into this groundbreaking study and what it means for the future of cannabis and hemp cultivation.

How Salt Stress Harms Hemp Plants

Salt stress occurs when excess salt accumulates in soil, making it difficult for plants to absorb water and nutrients. This problem is becoming more common in agricultural regions affected by drought, irrigation runoff, and rising temperatures.

For hemp plants, salty soil creates several cascading problems. One of the biggest is phosphorus deficiency. Phosphorus is a critical nutrient involved in energy transfer (ET ), root development, photosynthesis, and the production of secondary metabolites such as cannabinoids and terpenes. When salt levels rise, phosphorus becomes harder for plants to access. As a result, hemp plants may experience:

• Reduced growth
• Low chlorophyll production
• Poor water retention
• Oxidative stress
• Declining cannabinoid and terpene levels

In the study, researchers exposed hemp plants to 100 mM sodium chloride, a level designed to simulate salinity stress. Unsurprisingly, stressed plants showed lower biomass, reduced essential oil production, and lower concentrations of cannabinoids such as CBD and THC. However, the researchers also tested possible solutions, biochar and phosphorous-stabilizing bacteria.

What is Phosphorus-Solubilizing Bacteria?

Phosphorus-solubilizing bacteria, often shortened to PSB, are beneficial microbes that help convert unavailable phosphorus in soil into forms plants can absorb more easily. In healthy ecosystems, these bacteria naturally work alongside plant roots. They help unlock nutrients trapped in soil particles, improving nutrient uptake and supporting plant resilience during environmental stress.

The researchers used two bacterial strains in the study:

• Bacillus subtilis
• Pseudomonas putida

Both are well-known plant-friendly bacteria often studied for their ability to improve soil fertility and stress tolerance. Rather than acting like synthetic fertilizers, these microbes function more like biological partners, helping plants access nutrients already present in the soil while also supporting root health and water balance.

How Biochar Supports Soil Health

Biochar has gained growing attention in sustainable agriculture over the past decade. It is a carbon-rich material created by heating organic matter in low-oxygen conditions, a process called pyrolysis. Because of its porous structure, biochar can improve soil in several ways. It helps retain water, enhances microbial activity, improves nutrient storage, and increases soil aeration.

In the study, researchers used phosphorus-enriched biochar, also called P-biochar. The material was mixed into the soil at a concentration of 2% by weight. The idea behind combining biochar with beneficial bacteria is that biochar creates a supportive environment where microbes can thrive while also improving nutrient availability. Together, the two amendments may help plants better withstand harsh growing conditions.

Hemp Growth Improved Under Salinity

The results of the study were striking. When hemp plants were treated with phosphorus-enriched biochar and beneficial bacteria together, they performed significantly better under salt stress compared to untreated plants.

Plants treated with bacillus subtilis plus biochar experienced a 25% increase in shoot weight and a 28% increase in root weight compared to plants exposed only to salinity. Meanwhile, the combination of pseudomonas putida and biochar increased root weight by an impressive 38%.

The treatment helped hemp plants continue developing healthy root systems even in salty soil. Stronger roots are critical because they improve water uptake and nutrient absorption during stress conditions. The treated plants also maintained higher chlorophyll levels and better leaf water content, indicating healthier photosynthesis and hydration.

Cannabinoid Production Increased

Perhaps the most exciting finding for hemp growers was the effect on cannabinoid production. Salt stress alone reduced cannabinoid levels, which is consistent with previous research showing environmental stress can interfere with secondary metabolite synthesis. However, with the combined biochar and bacteria treatments:

• CBD levels increased by up to 13%
• THC levels increased by up to 16%
• Essential oil yield increased by as much as 49%

This suggests that improving soil biology may help hemp maintain not only plant survival, but also chemical quality under difficult environmental conditions. For cultivators focused on cannabinoid extraction, terpene preservation, or premium flower production, that could have major implications.

Why Oxidative Stress Matters

The study also examined oxidative stress, which plays a major role in plant damage during salinity exposure. When plants experience stress, they often produce excessive reactive oxygen species, unstable molecules that can damage cells, membranes, and proteins. One marker researchers measure is malondialdehyde, or MDA, which reflects cellular damage caused by oxidative stress.

The researchers found that hemp plants treated with biochar and beneficial bacteria had significantly lower MDA levels compared to untreated salt-stressed plants. At the same time, the treated plants showed higher levels of proline, a protective compound plants naturally produce during stress. Proline helps stabilize cells, maintain water balance, and protect proteins from damage. Together, these changes indicate the treatment helped hemp plants better regulate stress internally rather than simply masking symptoms.

Soil Microbes May Shape Hemp Quality

The hemp industry often focuses heavily on lighting systems, genetics, nutrients, and climate control. While those factors are important, this study highlights another major variable that may shape cannabinoid and terpene production: the soil microbiome.

Plants do not grow alone in nature. Their roots interact continuously with bacteria, fungi, and organic compounds that influence nutrient availability and stress responses. Researchers are increasingly discovering that beneficial microbes can alter plant chemistry in meaningful ways. In hemp, soil microbes could influence:

• Cannabinoid expression
• Terpene profiles
• Stress tolerance
• Water efficiency
• Yield consistency

As environmental pressures increase globally, soil-focused cultivation strategies may become increasingly valuable.

Sustainable Hemp Farming Solutions

The findings also fit into a larger movement toward regenerative and biologically driven agriculture. Traditional synthetic fertilizers can sometimes worsen soil degradation over time, particularly in regions already dealing with salinity issues. Biochar and beneficial microbes offer a more sustainable approach that works with natural soil processes rather than against them. Biochar also has environmental appeal because it can store carbon in soil for long periods, potentially contributing to carbon sequestration efforts.

While the study was conducted under greenhouse conditions and still requires field validation, the results are promising for growers searching for environmentally friendly ways to protect crop quality.

The Future of Stress-Resistant Hemp

Hemp cultivation is expanding into regions where water scarcity and salinity are becoming increasingly common challenges. Maintaining cannabinoid and terpene production under these conditions will likely become a major priority for the industry.

The research suggests that soil biology could be part of the answer. By combining phosphorus-solubilizing bacteria with phosphorus-enriched biochar, researchers were able to help hemp plants maintain growth, hydration, and secondary metabolite production despite salt stress.

The study reinforces a growing scientific understanding that healthy soil is not simply a growing medium. It is a living ecosystem capable of influencing plant resilience, chemistry, and overall crop performance. For hemp growers, the future of cannabinoid production may depend as much on microscopic soil allies as it does on genetics or lighting systems.

References:

^{1. Arezoo Shekari, Marzieh Ghanbari Jahromi, Ali Akbar Ghotbi-Ravandi, Vahid Abdossi, Ali Mohammadi Torkashvand, Phosphorus-solubilizing bacteria and phosphorus-enriched biochar enhance growth, cannabinoid content, and essential oil yield in salt-stressed hemp (Cannabis sativa L.), Plant Science, 2026, 113208, ISSN 0168-9452, https://doi.org/10.1016/j.plantsci.2026.113208}