From invasive weed to wonder-fertilizer: biochar from paper mulberry boosts mung bean growth

Scientists from Panjab University in India have developed a novel approach to simultaneously manage an invasive tree species and improve agricultural productivity. A new investigation demonstrates that biochar, a charcoal-like substance, created from the leaf litter of the invasive paper mulberry tree (Broussonetia papyrifera) significantly enhances the growth of mung beans (Vigna radiata). The research, led by Ipsa Gupta and Daizy R. Batish, explored two different application methods—a solid powder mixed into soil and a liquid water extract—revealing distinct benefits for crop development and soil quality.

A Tale of Two Biochars: Powder vs. Extract

The scientific team conducted controlled experiments in both laboratory and experimental dome environments to compare the effects of the two biochar forms. Powdered biochar was mixed directly into garden soil at concentrations of 0.5%, 1%, 2%, and 4%. For the alternative treatment, mung bean seedlings were irrigated with a water-based extract made from the same biochar concentrations. This comparative analysis allowed the researchers to assess not only if the biochar was effective, but also which application method provided the most significant advantages for the plants and the soil they grow in.

An analysis of the mung bean plants revealed that both forms of biochar promoted growth, but their optimal concentrations and specific effects differed. The powdered biochar produced the best results for overall plant growth and biomass, with a 2% concentration yielding the most substantial improvements. This method led to a remarkable 7% to 73% increase in root length and a 12% to 148% increase in total plant dry biomass compared to untreated plants. Applying the powder also significantly enhanced soil quality by increasing pH, moisture content, soil organic carbon, and the availability of essential nutrients like nitrogen, phosphorus, and potassium.

Cultivating Photosynthesis and Efficiency

A key distinction emerged when comparing the eco-physiological responses of the plants. While the powdered form was superior for soil health, the biochar extract had a more pronounced effect on the plant's metabolic functions at a lower concentration of 1%. Mung beans irrigated with the extract exhibited higher rates of net photosynthesis, transpiration, and stomatal conductance. This suggests that the nutrients in the extract are more immediately available to the plant, triggering a rapid physiological response. The quick uptake facilitates the transport of nutrients to the leaves, boosting the machinery of photosynthesis.

"Our findings present a compelling dual-purpose solution: we can effectively manage the invasive paper mulberry tree while simultaneously creating a potent soil amendment," states corresponding author Daizy R. Batish. "The powdered biochar acts as a long-term soil conditioner, enriching it with carbon and nutrients, while the water extract offers a fast-acting liquid fertilizer, which could be particularly valuable for short-cycle crops in urban farming settings. This research opens a new avenue for converting ecological challenges into agricultural assets."

From Urban Gardens to Future Fields

The results indicate that the choice between powdered biochar and extract depends on the agricultural goal. For long-term soil building and remediation, the powdered form is more advantageous. For systems requiring a rapid nutrient boost, such as in urban agriculture, hydroponics, or kitchen gardens, the extract is a highly effective option. At concentrations above 2%, the benefits for both forms began to decline, indicating that careful dosage is necessary to avoid alkaline stress on the plants.

The research provides a critical baseline for the sustainable application of biochar derived from invasive species. The authors suggest that future work should involve long-term field studies across different crop types and agroclimatic conditions to validate these promising results on a larger scale. This approach not only provides a method for improving food security but also proposes an economically viable strategy for managing invasive plants that threaten local ecosystems in urban and peri-urban areas.

Corresponding Author: Daizy R. Batish

Original Source: https://doi.org/10.1007/s44246-024-00112-5

Contributions: IG: Performed the experiment, Data Collection and analysis, Initial drafting and finalization; RS: Drafting, Analysis, Review and finalization; AK: Analysis, Review and finalization; HPS: Designing, Review and finalization; DRB: Conception, Designing, Review and finalization.