Millet crops are typically cultivated in marginal, arid, and nutrient-depleted soils where environmental stress severely restricts agricultural productivity. As climate change intensifies land degradation, restorative soil management techniques are becoming essential for securing global food supplies. Biochar, a carbon-rich solid material generated through the thermal breakdown of organic biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More under oxygen-limited conditions, offers a resilient approach to revitalizing degraded farmlands. By systematically evaluating experimental findings across multiple millet species—including pearl, foxtail, finger, and proso millet—researchers Lopamudra Subudhi, Sandeep Kumar Behera, Alok Kumar Panda, and Shibani Mohapatra published a detailed review in the journal Discover Sustainability demonstrating how biochar amendments alter physical, chemical, and biological soil conditions to boost crop performance.

Physical soil structure experiences major enhancements following biochar incorporation. The porous architecture of biochar significantly lowers soil bulk density, reducing compaction by 15.9 percent in acidic oxisols and 10.3 percent in cambosols. When paired with standard inorganic fertilizers, bulk density in sandy loam soils drops from 1.28 to 1.08 megagrams per cubic meter. This reduction in compaction directly correlates with an expansion of total soil porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More from 45.76 percent to 58.93 percent. The creation of connected internal pore networks enhances soil aeration, reduces surface crusting, and increases water-holding capacity, resulting in soil water retention levels up to 200 percent greater than unamended controls. These physical alterations provide a looser soil matrix that supports improved root elongation, tillering, and overall water dynamics during prolonged dry spells.

The chemical properties of degraded growing media undergo equally substantial improvements upon biochar addition. Soil organic carbon increases across diverse soil types, with high-rate biochar treatments elevating organic carbon content from baseline values of 4.06 grams per kilogram to 16.5 grams per kilogram. Biochar acts as a liming agent in acidic soils, increasing soil pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More by up to 3.29 units while simultaneously boosting cation exchange capacity by 1.8 centimoles per kilogram. Nutrient availability rises dramatically across key macronutrients. Available soil phosphorus increases between 25.3 percent and 241 percent, available potassium increases by 53.2 percent to 513 percent, and extractable nitrogen levels experience consistent gains. Furthermore, biochar immobilizes heavy metals such as lead, cadmium, and zinc in contaminated soils, preventing toxic element uptake by crops.

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Biological activity within the rhizosphere expands significantly due to the habitat and carbon substrates provided by biochar. Microbial biomass carbon increases by 43 percent to 113 percent, accompanied by a 75 percent to 108 percent surge in soil basal respiration. Essential enzyme activities—including catalase, urease, alkaline phosphatase, and dehydrogenase—show marked increases, accelerating nutrient cycling and organic matter decomposition. These biological improvements enrich beneficial bacterial taxa such as Sphingomonas and Pseudomonas, which protect plants against environmental stress. The resulting synergy between physical structure, chemical nutrient supply, and microbial activity produces higher seed germination rates, superior stress tolerance, and substantial improvements in overall grain yield for millet crops cultivated in degraded agricultural lands.

Source: Subudhi, L., Behera, S. K., Panda, A. K., & Mohapatra, S. (2026). Biochar amendments as a regenerative agriculture strategy for soil health restoration and sustainable millet production. Discover Sustainability, 7, Article 4416.