Biochar amendments as a regenerative agriculture strategy for soil health restoration and sustainable millet production

Abstract

Millet crops are primarily grown in marginal, nutrient-deficient, and increasingly arid regions, where declining soil health significantly limits productivity. Biochar is a carbon-rich byproduct of biomass pyrolysis that is being researched as a promising soil amendment to improve degraded soils. This systematic review has been conducted through an in-depth analysis of 14 peer-reviewed papers from 2014 to 2025, including a synthesis of the literature that describes the changes to soil physical, chemical, and biological properties, as well as the impacts on cultivar growth and grain yield that can be attributed to biochar amendment. Results indicate that biochar significantly reduces bulk density, improves soil porosity and water-holding capacity, and enhances soil structure, which are important and necessary indicators of soil for new millet establishment in sandy or compacted soils. In addition, biochar chemically increased organic carbon in soils, optimized pH levels, increased cation exchange capacity, and enhanced the availability of macro- and micronutrients. We also describe how biochar biologically increases microbial biomass, enzyme activities, and beneficial microbial taxa, while decreasing the effects of salinity and heavy metals via improved rhizosphere function. Constructively, these improvements contributed to better germination and root establishment, improved stress tolerance, and significantly greater biomass and grain yields for pearl, foxtail, finger, and proso millet. In summary, biochar is a viable, inexpensive, and climate-resilient practice for restoring soil functionality and increasing millet production in susceptible agroecosystems.