Biochar-Based Fertilizers: A Smart Solution for Sustainable Agriculture

The improper management of agricultural waste leading to environmental pollution is a glaring problem of our age. One of the possible methods to mitigate this problem is the conversion of surplus agricultural biomass to low volume, high value products like biochar-based slow-release fertilizers. Over the last few decades, the use of biochar as a soil amendment has increased due to its high surface area, porous structure, surface functional groups, and recalcitrant carbon content. However, improper use may lead to reduced availability of nutrients in soil. To remedy this, biochar may be transformed to a slow-release fertilizer by adsorption of nutrients with the added advantage of minimal leaching loss compared to traditional fertilizers. The properties of biochar-based slow-release fertilizers vary based on the source material, pre-treatment of biochar if any and synthesis methods like co-pyrolysis, adsorption, palletization, or encapsulation. The diverse range of pore sizes in biochar makes it an ideal matrix for loading nutrients such as nitrogen, phosphorus, potassium, and micronutrients. The rate of release of nutrients from biochar matrix and its mechanism are influenced by the process like adsorption–desorption, pore geometry, microbial activity, and stability in the soil. Biochar-based fertilizers have the potential to boost crop production and increase nutrient use efficiency. Utilizing biochar-based fertilizers represents a beneficial strategy in context of sustainable agriculture as it helps reduce nutrient losses while simultaneously increasing crop yields.