Effect of Bone Char Application on Soil Quality, Soil Enzyme and in Enhancing Crop Yield in Agriculture: A Review

Abstract

Soil quality, in contrast to air or water, exhibits a heightened level of heterogeneity and necessitates closer examination due to its impact on the well-being of flora, fauna, and human beings. Organic carbon is considered a fundamental indicator of soil quality, as it plays a significant role in strategies aimed at mitigating climate change. The generation of bone char arises from a thermochemical conversion process involving defatted bones. Specific attention is focused on the solubility of P compounds, which serves to classify bone chars as potential slow-release P fertilizers. The introduction of P into the soil can be enhanced through an "internal activation" process facilitated by the adsorption of reduced S compounds. Additional properties of agronomic significance originate from the porosity of bone char, which promotes water retention and provides a habitat function for soil microorganisms. The evaluation of soil quality has been a longstanding practice, involving an examination of physical and chemical characteristics such as pH, nitrogen levels, soil organic carbon, bulk density, accessible water, aggregate stability, particle size distribution, and soil structure. Recently, the concept of soil quality has been expanded to encompass the notion of soil health, which is perceived as a finite, non-renewable resource that undergoes constant change. Research also demonstrates the crucial role of soil biota in the assessment of soil quality, as they exhibit rapid responsiveness to disturbances. Animal bones undergo a process of defatting, degelatinization, and subsequent incineration at temperatures ranging from 600-800°C to produce bone char (BC). Reports indicate that typical BC contains 152 g P kg<sup>-1</sup>, 280 g Ca kg<sup>-1</sup>, and 6.5 g Mg kg<sup>-1</sup>, with carbon content typically falling below 100 g kg<sup>-1</sup>. The solubility of bone char in the soil depends on factors such as pH and the soil's capacity to absorb P, situating it within the range between rock phosphate and triple super phosphate (TSP). The application of bone char to the soil can enhance soil health, resulting in increased crop yield and improved quality.