In recent years there has been much interest in the production and use of biochars for application to soils. Biochars are biomass subjected to low-temperature burning under oxygen-limited conditions, called ‘pyrolysis’. The resulting mass is a low density, highly porous matrix (Figure 1) with more stable carbon degradation characteristics than most organic matter already in soils. 

Figure 1: Electron microscope image of biochar fragment, showing highly porous structure capable of retaining moisture, nutrients and microbes.

Until now much of the research efforts around biochars have been measuring or modelling potential soil carbon storage gains. However, there is now an increasing awareness of the potential role of biochars in improving soil and crop health. Biochars’ highly porous structure acts as an ideal home for soil microbes. This is because moisture is retained within the micro-pores of biochar and this ‘pore water’ contains dissolved nutrients and carbon which are feed sources for microbes.

Recent research publications highlight the combined benefits of applying biochars with nutrient-rich manures to soils. In this scenario, biochars act as a ‘sponge’ to help retain the nutrients provided by manure within the soil. Microbes feed on these more readily available nutrients, enhancing soil fertility and increasing crop yields (Figure 2). In addition, research also indicates that the effects on crops can be enhanced further with biochars that have been inoculated with mycorrhizae before soil application.

Figure 2: Soil with biochar (left) demonstrates enhanced moisture and nutrient retention, resulting in better crop growth than soil without biochar (right)

Overall, biochars have considerable potential to enhance soil and crop health if they are applied in the correct amounts to suitable soils.  

More details of these research trials can be found here: https://bsssjournals.onlinelibrary.wiley.com/doi/10.1111/sum.12997 

https://bsssjournals.onlinelibrary.wiley.com/doi/10.1111/sum.13068 

A comprehensive overview of Biochars for Environmental applications can be found here:

Biochar for Environmental Management