The application of biochar to soil offers multiple benefits in a wide range of agricultural systems. Biochars have been evaluated in various field crops and pastures around the world. Studies have found that biochars can improve plant yields, enhance soil water holding capacity and reduce fertiliser requirements, though results vary widely between different biochars, soil types, climates and target crops. Biochars have been shown to drastically improve plant productivity when applied to nutrient poor and degraded soils. Increases in agronomic yields of between 30% and 170% have been observed in tropical agro-ecosystems after the application of biochar. However, the biochar application rates often suggested in the literature for observing significant soil-related benefits are relatively high (≥10 t/ha) and therefore the large scale application of biochar is perceived as prohibitively expensive.
Pyrolysis causes volatilisation of a significant fraction of the N content in feedstocks, and may reduce the short- to medium-term availability of nitrogen and phosphorus. Nevertheless, feedstocks with high nutrient contents, such as manures, make biochar with higher fertiliser value than those with low nutrient content, such as wood. Furthermore, nutrients may be released relatively quickly upon decomposition of lower stability manure-based biochars compared to the higher stability woody biochars. Biochars made from green leafy material are expected to have intermediate nutrient value.
The uniqueness of the Biochar for Sustainable Soils (B4SS) project is based on the development of innovative formulations based on low application rates of biochar. This project will evaluate the potential effectiveness of biochar formulations, in comparison with other soil amendments for enhancing fertility, in a range of situations. There is potential for scaling up nationally and globally to other regions affected by similar conditions.