Recent research highlights how particle size affects the availability of phosphorus (P) in biochar produced from the solid fractions of manure-based digestates. This study explored the immediate P availability in soils treated with biochars of varying particle sizes—powdered or pelleted—across different soil types.

Biochar from digestates is considered a sustainable fertilizer option due to its high P content and potential for transport to P-deficient agricultural regions. However, the form in which biochar is applied significantly impacts its effectiveness.

Key findings revealed that powdered biochar enhanced the immediate availability of P compared to pelleted forms. Fine particles allow for better soil contact and root access, resulting in improved crop P recovery and biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More production, as demonstrated in pot experiments with spring barley. In contrast, pelleted biochar showed lower P recovery due to limited interaction with soil particles.

Moreover, the study found that soil type plays a role in biochar efficacy, with finer biochar particles offering a pronounced liming effect in acidic soils, which could improve overall soil fertility.

These results underscore the importance of optimizing biochar particle size to maximize its short-term fertilizer potential. While fine biochar particles enhance P availability, considerations such as dust emissions and transport efficiency must also be addressed. Future research should explore long-term effects and field-scale applications to better inform biochar management practices.

This study supports a circular approach to managing P from agricultural waste, contributing to sustainable nutrient recycling and soil health improvements.