This research was conducted to investigate the impact of corn cob gasification biochar (CCGB), switchgrass pyrolysis biochar (SPB), turkey manure ash (TMA), and triple superphosphate fertilizer (TSP) on soil phosphorus (P) distribution in three agricultural soils from Minnesota, USA. Understanding how biochar can change soil P distribution is crucial to develop best management practices for recycling biochar products. Phosphorus sources were incorporated at rates of 0, 28, 56, and 84 mg P2 O5 kg–1 to 1.5 kg of each soil in 2-L pots. Corn (Zea mays L.) plants were grown (2 plants pot–1) in treated soils for 56 d after emergence. After 56 d, plants were harvested and soil samples collected for sequential P fractionation (H2 O, 0.5 mol L–1 NaHCO3, 0.1 mol L–1 NaOH, and 1.0 mol L–1 HCl) and enzymatic hydrolysis. The results of the sequential fractionation showed that CCGB and SPB were as effective as TSP and TMA at increasing total P extractable in water and HCl. In contrast, the increase in NaHCO3 and NaOH extractable total P was higher with TSP and TMA than with the CCGB and SPB. In most cases, the increase in inorganic P was similar between biochar and TSP, suggesting that biochar could supply equal amounts of plant available P as commercial fertilizer. The effects of biochar on enzymatically hydrolysable P were not consistent and varied by soil. In conclusion, the results of this study showed that biochar has potential to increase the available P pools in soils similar to commercial fertilizer.
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