Concentration and fractionation of phosphorous in soils with acidulated pig biochar

To determine the effect of addition of acidulated pig biochar on phosphorus (P) availability and fractionation in soils, an incubation experiment was carried out using a randomized complete block design having five treatments:an untreated control(ck), acidulated pig biochar, raw pig biochar, single superphosphate, and calcium magnesium phosphate, with three replications. Each amendment was mixed with soil at 0.1% (w/w) and placed in a plastic pot. Soil samples were taken from each pot after a 210-day incubation period to assess P fractionation using modified Hedley's sequential extraction procedures. A correlation analysis was also included. Results showed that, compared to ck, electrical conductivity (EC) of the soil increased (P superphosphate > calcium magnesium phosphate > raw pig biochar. The percentage of stable P pools decreased (P < 0.05) with addition of the amendments, and the proportion of the stable P pools was negatively correlated to the proportion of labile (R2=0.86, P < 0.01) and moderately labile (R2=0.94, P < 0.01) P pools. The acidulated pig biochar treatment significantly (P < 0.05) increased the concentration of all P fractions and maintained a relatively low proportion of stable P in the treated soil. In conclusion, with significant differences in soil P concentrations and fractionations between acidulated pig biochar and chemical P fertilizers treatments tested, it would be potentially viable to use acidulated pig biochar as an alternative P fertilizer and substitute for superphosphate and calcium magnesium phosphate in agricultural production.