Biochars and their feedstocks differ in their short-term effects in ameliorating acid soils grown with aluminium-sensitive wheat

Purpose Biochars have potential to reduce soil acidity and Al 3+ toxicity, and increase the availability of soil nutrients. This study aimed to compare the effectiveness of biochars and their raw feedstocks in amelioration of soil acidity. Materials and methods Ten ameliorants comprising of five biochars (pyrolyzed at 550°C) and their corresponding feedstocks (wheat chaff, canola stubble, vetch hay, lucerne pellets, and poultry litter) were added (1% of soil weight) to sandy Tenosol and loamy Chromosol with both having similar Al 3+ concentrations but Chromosol having nine times greater pH buffer capacity. The soils with the ameliorants were incubated for 7 weeks (incubation phase), before being planted with an Al-sensitive wheat (ES8) for 18 days (plant phase). Results and discussion Biochars outperformed their feedstocks in increasing soil pH, leading to a significant reduction of Al 3+ toxicity. Biochar additions increased shoot growth by 137‒341% for Tenosol and 10‒295% for Chromosol, whereas their feedstocks increased shoot growth by 25‒233% for Tenosol and -38‒136% for Chromosol. Poultry-litter biochar increased soil pH greater than the corresponding poultry-litter treatments by 1.59 units in the Tenosol and 0.79 units in the Chromosol at the end of the plant phase. In addition, all organic amendments (except wheat-chaff and its biochar) significantly increased shoot P concentrations with poultry-litter biochar achieving the highest Olsen P and shoot P concentrations in both soils. Evidently, high alkalinity and nutrient contents of poultry-litter biochar resulted in the greatest increases in soil pH and shoot biomass in both soils. Conclusions Biochars were more effective at ameliorating soil acidity than their corresponding feedstocks primarily via increasing soil pH and supplying plant nutrients, depending on soil type. Poultry-litter biochar was the most effective on both soils.