Biochar is superior to lime in improving acidic soil properties and fruit quality of Satsuma mandarin.

A better understanding is required for using biochar as an alternative option to lime materials for sustainable amelioration of soil acidity and improvement of fruit quality in acidic soils. In this study, a pot experiment was conducted to investigate the comparative effects of biochar (three different dosages of biochar, 1%, 2% and 4%, were denoted by BC-1, BC-2 and BC-3, respectively) and lime (three different dosages of lime, 1.2, 2.4 and 3.6 g kg, were denoted by L-1, L-2 and L-3, respectively) on soil properties and fruit acidity of Satsuma mandarin. The decreased rates of fruit titratable acid (TA) by BC-1, BC-2 and BC-3 were 16.18%, 25.00% and 14.71%, which were higher than those by L-1, L-2 and L-3 were 11.76%, 16.18% and 5.88%. Moreover, the increased rates of fruit total soluble solid (TSS)/TA were 14.94%, 31.73%, 28.04% by BC-1, BC-2 and BC-3, but were 11.42%, 21.77%, 10.15% by L-1, L-2 and L-3, suggesting that biochar had better effects on improving fruit quality. Acidic soil properties were improved by biochar and lime, but biochar had better amelioration effects, as evidenced by soil-treated with BC-2 and BC-3 had greater increases of soil pH, soil respiration (SR) and microbial metabolic quotient, activities of soil urease (SU), invertase (SI), catalase (CAT) and cellulose (SC), and concentrations of soil phosphorus (P), potassium (K) and magnesium (Mg). Principal component analysis showed that soil pH, SR, SU, SI and CAT were main contributors to the differences of improvement effects of biochar and lime. Correlation analysis showed that fruit TA had negative relationships with soil pH, SU, SI, CAT, SC and soil P, K, Mg. This study indicates that the better effects of biochar on improving fruit quality of Satsuma mandarin were associated with the greater effects of it on improving acidic soil properties.