Objective  Effects of biochar application on the physiology of Fokienia hodginsii seedlings under drought stress and enzyme activities in the soil were investigated.

  Method   Corn-stalk biochar was added in varied rates to the irrigation-controlled potting soil in cultivating one-year-old F. hodginsii seedlings. Growth and osmotic regulator contents of the seedlings as well as enzyme activities in soils containing the biochar at 20 g·kg⁻¹ (T1), 50 g·kg⁻¹ (T2), or 80 g·kg⁻¹ (T3) along with a blank control (CK) were determined.

  Result   (1) All biochar applications significantly promoted the seedling growth and biomass accumulation (P＜0.05) with T2 showing the greatest increases on plant height, root diameter, and per plant biomass. (2) Under draught, the contents of soluble sugar, soluble protein, and proline in the seedlings of the treatment groups increased initially followed by a decline. In 42 d, soluble sugar and proline peaked, so did soluble protein in 56 d. The overall effect by the treatments ranked T2＞T1＞T3＞CK. The seedlings grown on T2 had 50.7% more soluble sugar, 127% more soluble protein, and 54.4% more proline than those on CK. (3) The treatments also significantly elevated the enzyme activities in soil (P＜0.05). Specifically, urease activity reached the maximum in 70d, catalase, nitrate reductase, and sucrase activities in 42d, and sucrase content in 56 d. Of all treatments, the effects ranked T2＞T1＞T3＞CK. Again, T2 was the top performer.

  Conclusion   Short of adequate water supply, biochar addition at a rate of 50 g·kg⁻¹ significantly boosted the enzyme activity in the soil and benefitted the growth and stress resistance of the seedlings grown in the field. On the other hand, an addition beyond that level could be detrimental.