Biochar amendment changes the effects of nitrogen deposition on soil enzyme activities in a Moso bamboo plantation

Abstract

ABSTRACTSoil enzymes are the metabolic motors for soil organisms. However, how soil enzymes respond to biochar amendment in plantations under increasing chronic atmospheric nitrogen (N) deposition is poorly understood. In this study, we analyzed the effects of N deposition (30, 60, and 90 kg N ha−1 yr−1 for treatments N30, N60 and N90, respectively) and biochar amendment (20 and 40 t ha−1 for treatments BC20 and BC40, respectively) on six soil enzyme activities (β-fructofuranosidase, cellulase, nitrate reductase, nitrite reductase, urease, and acid phosphatase) in a Moso bamboo (Phyllostachys edulis (Carrière) J. Houz) plantation. We found that N deposition significantly decreased the β-fructofuranosidase activity in the N30 and N90 treatments (P < 0.01) and urease activity in N90 (P < 0.001), but not those of the four other tested enzymes (ns). BC40 amendment alone significantly decreased urease and acid phosphatase activities (P < 0.01). Biochar amendment neutralized the negative effect of N deposition on urease activity. Our results suggest that N addition could decrease soil pH to reduce urease activity and change the limiting factor for β-fructofuranosidase activity from N to carbon (C). The adsorption capability of biochar to soil N nutrient elements could decrease urease activity to limit the utilization of N; meanwhile, biochar addition could aggravate phosphorus (P) limitation to repress acid phosphatase activity. However, biochar addition could increase soil pH to promote urease activity. These findings provide new insights into the effects of biochar amendment on soil enzyme activities in plantations that suffer from the effects of N deposition.