Ecoenzymatic stoichiometry reveals soil P limitation under biochar addition in a reclaimed mine area in Shanxi Province, China

Extracellular enzymatic activity plays an important role in carbon (C), nitrogen (N), and phosphorous (P) cycling, and consequently, serves as an indicator for soil function. However, microbial activities are inhibited in degraded lands due to nutrition limitations, which pose a challenge to ecological management. We investigated the effects of maize biochar addition (1, 3, and 5%) on soil and enzyme stoichiometries in a post‐mining area in Shanxi province. The results showed that soil organic C and total N increased significantly with increasing biochar addition, leading to significant increases in soil C:P (by 157.9%) and N:P (by 76.1%) under 5% of addition. Biochar addition stimulated enzyme activities significantly, and the maximum of enzyme activities occurred in treatment of 5% addition. Soil enzyme C:N increased significantly following biochar addition, while enzyme C:P and N:P decreased at 5% biochar addition. Vector analysis indicated that microbial activity tended to be limited by soil N before addition, whereas it was limited by P availability at high biochar addition. This was mainly because that biochar addition could promote sorption of P and lower P bioavailability in soil. Our research suggested that biochar application could substantially improve soil nutrition status and microbial activity in infertile land, however, it would likely result in imbalances between substrate stoichiometry and microbial demand. The result might provide a reference for the management of biochar application during soil restoration.