Objectives Green manure mulching is one of effective practices to enhance soil organic matter content, alleviate soil acidification and improve the balance of nutrients. Kudzu (PuerariaIobata) is a common legume green manure in rubber plantation. Full understanding the effect of kudzu mulching is needed for its efficient application in rubber plantation.

Methods In a young rubber plantation in Danzhou, Hainan Province, the fields were mulched with and without (bare land) Kudzu mulching for 4 years. The soil samples were collected in layers of 0–10 cm (top layer) and 10–20 cm (sub layer) for measurements of soil bulk density, pH, water content, soil organic carbon (SOC), total and available N, P and K contents, and six soil enzyme activities (sucrase, catalase, β-1,4-clucosidase, urease, leucine aminopeptidase and β-1,4-clucosaminidase).

Results 1) Compared with bare land, Kudzu mulching increased SOC by 4.2%–5.9%, total N by 9.1%–11.8% and total P by 12.0%–38.1%. The increase ranges of SOC and total N in top layer were higher than those in sub-layer, while that of total P was opposite. The pH was significantly enhanced in top soil but decreased in the sub-layer than those in bare land, respectively; 2) Under kudzu mulching, the catalase and urease activities in top soil layer were increased and the increased range was 327.8% and 108.1% of the bare land in the same soil layer, respectively. There were insignificant impacts of Kudzu plantation on activities of β-1,4-clucosidase, β-1,4-clucosaminidase and leucine aminopeptidase in both the soil layers; 3) Under kudzu mulching, soil catalase activity was positively correlated with total N and total K but negatively correlated with readily available K (P < 0.05). Sucrase activity was negatively correlated with total N, pH, total K and available P (P < 0.05). In bare land, catalase activity was negatively correlated with NH₄⁺-N, urease activity was significantly and negatively correlated with SOC and readily available K but significantly and positively correlated with pH and total K; sucrase activity was negatively correlated with pH and total K, but positively correlated with available K and SOC; both β-1,4-clucosidase and β-1,4-clucosaminidase activities were negatively correlated with NO₃^–-N (P < 0.05).

Conclusions Kudzu mulching is efficient to increase the soil organic C, total N and total P contents, which is helpful to alleviate soil acidification in the top soil, improve soil activities of catalase, urease in top layer, thus enhance soil fertility especially in 0–10 cm soil layer in young rubber plantation.