Improving soil pH, nutrient concentrations, and enzyme activities by green manure returning in young and mature rubber plantation on Hainan Island, China.

Background: Studying green manure decomposition in various returning methods can establish a scientific foundation for farmland nutrient management. Methods: In a rubber plantation on Hainan Island, China, utilized the nylon mesh bag method to imitate the decomposition of kudzu (whole plant, stem, and leaf) under two returning methods (mulching and burying) in two different sites (young and mature rubber plantations). The study examined the decomposition rate and nutrient release dynamics of kudzu, as well as the effects of kudzu reintroduction on several soil properties including soil pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NO3−-N), ammonium nitrogen (NH4+-N), available phosphorus (AP), and enzyme activities. Results: Compared with mulching, the burying returning method significantly increased the kudzu decomposition rate and nutrient release proportions. After 270 days, more than 80% of the C, N, and P in different components of kudzu were released. The decomposition rate was found to be more affected by the initial soil factors than by the endogenous nutrients of kudzu. Compared with CK, all kudzu treatments led to significant increases in soil enzyme activities and soil pH, SOC, NO3−-N, and AP concentrations in two rubber plantations. The TN and NH4+-N concentrations were significantly increased in mature rubber plantations, while the TP was the opposite. Conclusion: The kudzu returned can effectively alleviate soil acidic, improve soil nutrient availability, regulating soil enzyme activities of the rubber plantation in the short-term. These results provide a scientific basis for the rational application of kudzu in rubber plantations. [ABSTRACT FROM AUTHOR]