The kinetics curve of nitrogen mineralization from perennial leaves litter decomposed by earthworm (Phretima californica)

Abstract

The kinetics of N release during the process of decomposition of organic matter is influenced by organic matter quality, temperature, humidity, and decomposer. Acacia, coffee, salacca, and bamboo leaf litter are native plants and be the pioneer plants on the slopes of Mount Merapi after the eruption in 2010. However, there is a lack of information on the N mineralization process from the leaves litter of acacia, coffee, salacca, and bamboo. The study aimed to determine the kinetics of N release from the litter leaves of acacia (<em>Acacia decurrens</em>), coffee, salacca, and bamboo, which were tested with three approaches, namely zero order, first order, and second order. The experiment was carried out using 10 <em>Phretima californica </em>earthworms that were incubated with 35g of annual plant leaves at 25°C. The levels of NH₄⁺ and NO₃^- were measured at 0, 7, 15, 30, 45, 75, and 105 days after incubation by using the indophenol blue and derivative spectrophotometric method, respectively. Throughout the decomposition 105 days, the release of NO₃^- was higher than that of NH₄⁺ due to the nature of NH₄⁺ that was more easily immobilized than NO₃^-. The highest NO₃^-release in acacia litter (1.56 mg kg^-1) occurred 30 days after incubation, while in coffee, salacca, and bamboo occurred 105 days after incubation, reaching 1.92 mg kg^-1, 2.47 mg kg^-1, and 1.88 mg kg^-1, respectively. High N compound on the leaves litter unaffected to increasing total biomass earthworms in the end of incubation however promotes N mineralization rapidly. The kinetics of the second-order equation showed higher compatibility than the other equations to the N release with coefficient determination was higher. The kinetics of mineralization can be a strategy to use the leaves litter of perennial plants as sources of N nutrient input into soil.