Soil management practices in coffee-based agroforestry systems within Universitas Brawijaya Forest impact on maintaining soil carbon stock

Abstract

Farmer fertilization practices is one of effort on climate change mitigation and determine environmental services of agroforestry systems especially soil carbon stocks. The research aimed to assess soil carbon stock in smallholder agroforestry systems within Universitas Brawijaya (UB) Forest, East Java. The study was conducted on two different types of fertilizer application (e.g., organic, mixed organic and inorganic fertilizer) with three different doses of organic fertilizer (e.g., 5, 10, 15 kg tree-1) and 3 replications of each, totalling 18 plots. At each plot, soil sample was collected at fertilized and unfertilized areas with a depth 0-20 cm and 20-40 cm, then measured total organic C, soil bulk density, soil pH, and soil carbon stocks. Application of mixed fertilizer had 19-42 % lower of soil organic C as compared to those in application of organic fertilizer, resulted in decrease of soil carbon stock around 15-41 % at a depth 0-40 cm. In addition, the increases dose of organic fertilizer application up to 15 kg tree-1 decreased soil bulk density at 0-20 cm depth of soil around 8-10% as compared to dose 5 and 10 kg tree-1. Our study suggested to optimize fertilization practices for maintaining soil fertility and its relationship to coffee production.