Organic Matter Inputs Enhance Soil Carbon and Nitrogen in Coffee Smallholder Plantations

SOIL ORGANIC CARBON (SOC) and Total Nitrogen (TN) are vital in influencing soil characteristics and determining soil fertility and productivity. Generally, coffee farmers in Sumbermanjing Wetan, Indonesia, use inorganic fertilizers for a prolonged period, resulting in low SOC and TN values. Therefore, a study was carried out to assess the impact of organic material application on: i) soil physical characteristics, ii) Soil organic carbon (SOC), and iii) Total Nitrogen (TN). The research was conducted using a Randomized Complete Block Design with five treatments, namely i) control (P1); ii) goat manure inserted into biopores (P2); iii) compost inserted into biopores (P3); iv) Gliricidia green manure inserted into biopores (P4); and v) goat manure applied on the soil surface. The variables examined in this research were soil physical characteristics (bulk density, porosity, and mean weight diameter), soil organic carbon, and total soil nitrogen. The study revealed that organic soil amendment have the capability to improve soil physical characteristics, reduce soil bulk density and increase soil porosity, although not significantly different. Addition of manure (P2) and Gliricidia green manure (P4) significantly increased soil aggregate stability (p<0.05). Furthermore, the addition of organic materials also increased soil SOC values, although not significantly different. The addition of manure (P2) at a depth of 20-40 cm, and Gliricidia green manure (P4) significantly increased total soil nitrogen (p<0.05). Future studies are necessary to investigate the lasting impacts of applying organic materials on these soil properties.