Abstract
In this study, in order to clarify the characteristics of the newly developed sewage sludge fertilizer (NSSF) using sewage sludge and regional biomass for tea cultivation, the optimum fertilization amounts (ratios) of NSSF, the optimum fertilizer application period, and the amount of nitrogen leaching to groundwater were investigated. In the tea cultivation test using the NSSF, the tea yields were equal to or better than those of the conventionally fertilized areas, indicating that the NSSF can replace rapeseed cake (conventional organic fertilizer) as a fertilizer (24kgN/10a fertilization out of the maximum annual fertilizer nitrogen amount of 50kgN/10a). The concentration of metals and heavy metals in the NSSF-fertilized soil did not change significantly during the tea cultivation tests, and the values were below the soil environmental standard. When NSSF was fertilized in spring or autumn/spring, the fresh leaf yield and crude tea quality were equal to or better than those of organic mixed fertilizer were obtained. Compared with the control (conventional organic fertilizer), the NSSF had a lower nitrate nitrogen concentration in the infiltrated water (fertilization in autumn and spring : 15-30mg/L, control: 35-100mg/L), indicating that the environmental load is lower than that of the conventional farming system.
