Nutrient Loss from a Tea Plantation Area in Japan

Abstract

A great amount of fertilizer is applied to tea plantation area to improve the quality of the product in Japan. Field surveys on water quality of a small river whose watershed includes tea plantation fields and questionnaire survey to the owners in the area were carried out to make clear the runoff characteristics of nutrients, both nitrogen and phosphorus, from a small watershed including the tea plantation area, and to estimate the annual budget of the nutrients. The concentrations of nitrate and phosphate in the stream water in dry period through the tea field were up to 8.09mgN/L and 0.065mgP/L respectively, which were more than 10 times higher than those in the upstream water which run through the forest. Seasonal variations of the N concentrations and P concentrations in dry periods were observed which were independent from the timing of fertilizer application. During a storm event, the concentrations of phosphate, particulate phosphorus and particulate nitrogen increased while those of nitrate decreased. Large amount of nitrogen fertilizer, 620kgN/ha/year, was applied to the tea plantation area in a year and it was estimated that only 12% of the nitrogen input was recovered as harvest product and 86 % of the input was discharged downstream through the river. 55kgP/ha/year of phosphorus fertilizer was applied to the area in a year, and it was estimated that 10 % of the phosphorus input was recovered and 38 % discharged.