Influences of the kind of soil at tea field and amount of applied nitrogen fertilizer on yield and quality of tea, and on utilization rate of applied nitrogen fertilizer
2010
Yano, K., Kagawa-ken. Agricultural Experiment Station, Takamatsu (Japan) | Ikeuchi, H. | Kawata, K.
The influences of the kind of soil at tea field and amount of applied nitrogen fertilizer on yield and total nitrogen content in the tea as well as on utilization rate of applied nitrogen fertilizer was investigated over the periods 1985-1992 (tree age 5-12), 1999-2001 (tree age 19- 21), and 2003-2008 (tree age 23-28). Total nitrogen content served as a quality indicator. 1. The yield of the first crop of 5-12-year-old tea trees was higher in the granite soil and diluvian soil than in the Mitoyo formation soil The yield of the first crops of 19-21-year-old and 23-28-year-old tea trees was highest in the diluvian soil, next in Mitoyo formation soil and lowest in the granite soil. Total nitrogen content in the first tea crops were similar regardless of the kinds of soil and amount of nitrogen fertilizer applied. No evidence of quality deterioration caused by use of low-nitrogen fertilizer was found. 2. Yield and total nitrogen content of the second tea crop was comparable to those of the first crop regardless of tree age examined (age 5-11. 19-20, and 23-27). 3. The utilization rate of nitrogen fertilizer (amount of taken out nitrogen/amount of fertilizer nitrogen applied) was highest at tree age 19-20, intermediate at tree age 23-27, and lowest at tree age 5-11. Excessive application of nitrogen fertilizer appeared to be a cause of the low utilization rate at tree age 5-11. An increase in the amount of taken out nitrogen and low nitrogen application resulted in a high utilization rate at tree age 19-20, while a gradual decrease in amount of taken out nitrogen and low nitrogen application resulted in an intermediate utilization rate at tree age 23-27. These findings suggest that reduced nitrogen application is effective for improving the utilization rate of nitrogen fertilizer. 4. In summary, reduced application of nitrogen fertilizer did not result in a deterioration of yield and quality, but improved the efficiency of fertilizer application. Therefore, an annual application of 20 kg/10a of nitrogen fertilizer is sufficient for fields annually producing around 1,000 kg/10a of raw tea leaves.
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