Effect of Nitrogen-Content in Soil on Uptake of N-Manure by Tea Plant

Abstract

The effect of soil nitrogen upon the uptake of fertilizer nitrogen by tea plants was studied by using ¹⁵N-manure.
One-year-old plants were transplanted into pots containing three soils of different nitrogen contents in May. After growing for 6 weeks in a green house ¹⁵N ammonium sulphate (10.3 atom %) at the rates of 100, 200, and 400 mg N per pot together with 0.9 g of potassium phosphate (monobasic) was supplied to tea plants.
These plants were grown for additional 5 weeks (untill their new shoots develope) and then digged out. The plants were divided into new shoots, matured leaves, trunk and branches, and roots, and subjected to chemical and isotope analyses after airdrying, weighing and pulverizing. Soil samples were also taken for chemical determination.
The results obtained were as follows ; With increase in total nitrogen content of soils, dry weights and total nitrogen contents increased considerably in new shoots and whole plnat parts. Therefore, it was shown that the nitrogen uptake by the plants from both of the fertilizer and soil increased greater in soil of high nitrogen content than in soil of low nitrogen content. However, the contribution of fertilized N to the total nitrogen content of the plant was decreased with increase in total nitrogen content of soil.
These results suggested that the increase in nitrogen uptake by the plants in soils of high nitrogen content might be due to the increase in nutrient absorption activity, which could be improved by absorption of soil nitrogen.