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EFFECTS OF FERTILIZER APPLICATION ON THE LEVELS OF NUTRIENTS OF XYLEM SAP OF TEA PLANTS

 Akio MORITA and Mitsuiku IWAHASHI
  Shizuoka Tea Experiment Station
Kurasawa, Kikugawa-cho, Ogasa-gun,Shizuoka 439,Japan

ABSTRACT 

The growth and nutrient concentration of xylem sap were examined of 15-year old tea plants grown on standard-fertilized (SF) and fertilizer-free (FF) fields. The doses of NPK were 540,180.27kg/ha/year. Xylem sap was sampled the cut-end of stems (5 mm, 10 cm under the plucking surface) by means of vaccum blood sampling cylinders, for 4hours on rainy days form March to July 1990.

The Growth and nitrogen concentration of both the first and second crop of SF were higher than those of FF.

The amounts of xylem sap collected during the period almost exceeded 2 ml which sufficed for the analyses. The pH values of xylem sap ranged 5.2-6.3 which declined at the first and second flush. While EC values peaked during the same periods. The levels of total amino acids, phosphoric acid and potassium of tea sap also peaked at the first and second flush but remained low in other stages. Their concentrations of the first flush were much higher compared with those of the second.

Higher levels of total amino acids were observed in xylem sap of SF than in that of FF suggesting that the dressing of nitrogen increase.

INTRODUCTION

It is well known that the amount of translocation of nutrients from roots to above-ground parts affects much on the yield and quality of the plant. Therefore, works have been done on nutrients of the sap of xylems of many plants 1,2,4). In the case of tea plants, similar studies have been pursued and reports have been made on the movement of nitrogen elements within the plants 3.6). However, there is a few case of sampling sap in tea fields 5) and there is no information on the seasonal fluctuation of nutrients of the sap of tea plants. This has been because the tapping of sap required special apparatus and electricity for vacuum pump and therefore could not be performed at any suitable locations and it took time to install the apparatus. The authors, for this reason, contrived a few anywhere. By trying its practical use, it is confirmed that this device can tap enough amounts of tea sap for analyses.

Thus, by using the kit, the sap of tea plants was sampled from the tea fields with different ferilizer treatments from March to July. and the seasonal fluctuation of the levels of nutrients in the sap as well as the effect of fertilizing were examined.

MATERIALS and METHODS

 Standard-ferilizer (SF) and fertilizer-free (FF) plots were established in the tea field (16-year old. c.v. YABUKITA) of Shizuoka Tea Experiment Station since 1986. No fertilizer was applied in the FF plots and NPK (540-180-270kg/ha/year) was applied in the SF plots. Other management practice was indentical for the both treatments.

The first and second crop of both treatments was plucked on 1st. MAY and 23rd. June 1990 respectivly. 6 squarerot (20 x 20 cm) samplings were made from each treatment and fresh weight of the samples was regarded as the amount of growth. The samples were then dried and pulverized for analyses.

The sampling of xylem sap was done in the method shown in Fig.1. The kit consisted of a vaccum blood sampling cylinder (20 ml, 135 mmhg, NIPRO & CO. LTD), a holder of the cylinder, a needle, an inlet packing of gas chormatograpghy equipment and a Teflon tube. 5 kits were set on the shoots with diameter of 5 cm (10 cm blow the plucking surface) at one time and sap was collected for 4 hours from 9 AM to 1 PM. The amounts of sap. pH and electric eonductivity (EC) were measured immediately after the collection. and the sap samples were frozen and stored for analyses. sap was analyzed for amino acid by colorimetric method 7), phosphoric acid by liquid chromatograthy and potassium by atomic absorption spectrophotometer. 

RESULTS AND DISCUSSION

As shown in Table 1. the SF treatment gave higher amounts of growth and total nitrogen than the FF treatment and the effect of fertilizing was evident.

It was impossible to sap with this kit during the fine daytime, while it was possible during the nighttime and rain. It was considered that this was because evaoratin activity of free foliage was much more vigorus than sucking ability of the cylinder and sap was consumed by foliage during the fine daytime. Therefore, sampling of sap was made during rain when its success was assured. FIg.2 shows sufficient amounts of sap were collected for analyses throughout the period. There was no difference on the amounts of sap between the treatments but they appeared affected much by weather condition at sampling. 

The pH values of sap ranged in the weak acid area of 5.2 to 6.3 and tended to come to the lowest around the first and the second harvest. And more lowering of the values was oberved in the in the SF treatment, suggesting that the levels of nutrients related to the dressing were higher as new shoots grew.

The EC values of sap began to increase at bud opening and peaked at the harvests and declined thereafter. The EC values of the SF treatment were higher than those of the FF treatment and influence of the fertilizing was observed.

Both amino acids and phoshoric acids in sap gradually increased from the time of bud opening and peaked around the harvesting period (Fig.3.4). Potassium co



 

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