GROWTH PROMOTION OF TEA TREES BY PUTTING BAMBOO CHARCOAL IN SOILTakehiko Hoshi
Department of Biological Science and Technology, School of High-technology for Human Welfare,Tokai University, Nishino 317, Numazu-shi, Shizuoka, 410-0395, Japan

Summary
To produce high-quality green tea with reduced amounts of agricultural chemicals and fertilizers, a10-year field experiment was started in 1998 to determine the feasibility of using bamboo charcoal in thesoil. The experiment, conducted in the eastern part of Shizuoka Prefecture, Japan, consisted of 8 plots withan actual cultivating area of 1,600m2.
Today, after three years of this experiment, the bamboo charcoal has tended to retain the supplied
fertilizers in the rhizosphere. The bamboo charcoal also tended to keep the soil pH in a range that was
suitable for the growth of tea trees. The heights and volumes of the tea trees in the plots in which thecharcoal was used were, on average, 20% and 40% greater, respectively, than they were in the negativecontrol. However, no differences were observed in the number of new shoots per tree or in the length ofnew shoots (stem length of three leaves and the shoot apex). The plot that had the best tea tree growth had
been treated with 100g crushed bamboo charcoal (particle size approximately 5 millimeters) per square
meter per year.
At this point in the experiment, the use of charcoal in the soil has not yet resulted in any clear
differences in key elements in the green tea product made from plucked new shoots.
Keywords
Cultivation, Field experiment, Reducing fertilizer use, Soil improvement
Introduction
The use of charcoal in farmlands is considered to be effective for improving the soil and promoting cropgrowth. However, there have been no long-term studies on the effects of charcoal on tea cultivation.
Abandoned Moso bamboo (Phyllostachys heterocycla (Carriere) Mitf.) forests with no economic value
are found near many farming villages in Japan. Moreover, the spreading of the bamboo trees remaining inthese forests is a problem because they interfere with the growth of surrounding trees and crops. It has been
proposed that the surplus bamboo could be put to practical use by making charcoal for cultivation.
Much fertilizer, especially nitrogen fertilizer, is used to produce high-quality tea in Japan. This has
increased production costs and caused environmental loading of nutrients (e.g., Okano et al., 1995).
Various methods for reducing fertilizer use by raising the efficiency with which fertilizers are retained by
the soil have been proposed. The use of coated urea fertilizer (e.g., Shiwa et al., 2000) is one such proposal.
Improving the soil with bamboo charcoal so that it better retains fertilizer has been proposed as anothermethod.
A long-term (10-year) field experiment was started in 1998 to clarify the effect of bamboo charcoal on
the growth of tea trees (Hoshi et al., 2001). A long-term experiment was needed because it takes over 10years for tea fields to fully mature and because the results of a short-term experiment could be masked byyearly fluctuations. Here I describe some of the results obtained in the first three years of this experiment.
Materials and Methods
A flat test field with a cultivating area of 1,600m2 was prepared. The surface soil was removed toprovide uniform conditions for each of eight plots (Table 1). The plots consisted of six small plots (S1-S6)
of 100 m2 and two large plots (L1 and L2) of 500 m2. S1 was a negative control. Two-year-old transplants
by cutting of two cultivars (Camellia sinensis var. sinensis cv. “Yabukita” and cv. “Okuhikari”) wereplanted in rows on March 15, 1998. The intrarow spacing was 0.5 m and the distance between rows was 1.8m, resulting in a transplant density of 1.11 m-2. Homemade bamboo charcoal was made by carbonizing
Moso bamboo at 300 - 400 °C in a Miura-type charcoal kiln. A commercially available charcoal was usedin S3 and S6. Table 2 shows the mineral contents of the charcoal as determined by particle induced X-rayemission (PIXE) analysis (Johansson et al., 1988). Two methods were used to apply the charcoal. In one
method, referred to as “single application” in Table 1, rough-crushed charcoal (5 – 10 cm in size) wasapplied a single time at the start of the experiment to the root zone (under ridges) at a density of 0.5 kg m-2.

In the other method, referred to as “annual application”, finely crushed charcoal (5 mm in size) was appliedannually in the spring in furrows at a density of 0.1 kg m-2 y-1. The amounts of fertilizer (N, P, and K) eachplot received during the first 3 years are shown in Table 3. The fertilizer use in each plot differed slightly
because of the use of different kinds of composite fertilizers (organic, inorganic, etc.).
Table 1. Specifications of the plots.
Charcoal use
TestingPrimary
Plot
CultivarArea
Quantity of dose
fertilizer
Origin(m2)(kg m-2)S1
Yabukita
100
Inorganic
S2Okuhikari
100
Inorganic
Bamboo (H)*0.50.1
S3
Yabukita
100
Inorganic
Bamboo (P)**
0.1
S4
Yabukita
100
Organic
Bamboo (H)*
0.5
S5
Yabukita
100
Organic
Bamboo (H)*
0.6
S6
Yabukita
100
Inorganic
Wood pulp waste***0.1
L1
Yabukita
500
Inorganic
Bamboo (H)*
0.5
L2
Yabukita
500
Inorganic
Bamboo (H)**: Homemade Moso bamboo charcoal. **: Commercial bamboo charcoal.
***: Commercial processing charcoal added fertilizer (N:P:K = 1.59%:2.14%:2.02%).

ApplicationSingle
AnnualAnnual
SingleSingleAnnualSingleTable 2. Mineral contents of homemade Moso bamboo charcoal as determined by PIXE analysis.
ElementMg
SiPS
ClKCa
Cr(ppm)2240.57
8001.22301.39344.832413.60
4299.80
480.46
5.43
ElementMn
Fe
Ni
Cu
Zn
Br
RbSr(ppm)
20.29
25.51
6.15
17.85
2.62
1.94
5.50
Standard element: Pd (1000 ppm) PIXE: Particle induced X-ray emission
Table 3. Amount of fertilizer applied to the eight plots.
PlotS1
S2
Element (g m-2)
NPKNP
Before planting
132 440
176132 440
1998
64
43
4364431999
66
5052
66
50
2000
64
4652
64
46
PlotS5S6Element (g m-2)
NPKN
P
Before planting
139 413176
142 3851998
4343434343
1999
66
565866
56
2000
64
4652
64
46K
176
4352
52
K
188
4358
52

S3
N
132
64
66
64
L1
N
133
65
3141P
440
4350
46K
176
4352
52

P
387
43
23
29K
176
432432

S4
N
139
4366
64
L2
N
133
64
30
41

P
413
4356
46K
176
43
58
52

P387
43
2329K
176
42
2332

To measure soil pH, dry soil was mixed with 2.5 times it weight of distilled water. The water was filteredand measured with a pH-meter. Soil electric conductivity (E.C.) was measured with an E.C. meter using
soil solution that had been filtered 5 times. The numbers of bacteria, fungi and yeast in the soil werecounted by the plate dilution method. Four indices were used to measure tea tree growth: tree height, tree
volume, and number of new shoots per tree and shoot length (stem length from node of the third leaf to theshoot apex). To determine water content, total nitrogen content and fiber content in new shoots, shoots werepicked and analyzed with a near infrared spectroscope (Hara et al., 1994). Total ascorbic acid and caffeine
contents in new shoot were determined by HPLC, glutamic acid and theanine contents were determinedwith an automatic amino acid analyzer, and tannin content was determined by the Folin-Denis method.
Results and Discussion
Soil pH and E.C. Figure 1 shows the soil pH and E.C. in each of the eight plots on December 30, 1998 andJune 30, 1999. The soil pH values of the plots that had charcoal in the soil were 1 to 1.5 pH units lower
than the pH in the control plot (S1) and were close to the range suitable for tea tree growth (pH 4.0-5.0).
The E.C. values in the charcoal plots were higher than the value in the control plot. This was thought to be
due to the charcoal in the soil retaining components of the fertilizer salts, because the testing conditions

30-Jun-99

5pH (H2O)
6730-Dec-98

E.C. (H2O) (μS cm-1)
60
120
180

except for the charcoal use were almost the same in each plot. No differences in the numbers of bacteria,
fungi and yeast in the soil were observed among the plots.

S1Fig. 1.

S2

S3S4S5Plot

S6

L130-Dec-98

S1L2S2S3S4S5Plot

30-Jun-99

S6L1

Soil pH and E.C. in each plot.
Boxes represent means (n = 15 for each of S1 to S6, n = 45 for L1 and L2) and error
bars represent ± standard deviation.

800

Table 4. Tea tree growth in each plot.
Number of new shoots
Shoot length
Plot
Tree height
Tree volume(shoots tree-1)
(cm)
(cm)
(103 cm3)
S1 (control)
68.6 ±16.3
304 ±160
25.3 ±6.1
3.4 ±1.0
S2
86.4 ±12.4*306 ± 85
19.3 ±5.3
3.7 ±0.8482 ±175*
23.0 ±6.6
3.7 ±0.8
S383.1 ±12.0*
593 ±187*
24.1 ±5.2
3.5 ±0.9
S4
93.9 ±10.5*580 ±188*
24.0 ±5.3
3.5 ±0.8
S5
96.5 ±11.5*
439 ±153*
26.2 ±6.4
3.5 ±0.8
S686.1 ±8.7*533 ±175*
25.6 ±7.4
3.7 ±0.9
L1
91.1 ±9.6*471 ±171*25.1 ±9.2
3.9 ±0.9
L283.8 ±13.8*
Year/Month
2000/11
2000/11
2000/92000/9Fifteen samples were used for S1 to S6, and 45 samples were used for L1 and L2. Values showmeans ± standard deviation. * indicates significance at 5% level.

S2S3S4S5S6L1L2033

Tea tree volume (10 cm )200400600

S11998/10

1998/11

1998/12

1999/7

1999/9 1999/11
Year/Month

2000/7

2000/92000/11

Fig. 2. Tea tree volume in each plot.
Boxes represent means (n = 15 for each of S1 to S6, n = 45 for L1 and L2) anderror bars represent ± standard deviation.

L2

Tea tree growth Table 4 shows the tea tree growth in the eight plots as measured by four growth indices.
Tree height and tree volume were significantly greater in the charcoal plots than in the control plot. Thetree volume and number of new shoots in S2 were relatively low, possibly due to the use of a different
cultivar (Okuhikari) in this plot. The difference in tree volume between the trees in the control plot andthose in the other plots except S2 appeared to increase with time (Fig. 2). Tea trees in S4, which had thegreatest tree volume, were visibly larger than those in S1 (Fig. 3). Tree height was an average of 20%
greater in the charcoal plots than in the control plot, and tree volume was an average of 40% greater. In
addition, among the charcoal plots, a reduction in the amount of fertilizer applied did not result in adecrease in tree growth. Tree growth tended to be greater with the annual application of charcoal than withthe single application, although the difference was not statistically significant.

Fig. 3. Side view and downward view of rows in the control (S1) plot and a charcoal plot (S4) on
December 15, 2000.
Ingredients of picked shoots
Table 5. Water content, total nitrogen content and fiber
Water content and total nitrogencontent in picked new shoots.
content were slightly higher in
Water content Total nitrogen content Fiber content
the testing plots receiving
Plot(%)(%)(%)
organic fertilizer (S4 and S5)
Ｓ1
4.3
6.9
14.8
than in the plots receiving
Ｓ2
4.5
6.6
16.8
inorganic fertilizer (Table 5).
Ｓ3
4.6
6.6
15.8
However, there was not a large
Ｓ4
5.5
7.4
13.7
difference in quality of the tea,
Ｓ5
5.4
7.1
15.0
as measured by total ascorbic
Ｓ6
5.3
7.0
15.5
acid, glutamic acid, theanine,
Ｌ14.86.8
16.7
caffeine and tannin, in the newＬ2
4.8
6.7
16.2
shoots between the negative
Samples were picked on May 2, 2000. Picked new shoots of 40 gcontrol plot and the charcoal
F.W. were dried by microwave oven and homogenized by grinderplots. Further studies of tea
before analysis.
quality will be needed todetermine the effects of charcoal. The effects, if any, will not be clear until the trees are more fully grown.
References
T. Hara and M. Matsumura (1994): Chemical properties of Japanese green tea analyzed by near infraredspectroscopy. Tea Research Journal, 79, 25-30 (in Japanese with English summary).
T. Hoshi, and T. Kaneko (2001): A practical study on bamboo charcoal use to tea trees, Report on researchby project, 13 (Field of technology integration: Activation of local community), 1-47, General Research
Organization of Tokai University Educational System (in Japanese).
S. A. E. Johansson and J. L. Campbell (1988), PIXE, John Wiley & Sons.
K. Okano, K. Matsuo and K. Chutani (1995): Response of young tea plant to nitrogen application inrelation to growth, photosynthesis and total nitrogen in new shoots. Tea Research Journal, 81, 1-8 (inJapanese with English summary).
M. Shiwa, K. Yoshizawa and M. Ito (2000): Dissolution of coated urea fertilizer and absorption of tea
plants in tea field soil. Tea Research Journal, 88, 31-38 (in Japanese with English summary).