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Volume 2008 (2008)
- Issue 106 Pages 106_1･･･
- Issue 105 Pages 105_1･･･
Volume 2008, Issue 106
Displaying 1-10 of 10 articles from this issue
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Original Article
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Toshihiro Tanaka, Takaaki Orita, Yutaka Uezono, Masamichi Kanno, Masaa ...2008 Volume 2008 Issue 106 Pages 106_1-106_14
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSIn order to reduce of the amount water used for protection of new shoots from frost,we examined a sprinkler system that could adjust the amount of water supply by choosing from several watering intervals depending on the surface temperature of tea plant canopy.
When the temperature of new shoots was lower than the critical level, our sprinkler system continued to supply water, and when the temperature was higher than the critical level, our system reduced the amount of precipitation.
In our study area, the temperature of new shoots was higher than the critical level,which was assumed to be -2.4°C during 3 examination seasons (from 2005 to 2007). Further,compared to a fixed interval sprinkler system, our system was found to be more effective in protecting the shoots from frost and in conserving water.
During the examination periods, the amount of water used by our system was about 40% of that used by the ordinary continuative sprinkler system, and it was about 80% of that used by the fixed interval sprinkler system.View full abstractDownload PDF (1452K) -
Takuya Araki, Kiyoshi Matsuo, Daisuke Miyama, Osamu Sumikawa, Shinsuke ...2008 Volume 2008 Issue 106 Pages 106_15-106_20
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSWe invested the influence of wind velocity fluctuation on air temperature difference between the fan (4.8 m) and ground levels (0.5 m) and the effect of frost protective fan operation in order to develop a new method to reduce electricity consumption due to frost protective fan operation. The results of the investigations are summarized as follows:
(1) Air temperature difference between the fan (4.8 m) and ground levels (0.5 m) was decreased following an increase in wind velocity, and the difference was less than 1°C for a wind velocity more than 3.0 m/s at a height of 6.5 m.
(2) When the wind velocity was more than 2-3 m/s, there was hardly any increase in the temperature of the leaves. In contrast, when the wind velocity was less than 2-3 m/s, an increase in the temperature of the leaves was observed.
Based on these results, it is possible that when the wind velocity is greater than 2-3 m, it prevents thermal inversion. Therefore, there would be no warmer air for the frost protective fan to return to the tea plants and the air turbulence produced by the frost protective fan would not reach the plants under the windy condition.View full abstractDownload PDF (1082K) -
Osamu Sumikawa, Daisuke Miyama, Takuya Araki2008 Volume 2008 Issue 106 Pages 106_21-106_38
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSSpray drift from tea field was measured by using water-sensitive papers(WSP).
1)Automated thresholding by "ImageJ", which is an open architecture image analysis program, was able to apply for extracting deposits on WSP. In order to analyze spot size of deposits and percent area coverage on WSP, the command of analyze particle was used. However, the stain area obtained by automated thresholding was larger than one by optimal threshold. The correction factor was 0.7411.
2)Although the spraying method and the nozzle type were different, 99% of the number of droplets was less than 200μm in the diameter and 80% was less than 125μm.
3)Among all nozzle treatments by manual spraying and by a riding type boom sprayer,bigger droplet size nozzles decreased drift, but there was no difference in droplet density on tea leaves.
4)Hydraulic application by a riding type boom sprayer was less spray drift than manual spraying, because a riding type boom sprayer can keep the distance from tea hedge canopy to a boom nozzle shorter than manual spraying.
5)Although the anti-drift cover for a riding type boom sprayer reduced drift when smallerdroplet size nozzle was used, bigger droplet size nozzle was recommended to use for avoiding drift risk.
6)Since the distance from tea hedge canopy to a boom nozzle can be short, the drift value (total droplet volume par unit area / sprayed volume par unit area) obtained in tea field was only 1/10 of the data reported by drift assessment in vegetable field.View full abstractDownload PDF (1063K) -
II. Seasonal Prevalence of Occurrences of Natural Enemies and the Relationship between the Host and the ParasitoidsAkihito Ozawa, Sakae Kubota, Shuji Kaneko, Shigeru Ishigami2008 Volume 2008 Issue 106 Pages 106_39-106_52
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSSpecies composition and the seasonal prevalence of natural enemies on the mulberry scale Pseudaulacaspis pentagona (Targioni) in tea fields in Shizuoka Prefecture of Japan were investigated by monitoring methods using yellow sticky traps hung on the branches under leaf layers. The species captured by the sticky traps were as follows: 5 species of parasitic wasps,Arrhenophagus albitibiae Girault, Pteroptrix orientalis (Silvestri), Thomsonisca indica Hayat (this species was identified as Thomsonisca amathus in Japan), and Epitetracnemus comis Noyes & Ren; 1 species of hyperparasites, Marietta carnesi (Howard); and 3 species of coleopteran predators, Pseudoscymnus hareja Weise, Chilocorus kuwanae Silvestri, and Cybocephalus nipponicus Endrody-Younga. Further, 1 Cecidomyiidae species (predatory gall midge), namely,Dentifibula sp., was captured by sticky traps. Among the parasitoids captured, A. albitibiae was the most abundant species, followed by P. orientalis. Among the predacious beetles captured, P. hareja was the dominant species. A. albitibiae demonstrated 5 or 6 peaks of seasonal prevalence in a year, and P. orientalis and T. indica exhibited 3 peaks of seasonal prevalence in a year. P. hareja and Dentifibula sp. demonstrated 3 indistinct peaks of seasonal prevalence in a year. The peak dates of A. albitibiae, P. orientalis, T. indica, and Dentifibula sp. were compared with those of the first instar larvae and adult males of the hosts, P. pentagona, which were captured by sticky traps. The relationships between the total numbers of each generation captured by sticky traps of the parasitoids A. albitibiae and the host P. pentagona over a period of 2 years revealed similar changes in the dynamics of the host-parasitoid models of Nicholson and Bailey (1935).This suggested that A. albitibiae was one of the most important natural enemies against P.pentagona in tea fields.View full abstractDownload PDF (1126K) -
Kunihiko Nonaka, Yuhei Hirono, Iriki Watanabe2008 Volume 2008 Issue 106 Pages 106_53-106_62
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSIn cultivation of tea plants, large amounts of nitrogen, compared to amounts used for other crops, have been used for fertilization, resulting in degradation of the soil environment between hedges and an increase in concentrations of nitrate nitrogen in surrounding water systems. To reduce the environmental load, new methods of fertilizer application are needed. This report deals with the effect of expansion of fertilization width on nitrogen recovery rate in tea plants.
In the test field, 15 N-labeled ammonium sulfate had been applied over custom fertilization by between-hedges fertilization (fertilization width of 15cm) and wide fertilization (fertilization width of 40cm), nitrogen recovery rates were compared. Expansion of fertilization width resulted in an approximately 30% increase in nitrogen recovery rate compared to that in the case of fertilization between hedges. Increases in nitrogen recovery rates were observed with fallapplied fertilization, spring-applied fertilization, pop-up fertilizer application, and summerapplied fertilization.View full abstractDownload PDF (829K) -
Nobuyuki Miura, Koji Uchimura, Takahisa Nakamura, Mitsuaki Karasuyama, ...2008 Volume 2008 Issue 106 Pages 106_63-106_70
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSSince 1999, the annual amount of fertilizer applied to tea fields has been restricted to 50 kgN/10a as much as possible to avoid nitrate pollution of groundwater; however, the nitrogen application tends to be similar to the previous high fertilizer levels to sustain high yields and superior tea quality in recent years. We investigated how this restoration of the previous heavy application affects nitrogen leaching and the forms of nitrogen in the soil.
According to our measurements, the increase in the application of organic fertilizer from 50 to 87-100 kgN/10a increased the concentration of nitrate leaching into underdrainage after ten months of heavy application. After another month, the nitrate concentration in the underdrainage reached the levels obtained previously under heavy application of organic fertilizer. This period (11 months) was six months shorter than the period required for the reduction of nitrate concentration to a prescribed plateau following the restriction of nitrogen application. Protein-like organic nitrogen in the soil increased one year after the heavy application of organic fertilizer with little increase in total nitrogen content. These results show that restoration of reduced nitrogen application to areas with previous heavy application rapidly increases nitrate leaching from the tea field with little increase in nitrogen accumulation in the soil.
Our results suggest that restoration of the previous heavy application of organic fertilizer has the effect of rapidly increasing nitrogen loading to groundwater in tea cultivation areas.View full abstractDownload PDF (1719K) -
Daisuke Miyama, Takuya Araki, Osamu Sumikawa, Kunimichi Higashi2008 Volume 2008 Issue 106 Pages 106_71-106_80
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSIn Japan, walking-type machines are widely used for fertilizer application in tea cultivation. The work strain of an operator using such a machine is high because the operator is required to walk along each hedge. Therefore, we have developed a walking-type fertilizer applicator equipped with 2 boom-type blow heads and 4 wheels. The decrease in the work strain was assessed by using the increase in heart rate as an index. While operating this fertilizer applicator, the operator walks between hedges, and air flowing through the boom-type blow heads causes release of fertilizer simultaneously onto the 2 rows. In order to assess the performance of the newly developed applicator, we determined the effective operating capacity, the increase in heart rate, and the relationship between the operating speed and the increase in heart rate with the developed, the conventional pushcart-type, and the conventional power fertilizer applicators. The results revealed that the effective operating capacity of the developed fertilizer applicator was 0.89 ha/h, which was higher than the operating capacities of the conventional fertilizer applicators. The increase in the heart rate of 6 operators using the developed fertilizer applicator was 20-52% less than that of operators using the conventional fertilizer applicators. At equal operating speeds of the fertilizer applicators, the increase in the heart rate of operators using the developed fertilizer applicator was approximately equal to that of operators using the conventional pushcart-type fertilizer applicator. Operators using the conventional power fertilizer applicator exhibited a significantly higher increase in heart rate than operators using other fertilizer applicators. At equal operating capacities, the increase in the heart rate of operators using the developed fertilizer applicator was significantly lower than that of operators using the conventional fertilizer applicators. On the basis of these results we can conclude that the use of the developed fertilizer applicator can considerably reduce the work strain of operators.View full abstractDownload PDF (978K) -
Shoichi Sato, Seiji Shinsho, Hiroyuki Iriki, Junya Asai, Hirofumi Suga ...2008 Volume 2008 Issue 106 Pages 106_81-106_90
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSWe developed a new parching machine with super-heated vapor or super-heated highmoisture atmosphere as a heat medium, and investigated the influence exerted on the characteristics of manufactured tea and crude tea quality.
(1)We developed machine specifications that improved throughput and allowed us to control stable quality compared with the conventional kamairicha parching machine.
(2)The new parching machine could not only manufacture like kamairicha but also achieve various degrees of steaming of products like green tea or heavily steamed sencha.
(3)The new parching machine could not only deactivate enzymes but dry leaves.
(4)The influence of throughput was great with respect to the grade of pan-parched flavour, which meant that there was a contact opportunity for tea leaves and the surface of machine's wall.
(5)Unpleasant smells such as that produced in a summer crop of tea were reduced by the new parching machine.View full abstractDownload PDF (1252K) -
Toyomasa Anan, Yuichi yamaguchi, Yasuaki Tamura, Yuzo Mizukami, Yusuke ...2008 Volume 2008 Issue 106 Pages 106_91-106_104
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSThe effects of air temperature on growth and constituents of new shoots in tea plants were examined.
In the first crop season, new shoots of tea plants grown in a hothouse from September to April of the following year were compared with those of tea plants outdoors. The average temperature in the hothouse from September to April of the following year was about 16-19°C,and the average outdoor temperature was about 9-12°C.
The results indicated that the coefficients of variation of the weights and numbers of immature leaves of new shoots grown in a hothouse were greater than those of new shoots grown outdoors. Therefore, the new shoots grown in a hothouse were more uneven than those grown outdoors. The catechin contents of new shoots grown in a hothouse were higher than those of new shoots grown outdoors, and total nitrogen contents of new shoots grown in a hothouse were lower than those of new shoots grown outdoors.
In the next study, young tea plants were cultivated in a hothouse and outdoors over a period of one year. The average temperature in the hothouse was about 22-23°C, and that outdoors was about 16-17°C.
The growth cycles in the hothouse were shorter than those outdoors, and the number of pluckings and the yield of new shoots grown in a hothouse were more than those of new shoots grown outdoors.View full abstractDownload PDF (811K)
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2008 Volume 2008 Issue 106 Pages 106_105-106_110
Published: December 31, 2008
Released on J-STAGE: November 01, 2011
JOURNAL FREE ACCESSDownload PDF (648K)
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