The new tea cultivar, ‘Shizukaori’, is a clonal cultivar suitable for processing green tea. ‘Shizukaori’ was selected from seedlings derived from crossbreeding the ‘Okuhikari’ (seed parent) and ‘Kuritawase’ (pollen parent) cultivars at the Shizuoka Tea Experiment Station (present: Tea Research Center, Shizuoka Prefectural Research Institute of Agriculture and Forestry, Kikugawa, Shizuoka, Japan) in 1989. It was selected by individual selection in 1997, designated as 89-2-7 (strain name) in 1998, and subjected to clonal tests from 1998 to 2003. It was subsequently evaluated for yield, specific characteristics, and local adaptability from 2005 to 2013. Test results showed both good yield and good quality of the processed ara-cha (unrefined tea); therefore, it was recognized as a superior green tea cultivar. It was later named ‘Shizukaori’. In addition, this cultivar was registered by The Plant Variety Protection System in 2015 and adopted as the recommended cultivar by the Shizuoka prefecture in the same year.

Shizukaori is a semi-early budding cultivar; the plucking time of the first crop is about 2 days earlier than that of the ‘Yabukita’ cultivar. The habit of the Shizukaori plant is that of the semi-upright type. The growth of the young tea plant is slow; however, as it becomes a matured plant, the growth rate improves and its vigor matches the Yabukita cultivar. Both the immature and mature leaves of this cultivar are elliptic in shape, with slightly thick leaves. The immature leaves are green in color, but the mature leaves show a darker green color and are glossy compared with Yabukita. The plant has the same or slightly lower resistance to midwinter freezing damage as Yabukita.

The Shizukaori cultivar is more resistant to tea anthracnose, caused by Colletotrichum theae-sinensis (Miyake) Yamamoto, than Yabukita. On the other hand, it is more susceptible to tea bacterial shoot blight (caused by Pseudomonas syringae pv. theae (Hori 1915) Young, Dye & Wilkie 1978) than Yabukita, although this depends on the research location. Further, Shizukaori is slightly more resistant to the insect white peach scale (Pseudaulacaspis pentagona (Targioni-Tozetti)), than Yabukita.

The plant yield at a young stage is lower for Shizukaori as compared to Yabukita. However, the yield of the mature Shizukaori plant is higher than that of Yabukita. The newly plucked shoots are abundant instead of being fewer, individually large, and heavy. The ara-cha (unrefined tea) quality of Shizukaori is comprehensively superior to Yabukita, and the aroma and taste of the first crop is especially excellent.

Shizukaori adapts to local conditions and is suitable for cultivation in any tea plantation in the Shizuoka prefecture. This cultivar is the most suitable one for a management body aiming at a high efficiency of management and at scale expansion by cultivar combination; it is also suitable for an area that focuses on branding, making use of the superior taste and aroma that this cultivar possesses.

Laboratory and field experiments were conducted to evaluate effects of insecticides on a leaf beetle, Demotina fasciulata Baly (Coleoptera: Chrysomelidae), of which adults damage young buds of tea plant. In the laboratory, fluxaemetamide, thiamethoxam, spinosad, spinetoram, dinotefuran and clothianidin showed 100 % mortality of D. fasciculata adults within one to four days after treatment, among 13 insecticides examined. In the field, significant reduction was observed in damage on buds and young leaves by D. fasciculata when tea plants were treated with fluxaemetamide, clothianidin, dinotefuran, acetamiprid, spinosad and chlorfenapyr. Control of D. fasciculata by using insecticide and/or the other methods is discussed for better organic farming of tea plant.

Gyokuro is cultivated in the shade and has green laver-like, hay-like and sweet odor. The aroma of gyokuro differs from that of standard sencha. To identify the key odorants isolated from gyokuro, the aroma in the headspace was extracted using three different types of solid-phase micro extraction fibers, followed by analysis using gas chromatography-olfactometry and mass spectrometry. Aroma extract dilution analysis (AEDA) was applied to fifteen products of gyokuro. Principal component analysis of the flavor dilution factors, obtained by AEDA, revealed that (Z)-1,5-octadien-3-one, dimethyl sulfide, 3-methylnonane-2,4-dione, 4-mercapto-4-methyl-2-pentanone, furaneol, and 2-acetyl-1-pyrroline were the potent odorants in the headspace above gyokuro.

A fertilizer application unit with a working speed-interlocking system for a riding-type tea field management machine was developed. The working speed-interlocking mechanism varies the number of rotations of the screw feeder in accordance with the working speed. The amount of discharge was found to be proportional to the rotation of the screw feeder. The speed-interlocking device could spread the fertilizer evenly in the field under a wide range of working speeds. The experimental results of the field test showed that the calculated field capacity using the prototype was 0.80-1.13 ha/h, and the effective field capacity was 0.24-0.29 ha/h. The actual application amount was 89-109% of the target application amount.