Yield evaluation of tea (Camellia sinensis) clones grown in Pontevedra (NW Spain)

Vela P.¹, Paz C. ¹, Mansilla P. ¹, Salinero C. ¹, Sainz M.J. ²

¹ Estación Fitopatológica de Areeiro, Diputación de Pontevedra, Subida a la Robleda s/n, 36153 Pontevedra, Spain. E-mail: pilar.vela@depo.es
² Departamento de Producción Vegetal, Universidad de Santiago de Compostela, Campus Universitario s/n, 27002 Lugo, Spain

Introduction

      Camellia sinensis is the species most widely cultivated of the genus Camellia, and the most important economically, since the tea beverage is obtained from its shoots. It is an evergreen shrub with bright green leaves, and blooms in autumn (Figure 1). It has been cultivated in Asia for more than 3,000 years, where it was used for medicinal purposes. However, it became popular and a widely consumed beverage (Jiyin et al, 2005). Nowadays, it is the second most widely consumed beverage in the world, after water (Hicks, 2009).
      Around 89% of the area used to cultivate tea is located in southeastern Asia (FAO, 2002). The main tea producers are China, with 1,499,900 ha, yielding more than 1,620,000 tons a year, and India with 600,000 ha with 966,000 t (FAOSTAT, 2011). Other important tea producers are Kenya, Sri Lanka and Indonesia. In Europe there are some tea plantations in Azores (Portugal) but for consumption it is mainly imported from India (FAOSTAT, 2011).
      Depending on the degree of fermentation of the shoots, once they are collected and dried, the tea is classified into three groups: green tea (without fermentation), oolong (semi-fermented) and black (fermented) (Hicks, 2009). Although in         Figure 1. Camellia sinensis plant             Europe the fermented tea is the most consumed, in Eastern countries the green and semi-fermented tea are the most popular, depending on the area.
      Camellia sinensis grows at sea level and up to 2,200 m high (De Costa et al., 2007) and it develops better in acid soils, with a pH ranging from 4.5 to 6.5 (Zhen et al., 2002). Its development is favoured by abundant rainfall and mild temperatures, ranging from 18 to 25°C (De Costa et al., 2007). Temperatures lower than 13°C and higher than 30°C reduce shoot growth (Carr, 1972; Watson, 1986; Carr & Stephens, 1992).
      In Galicia (NW Spain), camellias have been cultivated as ornamentals for more than 200 years: the majority of plants growing in public and private gardens are Camellia japonica cultivars. In this region there are no commercial plantations of C. sinensis, but there are isolated plants cultivated as ornamentals in some gardens.
      The soil and climate in Galicia, with its acid and well-drained soils rich in organic matter, mild temperatures and high relative humidity, are perfect for the cultivation of the species of the genus Camellia, which flourish with little attention, reaching sizes higher than those in their places of origin (Samartín & Pérez-Samartín, 1988; Salinero & Vela, 2004), thus tea commercial production may be an alternative for the cultivation of this species in this region of Spain.
In the camellia research centre Estación Fitopatolóxica de Areeiro located in Pontevedra, Spain there is a small experimental plantation of C. sinensis (Figure 2).
      The aim of this work is to assess the potential of tea production in an experimental plantation of C. sinensis clones in Pontevedra province and to select those with a higher yield so as to establish further commercial plantations in Galicia.

                                                                              Figure 2. Camellia sinensis plantation in Pontevedra (Spain)

Material and methods

      A plantation of 48 clones of Camellia sinensis in a 250 m2plot located in the Estación Fitopatolóxica de Areeiro (Pontevedra, NW Spain) was studied. The plot was bordered to the east and to the north with a kiwifruit plantation (Actinidia deliciosa), and with another plantation of ornamental camellias (cultivars of C. japonica and C. reticulata) to the west. The main characteristics of the soil were: pH 5.7, O.M. 5.0 %, NaHCO₃-extractable P 59 μg/g, and assimilable K content 140 μg/g.
      Tea plants were grown from seeds in pots, with a mixture of sand and peat, in a nursery under natural light and temperature conditions. In 2009, healthy four-year old plants (one of each clone) were planted 2 m apart and 1.9 m between rows. The plantation was covered with a mesh and in order to avoid any water stress in plants, sprinkler irrigation was applied every year at the end of spring and during the summer. Due to the high fertility of the soil, the plot received no fertilizer.
      In September 2012, a shape pruning was carried out on all plants. The potential of shoot production of each clone was estimated during 2013. Shoot collection was started the first week of February when the first shoots were observed in some clones and it ended at the beginning of November. During harvest, all new shoots were collected by hand on a weekly basis. The number of shoots obtained per plant was counted and the fresh weight of the total number of shoots of each clone was measured in order to establish the weekly production of shoots. In addition, for each clone the average weight of the shoots and the annual shoot production was determined.

Results and discussion 

      Only 5 clones started to develop the first shoots in the first week of February 2013 and this production continued every week until the first week of November. Most clones developed shoots from the first week of April until the middle of November, but the number of shoots produced per clone varied between weeks (Figure 3). 

Figure 3. Number of tender shoots collected per month in every Camellia sinensis clone cultivated in Pontevedra (Spain)

      The weight of fresh shoots produced per clone weekly varied greatly among collection periods. Four periods of maximum yield were established for all clones: the first in May, the second in the first half of July, the third in the month of August, and the last one in the second half of September, July being the month with the largest production (Figure 4). These results were similar to others recorded in Galicia on the shoot development of C. japonica cultivars. The number of shoots produced reached a peak in spring and summer (Vela et al., 2013).
      Differences were observed in the quantity and in the weight of shoots produced per clone (Figures 5 and 6). Three clones (EFA-7, EFA-9, EFA-90) yielded less than 250 shoots that weighed less than 140 g. Six clones (EFA-3, EFA-10, EFA-108, EFA-109, EFA-111, EFA-119) developed more than 1,750 shoots, and three of them (EFA-10, EFA-108, EFA-119) recorded a higher fresh weight (1,100-1,200 g). Most clones developed 750-1,250 shoots a year, weighing from 400 to 700 g.

Figure 4. Fresh weight (g) of shoots collected per week from the 48 C. sinensis clones in 2013. The black lines of the graph correspond to the three plants with an annual tender shoot production of more than 100g (EFA-10, EFA-108 and EFA-119)

      The six most productive clones were those in the experimental plot next to a kiwifruit orchard that was fertilized every week, from the middle of May to September, alternating calcium nitrate and manganese with potassium nitrate. Probably the differences observed among clones could be related to the application of nitrogen fertilizers in the kiwifruit plantation, since the soil of the tea plantation was rich in P and K. It has been estimated that the production of 1 kg of tea leaves requires 45-65 kg N (Bonheure, 1991). Therefore further research is needed to determine the production potential of all the tea clones studied, so as to establish a homogeneous fertilization system in all plantation rows.

Figure 5. Accumulated number of shoots per year and per month collected from each Camellia sinensis clone cultivated in Pontevedra (Spain)

Figure 6. Monthly and annual accumulated weight (g) of the shoots collected from each C. sinesis clone

Conclusion

      Camellia sinensis plants cultivated in Pontevedra (NW Spain) develop shoots for tea production, mainly from April to November, with maximum production in July. The most productive clones were EFA-10, EFA-108 and EFA-119, yielding 1100-1200 g of fresh weight per plant. The nitrogen fertilization applied in the nearby kiwifruit orchard next to the C. sinensis plantation could favour clone production.

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