Agriculture Reference
In-Depth Information
1.2 Ceylon Tea
The tea plants (
Camellia sinensis
(L.) O. Kuntze) which belong to the genus ca-
mellia probably originated in China. First record of tea dates back to 350 BC in a
Chinese dictionary, however, according to Cha Pu, tea drinking started only in the
6th century. The habit of tea drinking later spread to Japan, Portugal, Holland and
Europe. In 1834, the British started the cultivation of tea in their colonies. As a sub-
stitute crop for the dreaded coffee in Sri Lanka, tea was introduced in 1867 by James
Taylor. However, tea was first planted in Royal Botanical garden in Peradeniya way
back in 1839. After the experimental plantings, first tea plantation Loolecandera
Estate was established in Kandy district (Nathaniel
2008
).
One of the oldest tea producing country, Sri Lanka produces predominantly black
tea (about 95 %) and is well known as “Ceylon tea”. It is ranked among the best tea
in the international market. In recent past, Ceylon tea was categorized as world's
cleanest tea considering its low pesticide residues, therefore the brand name of Cey-
lon, guaranteed the quality. According to Ziyad and Zoysa (
2008
), tea production
in the country grew at an average annual rate of about 10 % during last decade
and at present the production is 315 million kg. Low-country (0-600 m amsl) tea
production is significant and it contributes about 60 % to the total tea production of
the country. The rest two regions, mid-country (600-1,200 m amsl) and upcountry
( > 1,200 m amsl) contribute about 16 and 24 %, respectively. However, 53 % of the
estate lands are under old seedling tea and rest 47 % under VP tea. About 90 % of
the seedling tea was older than 60 years. Hence, overall productivity of the country
remains less compared to other tea producing countries (Anon
2003
).
The yield of tea is from the tender young shoots comprising either two or three
leaves with a terminal bud. Tea crop is determined by the shoot population density,
size of the shoots and the rate of shoot extension. Hence, these factors are widely
studied by many scientists to determine the yield (Wjeratne
1996
; Odhiambo et al.
1993
; Tanton
1992
,
1981
). However, the number of harvestable shoots per unit area
and mean dry weight of single shoot is largely responsible for the tea yield.
Studies have been carried out by several scientists to demonstrate effects of differ-
ent environmental components on yield. Balasuriya (
1999
) showed the effect of mean
air temperature on shoot development, Wijeratne (
1996
) exposed the effect of satura-
tion vapour pressure deficit, temperature and soil moisture deficit on shoot popula-
tion. Apart from environmental factors, crop management practices and environment
stresses (biotic and abiotic) affect the agronomic yield or total weight of harvested
crop. Thus, yield is a multivariate function and hence, estimation of yield is a puzzling
task. However, it is essential for the decision-making process at different levels.
1.3 Primary Production and Yield
Primary production is the process which converts light energy or solar radiation into
chemical energy. Basically, green plants are called primary producers because they
