INTRODUCTION
Rosemary herb is versatile and is used extensively used in British
and Italian cuisine. The plant has a delightful fragrance, nutmeg odour and a rather bitter flavor. Rosemary herb
belongs to the family Lamiaceae and there are several species with different
chemical composition specific to different origins. Its is used to flavour
meats, sauces and vegetable dishes. It is also used for its anti-oxidant
properties in industrial manufacture of meat based products. Its oil is
widely used in hair shampoos, bath essences, cosmetic, perfumes and insect
repellents.
CLIMATIC REQUIREMENTS
This is a perennial crop and can survive for a long time in
one site. Rosemary herb does well at high altitudes and requires neutral to slightly
alkaline soil, hence the need for lime if soil pH falls
below 6.5. The soil should
be light and well drained.
PROPAGATION
Propagation by farmers who grow Rosemary herb in Kenya is preceded by selection of the right cultivars. To ensure retention of desired characteristics, Rosemary herb should only be propagated vegetatively.
12.15cm long tip cutting should be taken from young shoots and leaves from the
lower half removed, the base of the stem dipped into a rooting powder and the
cutting buried 8-10cm in a sandy nursery bed at a spacing of 20x20cm. Under
irrigated conditions, cutting can be taken all year round but there is need for
co-ordinated planting schedules. Plant should be transplanted to the fields at
4-6 months as bare root plants. Under rain-fed condition, preparing cutting and
field planting is best carried out during the rainy season. Planting should be
at a spacing of 120x45 cm resulting to a plant population of 20-30 thousand
plants per ha.The objective is to produce a dense bush 60cm in diameter
with vigorous shoot growth.
CROP MANAGEMENT
The first harvest is taken when plants are 18-24 months old. Prior to this shoots should be cut back to promote growth and prevent the formation of long, woody stems. When plants are mature, shoots should be cut back by 10-15cm twice yearly to reduce the formation of woody stem. Straggling branches should be pruned hard to promote the production of new shoots. After harvesting, the plants should be ridged up lightly. Weed control should be done regularly as required.
FERTILIZER REQUIREMENTS
Application rates of fertilizers depends on the fertility of
the site. A standard annual application rate of 60kg/ha N, 25kg/ha and 75kg/ha
K applied as three equal dressings for N and K and single application for P is
required. During planting, the first of the N and K dressing and all of P
should be applied during as basal fertilizer and cultivated into the soil. An
addition 50 kg/ha N can be applied during the first year to promote vigorous
growth and establishment. Top dressings should be banded along the rows.
PEST AND DISEASES
There are no significant pest and disease problems experienced by those who grow rosemary herb in Kenya.
HARVESTING AND YIELDS
A single harvest is done yearly with the first harvest 18-24
months after planting. For production of fresh o dried herb, harvesting is done
before flowering, while for essential oil extraction, the crop is cut at
flowering. The crop is cut just above the hard wood, which must not be
introduced into the still as it taints the oil. Fresh yield range between 8-12
ton/ha producing 2-2.5 tons/ha dried rosemary herb. Fresh product should be stored at
0.5-1.5c and 95-98% relative humity
PROCESSING
DRIED ROSEMARY HERB
The crop should be dried immediately after cutting to avoid
loss of the volatile oil and colour. The crop should be dried on racks in the
shade. There are no firm recommendation for temperature regimes in artificial
dryers, but it is suggested that a maximum temperature of 43 c should be used.
ROSEMARY OIL
The oil usually obtained from the dry material by
distillation, although the fresh material can also be used but is more bulky to
handle. Volatile oil content of the crop varies under different environmental
condition and with the particular characteristics of the cultivar. Oil content
of the fresh material ranges from 0.3-1.5% and an oil yield of 40-60 kg/ha can
be expected. The character of the oil is affected by the method of distillation
and the length of storage of the plant material prior to distillation. The oil
can also be extracted using ethanol or benzine, either directly on fresh
material, or on the dried herb after distillation, to give products used as
anti-oxidants.
Grow rosemary herb in Kenya as it is fitting considering climate and soil conditions.
Grow rosemary herb in Kenya as it is fitting considering climate and soil conditions.
