Spearmint 507
is taken as a preceding crop the weed infestation in spearmint is found to be reduced
by at least 30%.
The chemical control of weeds has not become popular in spearmint, even though
some chemical herbicides, if applied 2–3 days after planting, (pre-emergence spray)
have been found effective. These herbicides include oxyflourefen (at 0.5 kg a.i./ha),
pendimethalin (at 0.75 kg a.i./ha) and diuran (at 0.5 kg a.i./ha). However, one should
bear in mind that no single weedicide can control all types of weeds and the optimal
rate of weedicides may vary with soil type and organic matter content of the soil.
Considering the fact that its oil is used in edible confectionery and general health
care, it is preferable to avoid the use of chemical herbicides in spearmint from a
safety viewpoint as well as the higher commercial value of organic products.
31.3.6 Crop rotations
Continuous cropping of spearmint in a field is not advisable as it leads to considerable
increase in weed population, soil-borne diseases and insects. One of the potent methods
of weed control is by growing the crops in sequences. Transplanting of paddy in a
crop rotation system not only minimizes weed interference but helps in reducing the
soil-borne diseases. The following rotations have been found quite economical and
are suggested for adopting.
- Maize – potato – spearmint.
- Early paddy – potato – spearmint.
- Late paddy – pea – spearmint.
- Maize – ‘Lahi’ (Brassica) – spearmint.
- Arhar (Cajanus) – spearmint.
- Paddy – spearmint.
31.3.7 Harvesting
Spearmint should be harvested in bright and sunny weather. The crop planted in
December becomes ready for first harvest during the last week of April in about 100–
110 days, the second harvest is taken in some varieties like Neer kalka (the most
popular Indian spearmint variety) between 60–70 days following the first harvest.
After harvesting, the green herbage may be spread under shade for a day for obtaining
good oil recovery (Singh et al., 1990; Singh and Naqvi, 1996). The yield of fresh
herb essentially depends upon the crop growth. A good crop of spearmint can give
20–30 t of fresh herb/ha. The yield of essential oil of spearmint ranges from 100–175
kg/ha depending on the crop growth and the cultivars used.
31.3.8 Organic cultivation
Organically grown spearmint oil is high value oil which finds wide uses in food,
flavour and aroma therapy. The right quantity of organic manure is an important
nutrient supplement component of organic farming system. The requirement of
organic manure depends upon the inherent properties of the soil, especially the organic
matter content of the soil. For instance, the forest soil being rich in organic matter
(more than 1.5%), it requires lower quantities of organic manures from external
source. The areas which are poor in organic matter should be provided adequate
amount of organic manures. Among the organic manures so far used in organic