Drug crops: crops that are used for the preparation of medicines, for instance e.g. tobacco, mint etc.
Narcotics: Crop plants or their products that are used for stimulating, numbing, drowsing or relishing effects such as tobacco, ganja, opium poppy, anise etc.
Mint (Mentha spp)
The genus Mentha consists of about 25 species, of which better known species are
Japanese mint (M.arvensis L. var. piperascens Holmes)
This species yield the oil of Mentha on steam distillation, which is the raw material, required for the manufacture of menthol. Menthol is used as a flavouring agent, anti-pruritic, and coolant and as a carminative.
Pepper mint (M. piperita L)
Peppermint is a perennial, glabrous, strongly scented essential oil yielding plant and native of Mediterranean countries. The oil is used in the pharmaceutical and flavouring industries.
Common or spear mint (M. spicata L.)
Scotch spear mint (M.cardiaca Baker)
The spear mint (M.spicata) formerly called as M.virdis is having carvone (70 to 80%) as its chief constituents. The oil is widely used in pharmaceutical industry and also as a flavouring and sweetening agent.
Bergamot mint (M. citrata Ehrh.)
Mentha citrata Ehrh commonly known as bergamot mint yields aromatic oil on distillation, which is rich in linalool and linalyl acetate. The oil is one of the classic perfume materials.
Japanese mint prefers a cooler climate than a hot tropical or semi tropical climate and good sunshine during its harvesting. Deep, fertile, loose, moist soil, with pH of 6 to 7.Peppermint requires temperate to subtropical climate can withstand frost also. It grows on a wide range of soils, but thrives best in deep well drained soils rich in organic matter. Spear mint prefers loamy sandy soils or peaty soils rich in organic matter. Drainage is very important and hence clayey soils should be avoided.
Japanese mint- CIMAP / Hybrid-77 Pepper mint- EC.41911 is recommended, it has higher menthol content Spear mint-‘Kiran’
The field should have a good tilth, which can be obtained by thorough ploughing. It is propagated by suckers,runners or stolons. About 500 to 600kg of suckers are required per hectare. Though planting can be done form the end of December to March, second week of February is considered best for higher herbage yield. Delay in planting in reduction of herbage and oil yield.
Mentha being a shallow rooted plant, it is better to irrigated at frequent intervals.
Irrigation immediately after planting and harvesting is essential in case of pepper mint crop. Whereas for spear mint crop requires irrigation during summer or immediately after each cutting. It is also desirable to stop irrigation a weak prior to harvesting
Weeding is one of the important inter cultural operations since yield of oil depends largely on the extent of its freeness from weeds. Proper control of weed is essential for the successful growth of bergamot mint. Granular application of lasso @ 35kg/ha as a pre-emergence weedicide is recommended specifically for bergamot mint.
In case of Japanese mint first harvesting commences about 120 days from planting. On an average, 25-30 kg of oil can be obtained in the first year and 20-25kg in the second year. The right stage for harvest is very important to distill quality oil in pepper mint. Harvesting is generally done when the mint is in bloom stage to get optimum oil yield and menthol content. For spear mint the first cutting is taken during May to June and second harvesting is taken during August/September and third harvest during October/November. The oil recovery ranges from 0.02 to 0.06% depending upon many factors such as 75 to 150kg per year.
Opium poppy (Papaver somniferum L.)
It is an outstanding medicinal plant, the products of which viz opium and codeine are imporant medicines used for their analgesic and hypnotic effects.
It is a crop of temperate climate but can be grown successfully during winter in sub-tropical regions. Frosty or desicating temperature, cloudy or rainy weather leads to reduce not only the quantity but also the quality of opium. Opium poppy prefers a well-drained, highly fertile, light black or loam soil with an optimum pH around 7.0.
Telia, Dholia are some of the local races recommended for commercial cultivation.
The field should be ploughed 3 or 4 times to produce well pulverized soil. The field is then prepared into beds of convenient size.
The seed is either sown or broadcast in lines. Before sowing, the seeds may be treated with fungicides like Dithane M.45 @ 4g per kg of seeds. Seed rate is 7-8kg/ha for broadcast method and 4-5kg/ha for line sowing. A spacing of 30cm between lines and 30cm between plants is normal adopted.
Thinning is an important cultural practice to ensure uniform plant growth and better development. This is normally done when the plants are 5-6cm high, having 3-4 leaves.
Farm yard manures @20-30t/ha is generally applied by broadcasting while the field is prepared for sowing. Besides, 60-80kg of N and 40-50kg of P2O5 per hectare is recommended. No potash is applied. Half of N and entire P are applied at sowing time through placement and remaining half of N placed at rosette stage.
A light irrigation is given immediately after sowing followed by another light irrigation after 7 days when the seeds start germinating. Normally, 12-15 irrigations are given during the entire crop period.
The crop is left for drying for about 20-25days when the last lancing on the capsules stops exudation of latex. The capsules are then picked up and the plant is removed with sickles. Harvested capsules are dried in open yard and seeds are collected by beating with a wooden rod. The yield of raw opium varies from 50-60 kg/ha.
TOBACCO (N.tobacum, N.rustica)
India produces a wide range of commercial types of tobacco.
The nurseries for producing seedlings are located on sandy or sandy loams. Rabbing the nursery area is practiced in some places.
Digging with a spade, followed by ploughing with a mould-board plough and a country plough and then a harrowing, is recommended. Farmyard manure is usually applied and the dose varies from 10 to 12 cartloads per hectare for different types of tobacco. Application of phosphorus and potash was found beneficial for some tobaccos.
The distance between the rows and between the plants within a row varies with the type of tobacco. Based on the research findings, a spacing of 80cm x 80cm for natu and the flue-cured Virginia tobacco in black soils and 100cm x 60cm for the flue-cured Virginia tobacco in light soils.
The irrigation water should not contain more than 50 ppm of chlorides, as otherwise the leaves get burnt and other qualities suffer. In black soils also, in adverse conditions, one irrigation on 40-day-old plants is recommended.
Topping and suckering
The removal of the flower head alone or along with some of the top leaves of the plant is known as topping. It is done for imporving the size, body and quality of the leaves.
The leaves are considered ready for harvesting when the normal green colour changes to yellowish green or to light yellow. Harvesting starts from the bottom and each time 2 or 3 leaves are harvested. In another week, the next 2 or 3 leaves mature when they are harvested. Thus the 20-24 curable leaves, that become available per plant in the case of the flue-cured Virginia tobacco, are harvested in 6 to 8 primings at weekly intervals. Soon after harvesting, the leaves are strung on bamboo sticks at the rate of about 100 leaves per stick and loaded in the barn for curing. The bidi tobacco is harvested in January-February when the majority of the top leaves develop red rusty spots known as spangles. The cigar and cheroot tobaccos are harvest 90 to 100days after planting when the leaves pucker and become brittle and yellowish green. The chewing tobacco is harvested 110 to 120 days after planting when the leaves develop pronounced puckering. The hookah tobacco (rustica) is harvested in May or June. The whole plants are harvested in the case of the bidi, cigar and cheroot, chewing and hookah tobaccos.
Tobacco leaves are cured after harvesting in order to impart the required colour, texture and aroma to the final product. Different methods of curing are adopted for different types of tobacco, depending on its quality requirements and the use to which it is put to. Flue-curing, air-curing (or shade-curing), sun curing (or rack-curing or ground-curing), smoke-curing and pit curing are the different methods of curing. The Virginia tobacco is cured in special chambers, known as barns with artificial heat passing through metal pipes, called flues.