Introduction
Ajowan (Trachyspermum ammi) of the Apiaceae family, is native to India. It is grown on a large scale in Rajasthan, Gujarat, and Andhra Pradesh, and on a smaller area in Telangana, Uttar Pradesh, Bihar, Madhya Pradesh, Punjab, Tamil Nadu, West Bengal, and Karnataka. India is the leading ajowan-producer and exporter in the world. During 2013-14, 26,410 tonnes of ajowan seed was produced from 39,260 ha. The seeds (botanically a fruit) are largely used as condiments in the form of an ingredient in all mixed spices and in curry powder for flavoring vegetables, pickles, soups, sausages, cheese, and other culinary preparations, and for seasoning of bread, cakes and biscuits. Traditionally, the seed is used as a spice and also as a folk remedy for indigestion, intestinal gas, arthritis, asthma, coughs, and diarrhea. It is also valued for its antispasmodic and antiseptic properties.
Table of contents (toc)
Climate and soil
Ajowan is primarily a crop of arid and semi-arid agro-ecosystem and requires a warm and long frost-free growing season for successful cultivation. It is cultivated extensively as a cool-season crop in plains in the rabi season. In India, it is grown both under irrigated and rainfed cultivation systems. The crop has moderate tolerance to drought and is thus suitable for cultivation as a rainfed crop during the Kharif season in heavy soils. The crop cannot withstand waterlogging conditions. It needs a temperature between 15-27°C with a relative humidity of 65% during its growth period and requires preferably warm weather during seed development. It can be grown on almost all types of soils ranging from loamy to sandy loam and even in black soils, but a well-drained sandy loam soil having 7.5-8.0 pH is favorable for this crop.
Varieties
BEN 1 and BEN 2: Mature in 135 days and recommended for cultivation in Karnataka.
GA 1: Produces 25% more yield than the local type of Gujarat. Suitable for cultivation in Gujarat and Rajasthan. Matures in 175-180 days.
Lam Selection 1: Plants medium tall, mature in 135 days with an average yield of 800 kg per hectare.
Lam Selection 2: Plants bushy type, produce 40-45 branches per plant and produce an average yield of 1,000 kg per hectare in 135-140 days. Recommended for cultivation in Andhra Pradesh.
NRCSS AA 1: A late variety that takes about 165 days to maturity, possesses high yield potential with an average yield of about 1420 kg per hectare under irrigated conditions. The seeds yield essential oil content of 3.4%. This variety is recommended for cultivation in Rajasthan and Gujarat.
NRCSS AA 2: An early variety that matures in 147 days. An average yield of about 1280 kg per hectare under irrigated conditions and 520 kg per hectare under rainfed conditions. Possesses resistance to powdery mildew. Seeds yield essential oil content of about 3-3.5%. Recommended for cultivation in Rajasthan and Gujarat under rainfed conditions.
RA 1-80: A late maturing variety from Bihar, matures: in about 140-160 days. Seeds are small and aromatic. RA 19-80: Plants 135-140 cm tall, produce 30-40 branches and 180-200 umbels per plant. Mature in 125-130 days. Seeds of large size but less aromatic than RA 1-80.
Pant Ruchika: Matures in 135-140 days and recommended for cultivation in Uttar Pradesh and plains of Uttarakhand.
Cultivation
It is propagated through the direct sowing of seeds. The recommended seed rate is 2.5 kg/ha for irrigated and 4 kg/ha for rainfed conditions. An early crop of ajowan is mostly grown as rainfed which is sown during July August for the Kharif crop, whereas sowing for the main season crop (rabi season) is done during September-October.
Ajowan seeds are generally sown by broadcasting but sowing in lines in rows 45 cm apart under irrigated conditions and 30 cm under rainfed production system, facilitates better intercultural operations and aftercare. The plant-to-plant spacing should be maintained to 25-30 cm. Ajowan seeds are small in size thus the depth of seed should be kept between 1.0 and 1.5 cm in the soil for getting good germination. It is better to maintain the uniform spread of seed through mixing of seed with dry sand before sowing. The seed should be treated with Captan or Thiram (2.5 g/kg seed) before sowing. It takes 10-12 days for germination of ajowan seeds after sowing under optimum soil moisture conditions.
Nutrition
For raising a good crop of ajowan, apply 10 tonnes of well-decomposed farmyard manure or 5 tonnes of compost per hectare should be added in the soil 20-25 days before sowing and mixed properly through cultivators during field preparation. At the time of the last ploughing, add 40 kg N, 20 kg P₂O, and 20 kg K₂O/ha, whereas for irrigated crop and light soils, an additional dose of 40 kg nitrogen be given in two equal splits one at 45 days after sowing and second before flowering for the irrigated crop.
Irrigation
At the time of sowing, the soil must have sufficient moisture. If the field is deficient in moisture, pre-sowing irrigation is essential for better germination of seeds. It is cultivated both as a rainfed and irrigated crop. During most of the period of crop growth, the soil moisture should be maintained near optimum, hence, irrigations should be scheduled accordingly. However, irrigation at short intervals is beneficial in sandy soils and dry areas where cultivation of ajowan without irrigation is not feasible. Light irrigation at the flowering and seed setting stage is of greater significance. For rabi crops, irrigation must also be applied, if there is the danger of frost occurrence, which adversely affects mostly at flowering stage. Drip irrigation besides giving a saving of 25-30% water results in a 20% higher yield as compared to surface irrigation.
Aftercare
Initial growth of the ajowan crop is very slow, it is, therefore, necessary to keep the field free from weeds. Two to three weedings and hoeings are required. The first weeding should be done after 30 days of sowing accompanied by thinning from rows after maintaining suggested intra-row spacing. The subsequent wedding is done at 30-day intervals as per requirement. Weeds can also be controlled by spraying pendimethalin @ 1 kg a.i./ha after sowing. Care must be taken that there is sufficient moisture in the soil at the time of application of weedicide.
Organic farming
The ajowan seeds produced from India are mostly from arid and semi-arid regions, which are by default organic as crops are raised with minimal or no chemical inputs. Such products are sold in the market with the tag of near organic.
Diseases and pests
Diseases, as well as insects, do not pose many problems in raising an ajowan crop. However, the incidence of powdery mildew and aphids may appear occasionally.
Harvesting and post-harvest management
The crop matures in 120-180 days depending upon the variety and season. The harvesting is usually done from February to May. At maturity, flowering closes, and the seed becomes brown in umbles. An average yield of 400-600 kg/ha under rainfed farming and 1,200-1,500 kg/ha under irrigated conditions can be obtained. The harvested ajowan crop is dried hygienically in a thin layer on a clean threshing floor for 1 or 2 days before threshing of seeds. Seed dried in shade has a greater oil content than the sun-dried seed. The drying of ajowan seed is often carried out in zero energy solar drier polytunnels to avoid entry of dust and foreign matter. The seed is cleaned in a screening mill and then processed through a gravity separator. Seeds that have been well dried at the level of 8-9% seed moisture, cleaned, and graded by sieving are stored in polyethylene-lined gunny bags in a cool dry place.
Value-addition
The finer powder product from ajowan seeds is mostly used for the seasoning of foods, whereas the coarse product is used for the purpose of extraction of oil, oleoresin, and other extractives. Ajowan powder is produced by grinding dried seeds through cold milling or cryo-grinding without much loss to volatile compounds. It is better to use fresh seeds for more recovery of quality essential oil. Both essential oil (volatile oil) and non-volatile fatty oils can be extracted. The mature dried seeds are distilled through hydro or steam distillation methods for the extraction of essential oil. However, oil of the highest quality can be obtained by using the supercritical fluid extraction method.
On average, the dry seeds yield 2-4% oil and about 26% of fatty oils. Ajowan oleoresin is prepared by extraction of crushed dried seeds with suitable volatile oil solvents. The ajowan essential oil is also used in the preparation of lotions and ointments in the cosmetic industry. The characteristic flavor of ajowan oil is due to the high content of thymol, which can also be crystallized from oil (ajowain ka-Phool or sat ajowain) for use in the medicinal industry as an ingredient for deodorant, mouthwashes, toothpaste, and many indigenous pharmaceutical preparations.
