Ginger is a biennial or perennial reed-like herb, grown for the pungent, spicy underground stems or rhizomes. The stems reach a height of 3 feet, with lanceolate, smooth leaves up to 8 inches long. The plants are propagated by small divisions of the rhizomes.Ginger is a tropical plant adapted for cultivation even in regions of subtropical climate such as the high ranges. It prefers a rich soil with high humus content. Being an exhausting crop, ginger is not cultivated continuously in the same field but shifting cultivation is practised. The crop cannot withstand waterlogging and hence soils with good drainage are preferred for its cultivation. It is shade tolerant / loving crop with shallow roots and therefore suitable for intercropping and as a component in the homesteads where low to medium shade is available.
Ginger rhizomes are used for planting. For selection and preservation of seeds, adopt the following methods:
Mark healthy and disease free plants in the field when the crop is 6-8 months old and still green. Select best rhizomes free from pest and disease from the marked plants. Handle seed rhizomes carefully to avoid damage to buds. Soak the selected rhizomes for 30 minutes in a solution of mancozeb and malathion to give terminal concentration of 0.3% for the former and 0.1% for the latter. Dry the treated rhizomes in shade by spreading on the floor. Store the treated rhizomes in pits dug under shade, the floor of which is lined with sand or saw dust. It is advisable to spread layers of leaves of Glycosmis pentaphylla (panal). Cover the pits with coconut fronds.
Examine the stored rhizomes at monthly intervals and remove the rhizomes that show signs of rotting. This will help to keep the inoculum level low. Provide one or two holes for better aeration. Treat the seed rhizomes similarly before planting also.
Dry ginger: Maran, Wayanad, Manantoddy, Himachal, Valluvanad, Kuruppampady, IISR-Varada, IISR-Rejatha and IISR-Mahima
Green ginger: Rio-De-Janeiro, China, Wayanad Local and Tafengiya
Rio-De-Janeiro is preferable for extraction of oleoresin
Preparation of land
Clear the field during February-March and burn the weeds, stubbles, roots etc. in situ. Prepare the land by ploughing or digging. Prepare beds of convenient length (across the slope where the land is undulating), 1 m wide, 25 cm high with 40 cm spacing between the beds. Provide drainage channels, one for every 25 beds on flat lands.
Season and method of planting
The best time for planting ginger is during the first fortnight of April, after receipt of pre-monsoon showers. For irrigated ginger, the best-suited time for planting is middle of February (for vegetable ginger).
Plant rhizome bits of 15 g weight in small pits at a spacing of 20 x 20 cm to 25 x 25 cm and at a depth of 4-5 cm with at least one viable healthy bud facing upwards. Adopt a seed rate of 1500 kg/ha.
Immediately after planting, mulch the beds thickly with green leaves @ 15 t/ha. Repeat mulching with green leaves twice @ 7.5 t/ha first 44-60 days and second 90-120 days after planting. Grow green manure crops like daincha and sunn hemp in the interspaces of beds, along with ginger and harvest the green manure crop during second mulching of ginger beds.
Remove weeds by hand-weeding before each mulching. Repeat weeding according to weed growth during the fifth and sixth month after planting. Earth up the crop during the first mulching and avoid water stagnation.
1. For control of shoot borer spray dimethoate or quinalphos at 0.05%
2. For control of rhizome rot adopt the following measures:
a. Select sites having proper drainage.
b. Select seed rhizomes from disease free areas.
c. Treat seed rhizomes with 0.3% mancozeb.
d. When incidence of rhizome rot is noted in the field, dig out the affected plants and drench the beds with cheshunt compound or 1% Bordeaux mixture or 0.3% mancozeb.
e. Inoculation with native arbuscular mycorrhiza, Trichoderma and Pseudomonas fluorescens at the time of planting is recommended as a biocontrol measure.
3. For controlling the leaf spot disease, 1% Bordeaux mixture, 0.3% mancozeb or 0.2% thiram may be sprayed.
4. For control of nematode in endemic area, apply neem cake @ 1 t/ha at planting and carbofuran 1 kg ai/ha at 45 DAP.
Harvesting and processing
For vegetable ginger, the crop can be harvested from sixth month onwards. For dry ginger, harvest the crop between 245-260 days. After harvest, the fibrous roots attached to the rhizomes are trimmed off and soil is removed by washing. Rhizomes are soaked in water overnight and then cleaned. The skin is removed by scrapping with sharp bamboo splits or such other materials. Never use metallic substances since they will discolour the rhizomes. After scrapping, the rhizomes are sun-dried for a week with frequent turnings. They are again well rubbed by hand to remove any outer skin. This is the unbleached ginger of commerce. The peeled rhizomes are repeatedly immersed in lime solution (2%) and allowed to dry in the sun for 10 days while rhizomes receive a uniform coating of lime. This is the bleached ginger of commerce.
Ginger oil is prepared commercially by steam distillation of dried powdered ginger. The yield of oil varies from 1.3 to 3.0 per cent. The major use of ginger oil is as a flavouring agent for beverages, both alcoholic and non-alcoholic.
Oleoresin from ginger is obtained conventionally by extraction of dried powdered ginger with organic solvents like ethyl acetate, ethanol or acetone. Commercial dried ginger yields 3.5-10.0 per cent oleoresin. Ginger oleoresin is a dark brown viscous liquid responsible for the flavour and pungency of the spice.