MEDICINAL AND AROMATIC CROPS (2+1)

Cultivation

Seasons

In the plains, planting is done during the winter months, whereas in temperate climates, planting is done in autumn or spring from the last week of December to the first week of March or from the first week of January to the third week of February. Late planting always gives poor yields.


Soil

Medium to fertile deep soil, rich in humus is ideal for the cultivation of mint. The soil should have a good water-holding capacity but water-logging should be avoided. A pH range of 6-7.5 is best.


Climate

Japanese mint can be grown in all tropical and subtropical areas under irrigation. However, it does not tolerate damp winters which cause root-rot. A temperature of 20-25°C promotes vegetative growth, but the essential oil and menthol are reported to increase at a higher temperature of 30°C under Indian conditions. Peppermint and spearmint cannot be grown profitably in tropical and subtropical areas, especially those areas with very high summer temperatures (41°C) and the ideal yield is obtained only in humid and temperate conditions like in Kashmir and the hills of Uttar Pradesh and Himachal Pradesh. Open, sunny situations without excessive rains during the growing period are congenial for the good growth and development of the oil.


Bergamot mint can be grown both in temperate as well as sub¬tropical areas. However, the yield is higher in temperate climates.


Land preparation

Mints require thoroughly ploughed, harrowed, fine soil. All the stubble of weeds should be removed before the crop is planted. Manuring may be done at the time of land preparation by adding FYM @ 25 to 30 t/ha. Green manuring may also be done before the mint is planted. Sun-hemp (Crotalaria juncea L.) is an ideal green manure crop. Mints are planted on flat land or ridges. Hence, flat beds of convenient sizes or ridges are made according to the spacing recommended.


Propagation

Mints are propagated through the creeping stolons or suckers. In the case of peppermint and bergamot mint, even runners are planted. Stolons are obtained from the previous years planting. A hectare of well-established mint, on an average, provides enough planting material for ten hectares. About 400 kg stolons are required for plant¬ing one hectare of land. The best time for obtaining stolons is during the months of December and January.


Planting

The stolons are cut into small pieces (7-10 cm) and planted in shallow furrows about 7-10 cm deep with a row-to-row distance of 45-60 cm, manually or mechanically. While planting on ridges, the stolons are planted half-way down on the inner sides of the ridges. The plot is irrigated immediately after planting.


Fertilizer application

Mint responds very well to a heavy application of nitrogenous fertiliz¬ers. The increase in herbage by the application of phosphorus is not as remarkable as in case of nitrogen. Generally, nitrogenous fertilizers @ 80-120 kg; P and K at 50 kg are required for a good crop of mint. However, in M. arvensis an increase of up to 160 kg N/ha and, in M. piperita, 125 kg N/ha has given increased fresh herbage and essential oil-yield. Potassium application has no significant effect on herb and oil-yield. In M. spicata, the maximum herb-yield is obtained with the application of 100-120 kg N/ha. Nitrogen may be applied in three split doses at 1 and 3 months after planting and the third dose after the first harvest of the crop. Boron deficiency reduces both the yield of green herb and the essential oil in peppermint. Increased yields of herb, menthol content and essential oil content in peppermint have been obtained by using a combination of boron and zinc fertilizers.


Irrigation

The water requirement of mint is very high. Depending upon the soil and climatic conditions, the crop is irrigated 6-9 times before the first monsoon. The crop requires three irrigations after the monsoons during September, October and November. Sometimes irrigation is required during winter, if the plant is dormant and there are no winter rains to encourage proper growth of the under¬ground stems.


Intercultural and weed control

Uninterrupted weed growth causes about 60% reduction in herb and oil-yields. Hence, mints require weeding and hoeing at regular inter¬vals in the early stages of crop growth. One hand-weeding is required after the first harvest. Combining organic mulch with a combi¬nation of 0.5 kg/ha of Oxyfluorfen herbicide and weeding give excellent weed control throughout the crop growth.

In low temperature areas, the plant becomes dormant in Novem¬ber. In order to give a perennial crop (of 3 years only) in peppermint, replanting is done either in autumn (November-December) or in spring (March-April).


Crop rotation

The following crop rotations are in practice in Uttar Pradesh (a) Mint-maize-potato (b) Mint early paddy and potato and (c) Mint-late paddy and sweet pea. Whereas, in Punjab, the farmers practice mint-maize and rape seed/mustard and mint-maize and 'potato or mint and paddy rotation. The recommendation for the Terai region of Uttar Pradesh is a 2-year rotation of mint-summer fallowing or millet (fodder) followed by mint on poor fertility lands and mint-wheat-paddy and mint on medium-fertile lands.