Cultivation
Planting
Potato enjoys a wide range of seasonal
adaptability. In north-western Himalayas, it is planted in May/June in valleys
and at very high altitudes (3,000–3,500m), during April in high hills
(2,500–3,000m), and as spring crop during January/February and as autumn crop
in August/September in the midhills (1,000–1,800m). In north-eastern hills ,
potato is planted in March in the high hills. In valleys and lower hills, there
are 2 potato-growing seasons with plantings in January/February and
August/September. In Nilgiri hills, 3 potato crops are raised almost in
succession, their planting times being April, August and January.
In Punjab and western Uttar Pradesh, early potato
crop is planted during 10–20 September, in central Uttar Pradesh in the first
week of October and in Bihar between second and third weeks of October. The
crop is usually harvested after 60–70 days to take advantage of high prices of
fresh potatoes. Mulching of early potato crop with paddy straw, paddy husk and
maize, and dhaincha stalks is beneficial for getting high yields. The
main crop in Gangetic plains is planted during October–November. The potato
season first starts in north-western plains and culminates in the eastern part.
Planting of late or spring crop in December/January is confined to the
north-western plains only. In plateau regions of peninsular India, where summer
temperatures are somewhat mild, 2 crops, one in winter and the other in
summer are raised.
For hot weather cultivation, the fields
are ploughed during summer in May and June to reduce the incidence of
soil-borne diseases and control perennial weeds. Green manure crops like dhaincha
and sanali may be sown before the onset of the monsoon. The green manure
crop is buried in soil after 7–8 weeks. This practice reduces N, P and K
requirement of the crop by 20–30% and improves potato yields up to 3 tonnes/ha.
If green manuring of the fields is not possible,
farmyard manure @ 15–20 tonnes/ha may be incorporated and ploughed in field
before planting. After deep ploughing and good pulverization of the soil, when
the seed bed is ready, tubers are planted in lines. The first line is drawn
straight with a rope and subsequent lines are marked at a distance of 60cm from
row-to-row with help of a marker. Half dose of N and full dose of P2O5
and K2O is applied in furrows and mixed in soil. Seeds are kept in
the furrows at a distance of 20cm, from tuber-to-tuber and covered with soil
using a ridger. The planting should preferably be done in the morning or in the
evening to avoid heated up soil covering during mid-day in plains.
Manuring and fertilization
Nitrogen is most important nutrient for potato
crop. A mature potato crop yielding between 25 and 35 tonnes/ha need to about
120–150kg N/ha. The peak period of N uptake varies from 40–70 days in plains
and 65–85 days in hills. Nitrogen application increases the plant growth, leaf
area, tuber number and tuber size. The maximum N response is recorded in
alluvial soils followed by hill soils, red soils and black soils. Potato varieties
differ among themselves in their N fertilizer needs. The long-duration
varieties are more responsive to N fertilizers than the short-duration ones.
The N is applied in split doses. Half of the dose should be applied at the time
of planting and the remaining half at the time of earthing-up.
The P is the second limiting nutrient in potato
production. Its deficiency is more pronounced in acidic hill soils and red
laterite soils. An average crop yielding 25 tonnes/ha needs about 45kg P2O5.
Phosphorus deficiency, retards growth, and leaves become dull dark green
without lustre. The application of 50–100kg P2O5/ha along
with N is required in most of the soils. Full dose of P is applied at the time
of planting.
The application of K along with N and P is needed
to get optimum yield. Its deficiency retards plant growth and shortens
internodes. Leaves become dark bluish green in mild K deficiency, terminal
leaves show bronzing accompanied with necrotic spots. On an average, potato
plant removes 150kg K/ha from alluvial soils of the plains and 190kg K/ha from
acidic brown hill soils. Response to K is highest in alluvial soils, followed
by hill soils, red soils and black cotton soils. The optimum K dose is 98 kg/ha
for alluvial soils, 93 kg/ha for hill soils, 111 kg for red soils and 70 kg/ha
for black soils.
The response to N,P and K depends not only upon
the fertility status of the soils but also on variety, cropping system and
source of nutrients. The P and K applied to soil leave significant residues
which affect the fertilizer needs of the succeeding crop.
The potato crop in most parts of the country
generally does not respond to the application of Zn, Cu, Mg and Fe. Only
marginal increase in yield of potato has been observed with application of Zn
at Kalyani (West Bengal), Kanpur (Uttar Pradesh) and Palampur (Himachal
Pradesh); with Fe at Kanpur and with S (given through gypsum or pyrites) at
Hisar (Haryana), Faizabad (Uttar Pradesh) and Deesa (Gujarat).
Interculture
Earthing-up and weeding of potato are done as soon
as weeds emerge, but preferably when potato plants are about 8–10cm high. The
final earthing-up in plains is done 25–30 days after planting and in hills when
the crop is about 6–8 weeks old. Second half dose of N is applied at the time
of final earthing-up.
Irrigation
Water forms nearly 80% of the potato tuber.
Adequate and regular water supply is, therefore, needed for its sustained
growth. The crop in high hills and in plateau region in kharif season is
grown as rainfed, whereas in plains it is grown under irrigated conditions. The
quality of water used for irrigation is an important factor. Water with
high concentration of dissolved salts is undesirable for potato. First
irrigation immediately after planting, particularly if soil is relatively dry,
is desirable for better emergence. Second irrigation may be given after 12–15
days when 2–5% germination has taken place. Subsequent irrigations may be given
at 6–10 days intervals depending upon soil and water demand. Water stress
reduces tuber yield and increases the proportion of small-sized tubers.
Mulching helps in getting higher yields in warmer regions of the country.
Harvesting and
Postharvest management
Potato tubers are harvested as soon as they
mature. In loam or heavy loam soils, tubers should not be allowed to remain in
wet soil after maturity because the lenticels on their surface may proliferate
and impart unacceptable look to the tubers. If harvesting is delayed, it is
best to leave the soil dry and irrigate the field lightly about the time of harvest.
It is never advisable to harvest the tubers in wet land. The late-sown crop in
plains should be harvested latest by April-end to avoid high temperatures and
charcoal-rot infection in tubers.
After harvesting, tubers should be surface-dried
and kept in shade in heaps for 10–15 days. All rotted and damaged tubers should
be periodically removed. The produce should be graded on the basis of tuber
size and packed in gunny bags for marketing.
If the produce is to be marketed early to take
advantage of high market price, it is advisable to harvest potatoes in stages.
This is because of highly perishable nature of the immature tuber. Fresh potato
has a delicate skin, which gets bruised easily and extensively providing
invasion site to rot-causing organisms. Also, bruising initiates oxidization
process, which subsequently imparts dark colour to the exposed surface of
tubers reducing its market value.
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