Botanical name: Solanum tuberosum
family : Solanaceae
Potatoes are few of the tuber-bearing plants belonging to this family. The potato plants are annuals attaining a height of maximum 2 feet. They propagate through underground tubers. The buds on the tubers develop into leaves and stems. The flowers maybe pink, red, white, purple or blue flowers bearing yellow stamens. The fruits borne by the plant after flowering are small and green in color. They resemble cherry tomatoes. Each fruit has at least 300 seeds in them. Tubers are the only edible part of this plant since other plant parts contain the alkaloid toxin called solanine. Hence except tubers, no other plant part is suitable for consumption.
Climate for Potato Cultivation
Being a cool season crop, the best place for potato farming are places with a cool climate, fertile soil and good moisture. Temperature, light, soil type, moisture content and nutrients influence the growth of potatoes in a great way. Tubers stop developing at a temperature above 30⁰C. This is because, as the temperature increases, the rate of respiration increases. In the process, carbohydrates produced through photosynthesis get consumed instead of getting stored in the tubers. Thus, tuber formation gets affected at higher temperature. Soil temperature of 17-19⁰C is ideal for potato tuber formation. Bright sunshine during day and cool nights are optimal for potato growing.
Soil for Potato Cultivation
Potato tubers require ample amount of air and water. In addition they need space underground to expand and swell in size as they grow. Therefore, a loose, loamy soil is optimal. Clayey soil keeps the water and air from reaching the roots. In addition, since they stick a lot the tuber growth gets restricted.Soil pH must be maintained between 4.8 and 5.4. It is on a slightly acidic side to promote carbohydrate formation and storage in tubers.
There are many varieties of potatoes either introduced into or bred in India some of the important newly improved varieties are described below.
Medium maturing (31/2 to 41/2 months) with round, light red medium-sized tubers. It is suitable for cultivation as a main crop variety in plains as a replacement to Kufri Red and other later varieties.
Early maturing (mature 10 days earlier than upto-date), with attractive, oval, white tubers. It degenerates so slowly and keeps well in storage. It gives high yields and cooks easily and does not degenerate rapidly in the plains.
An early maturing variety, possessing a good degree of field resistance to late blight and moderate resistance to early blight and viruses, fit for growing in the hilly regions of Assam.
An early bulking variety with uniform-sized, shining and smoothed tubers.
A front-resistant variety, suitable especially for the Punjab, Rajasthan, Haryana and U.P. It can be planted late in the northern plains due to its high degree of resistance frost.
A widely adaptable, fertilizer-resistant variety possessing a high degree of field resistance to late blight disease in the foliage and also a good degree of tuber resistance to the same disease. This variety is also resistant to the wary disease and moderately resistant to cercospora leaf blotch.
Sowing time for Potato Cultivation
Being a rabi season crop, it is usually cultivated during the months from October to December. This is the time when the weather is neither hot nor cold. Since the monsoons are nearly over at this time, it is an ideal time for cultivating potato crop.
Slightly acidic, loose soil is optimum for potatoes. Therefore, the land must be ploughed well 2-3 times and then harrowed. This ensures good tilth and clod-free seedbed. All the hard pans and rocks must be destroyed during the land preparation stage. Presence of hard pan can interfere with water and air circulation for the tubers which would in turn affect the potato growth. The beds must be prepared keeping a distance of 60-90 cm between the beds and the intra-bed distance must be about 45 cm.
Irrigation for Potato Farming
For potato, the daily crop water requirement is 4-5mm a day. For a better yield, irrigation must be done immediately after sowing. This allows for proper seed germination. The irrigation frequency varies with the place. For example, it is irrigated once a week in Punjab since the tuberization period coincides with the cool weather and thus low evaporative rate in the place. On an average, they need 4-5 mm water per day- just enough to maintain the moisture level, temperature and thus promote uniform tuber formation. The last lot of irrigation is done about fifteen days prior to harvesting. This promotes hardening of tuber skin before harvesting potatoes.
Application of Manures and Fertilizer
F.Y.M. 250-400 g/hectare
80-120 kg/hectare (P)
80-120 kg/hectare (K)
To be incorporated into the soil 3 to 4 weeks before planting half dose of nitrogen full dose of P2O5 and K2O as basal dressing at planting and remaining nitrogen dose is given at the time of earthing up.
While planting, the soil temperature must not be beyond 16⁰C and the planting depth must be 5 to 10cm. There are two very important points that must be considered while planting.
The seed material must be procured from reliable sources. It is advisable to approach the local government agricultural body for this purpose. The tubers must be well-sprouted and must weigh about 50-60g in size. The seeds must be treated with 0.3% mancozeb before sowing. This is to avoid soil and tuber borne diseases.
Potato Planting Time
This is another important factor in case of potato cultivation. The planting time for potato is different for different parts of India.
In the central plains of India such as Madhya Pradesh, Gujarat and Orissa, potato is a winter or rabi crop. Therefore, the time of planting here is during the months of October and November.
Potato can be both kharif and rabi crop in the Deccan plateau, i.e., in states like Andhra Pradesh, Karnataka and Maharashtra. In other words, two crops of potatoes can be grown in these regions- from mid-June to mid-July and then during October and November.
In the southern plains, potatoes are grown throughout the year during summer, autumn and spring. In other words, they are cultivated during April/May, August/September and January.
Weed Management in Potato Cultivation
For a good harvest, weed management is critical. Weeds compete with the plants for water, light and nutrient thereby affecting the tuber development and yield. The initial 4-6 weeks are the critical weed management period. Soil solarization, efficient crop rotation, maintaining optimum plant population, inter-cultivation, manual weeding and applying herbicides at appropriate intervals are some of the measures followed. Some of the herbicides recommended are metribuzin and alachlor in the pre-emergence period and parguat and propanil in the post-emergence period.
Diseases and Plant Protection in Potato Farming
Nature of Damage
This disease sets in once the foliage has developed fairly well. The diseased tubers decay before harvest.
- Infection begins at the lower leaves with presence of water-soaked lesions towards margins
- The lesions enlarge in case of favorable humidity and temperature
- Whitish cottony growth can be observed on the lower side of the leaves in humid places.
- Infected leaves begin to rot and turn black in color.
- Infected decaying leaves emit pungent odor.
- Stems also begin rotting
- Infected tubers exhibit greenish sunken areas.
- The seed tubers used for cultivation must be chosen from disease-free areas.
- The infected plant must be destroyed as soon as it is detected.
- Resistant varieties like Kufri Navtal can help control the disease.
- Spraying fungicides are effective if they are used in time. Dithane M-45 or Z-78 must be used for spraying and it must be repeated every 10 days.
Nature of Damage
This is a more common disease affecting the potato crop. It can occur at any stage of growth in potato farming.
- Leaves develop spots in the concentric rings ranging in color from brown to black.
- The spots are scattered all over the leaves.
- Infected leaves fall off and the infection spreads to stems.
Burning the crop debris after harvest is the most effective way of controlling the disease. But, this method cause air pollution.
Nature of Damage
This disease occurs in two phases and cause cankers leading to wilting of potato plants.
- Delayed germination since the sprouts get killed even before they emerge. This phase is called stem canker phase.
- Tubers have a black crust on them that makes them unacceptable in the market.
- Healthy, clear tubers must be chosen for potato planting.
- Dipping the seed tuber in Agallol (0.5%) for 10 minutes before sowing would help check the disease.
- Treat the soil with 10-12 Kg Brassicol per acre is another preventive measure.
- Pre-treatment of soil and seeds is the best way to control the disease.
Nature of Damage
This is a type of bacterial wilt caused by the Pseudomonas solanacearum which is a soil bacterium. It is most common in plateau regions and in West Bengal.
- Sudden, unexplained wilting of the plant is the most common symptom.
- The affected plants droop down while the affected branches turn brown.
- Eyes of the tubers blacken.
- Seed free, certified seeds must be used for potato planting.
- While using tubers for sowing, they must be stored at 12⁰C for 4-5 days so that the cut surfaces harden.
- Treat the tubers with Agallol solution before sowing.
- After harvest, the crop debris must be burnt.
Nature of Damage
This disease is prevalent in Darjeeling and surrounding hills. In severe cases, the tubers get converted to clumps of distorted mass.
Warts and tumors appear on the stems and tubers of the potato plant.
Since the disease is prevalent in the hills and north eastern areas, immune varieties are available which must be planted. At the time of planting, care must be taken to avoid wart affected tubers.
Nature of Damage
Plants affected by mosaic disease remain stunted in growth. The tuber size is also affected by the virus.
- Dark green and green mosaic pattern on leaves
- Some leaves show yellow patterns
- Disease spreads from sick to healthy plants through insects.
The tubers for sowing must be healthy and certified. The field must be monitored constantly and any plant showing the symptoms must be immediately destroyed. Spraying the crop with Rogor (280 mL dissolved in 250 litres of water per acre) every 15 days would also keep the viral infection at bay.
Potato Leafroll Virus
Nature of Damage
As the name suggests, the leaves of the plant roll from the margins to the mid-rib. The tuber size gets reduced greatly. This disease is very common in the plains.
- Leaves roll towards the mid-rib till the entire lamina is involved.
- Leaves have a leathery texture and produce a rattling sound when touched.
The control measures for both leaf roll and mosaic disease is the same.
- Cut worms – Spray Dursban 20 EC or apply Phorate in soil.
- Caterpillar – Spray Thiodan or BHC (10%)
- Aphid — Spray Rogor or Nuvacron or Malathion
- Jassids — Spray Metasystox (0.1%)
Harvesting of Potato
The harvesting time of potato is usually dependent on the weather and market prospects. In case of high demand in the market, harvesting is done slightly early. Irrigation of the plants is stopped at least a week before harvesting potatoes. Harvesting is done once the soil is completely dry. Some farmers kill the vines using Gramoxone Extra. This ensures a good skin set for the tubers. The treatment is done a week before harvesting. In order to avoid bruising or any other damage to the tubers, they are carefully dug using potato digger manually. There is no universal time for harvesting potatoes.
Potato is harvested from the time it is sufficient size until the vines are fully ripe. The average yield varies from 20 to 30 tonnes per hectare. The best method storing potato is in cold stores at 2.20 C to 3.30 C and at 75 to 80% relative humidity.