AGRO TECHNIQUES

Climate and soil

Potato is basically a temperate crop. It is largely grown in regions where mean temperature does not exceed 18⁰C. In India , it is generally grown when maximum day temperature is below 35⁰C and night temperature not more than 20⁰C. Optimum temperature for potato growth ranges from 15 to 25⁰C. Temperature below 21⁰C favours tuberization. Long photo period favours haulm growth but delays tuberization and maturity. Whereas short photoperiod reduces haulm growth but tuber initiation is early and maturity period is reduced. Therefore, time of planting in potato assumes greater significance.

Potato is grown in all types of soils, but light, well-drained sandy loam soils are best-suited. In India, maximum area under potato is in alluvial soils, followed by hill, black and red soils. Potato prefers soils in acidic neutral range (pH 5.5 - 6.0).

Land preparation

Potato field must be properly labeled with proper surface drainage. Six or seven ploughing and planking are required to make the soil loose, friable and porous.

Seed

Certified seeds should be preferred, small seed potatoes sprouts late and in smaller numbers, while large seed tubers sprout earlier. Tubers should be true-to-type. Medium-sized, 40-50 g in weight, 40-45 mm in diameter and disease-free tubers should be preferred.

The seed rate varies according to sowing time. In general, 15-20 q large whole tubers, 10-15 q medium-sized tubers, 8-10 q small size tubers and 6-8 q cut tubers are required for 1 ha area.

Growing season

Planting in Northern plains is done from mid-September and can be extended to mid-January. However, second fortnight of October is optimum time for planting of main crop in Northern plains. In South India, 2 crops in rabi and kharif, whereas in Nilgiri hills 3 potato crops are raised in succession, i.e. April, August and January planting depending on the onset of rains.

Seasons for potato production in India

Sowing

It is sown either on ridges or in flat beds. Sowing on ridges gives higher yield. In Maharastra, Karnataka and some parts of Uttar Pradesh flat bed sowing is also done. Spacing between each row is kept 15-22 cm while the spacing for ridges may vary from 45-60 to 75 cm row-to-row and 15-22 cm from plant-to-plant according to variety and time of sowing.

Manures and fertilizers

Potato being a shallow-rooted crop, requires high nutrients. It needs 120-150 kg N, 45 kg P₂0₅ and 100 kg K₂O /Ha. The response to NPK depends not only upon the fertility status of soils but also on variety, cropping system and source of nutrients.

Interculture

Keep the soil loose and destroy weeds. The first earthing-up should be done when plants are 15-25 cm high. The second earthing-up is often required later to cover up the tubers properly.

Weed control

Weedicides like linuron or simazine (0.5 kg/ha) applied as pre-emergence spray are effective. Lasso @ 2 litres/ha can also be used.

SEED PLOT TECHNIQUE

This technique of seed production envisages raising a crop (using healthy seed) during the period when aphids (vectors of virus diseases) population is very low, taking precautions of use of insecticide and periodic rouging of diseased plants and finally dehaulming the crop before the aphids reach to the critical level of 20 aphids/100 compound leaves. The seed potatoes produced in the plains gives better plant stand and yield in all potato-growing regions because of its better physiological age for giving quick emergence and faster growth of haulms.

TRUE POTATO SEED (TPS)

Non-availability of quality seed tubers, high seed cost, virus infiltration in seed tubers causing degeneration of seed stocks and problems of long distance transport of seed from seed-producing areas have led to the development of true potato seed (TPS) technology of crop production. This technology envisages the use of botanical seed or TPS for crop production. It has gained significance because unlike seed tubers, TPS can be produced in all parts of the country providing extra light for 4-5 hours depending upon climatic condition. It can be easily stored over long periods of time. Disease transmission by TPS is negligible and it provides cheap planting material. About 100-120 g TPS is enough to raise a seedling crop for one hectare or if the commercial crop is to be produced using seedling tubers, the produce of 40-45 g TPS is enough to plant one hectare crop next year. They also provide better disease resistance because of high heterogeneity in the population.

PHYSIOLOGICAL DISORDERS

Non-parasitic diseases which are the result of physiological imbalance caused by unfavourable environmental conditions are mentioned as below.

Internal Brown Spot

It is characterized by irregular, dry brown spots scattered through the flesh of tubers. These spots are never found in vascular regions as in case of brown rot. It is a very minor disorder that appears particularly in light sandy soils which are not irrigated regularly.

Black heart

If potato tubers are stored in air at a temperature of 35-45⁰C they develop a condition known as black heart in a few days, in which inner tissues break down and become black. Lack of oxygen is the probable cause. It is also probable that at high storage temperature, accumulation of CO₂ at the centre of tubers might contribute to damage and subsequent decrease in respiration and development of black heart. Therefore avoid storage temperature above 35⁰C and poor ventilation.

Hollow heart

Hollow heart consists of an irregular cavity in the centre of tubers. In tissues surrounding the cavity, there is no decay or discolouration. Hollow heart condition appears often in varieties which produce over-sized tubers. In extra large-sized tubers of Kufri Jyoti and Kufri Sindhuri, hollow heart may appear which can be avoided by closer spacing plants and avoiding excessive use of fertilizers.

Chilling injury

Chilling injury may follow prolonged storage of tubers at temperature above 0⁰C. This results in discoloured blotches in flesh of tubers which vary from light reddish-brown to dark brown, diffuse brownish-black patches on skin and reduce or completely inhibit sprouting of affected tubers when planted.

Freezing injury occurs as a result of ice formation in potato tubers when exposed to temperatures between 1⁰C and 2⁰C.

HARVESTING AND POST-HARVEST MANAGEMENT