Seed Plot Technique in Potato
Introduction:
Botanical name: Solanum tuberosum
Chromosome no: 2n = 12
Family: Solanaceae
Origin: South American state Peru/Chilly
Land Requirements
A crop of seed potato shall not be eligible for certification if grown on land infested with wart and/or cyst forming nematodes; or brown rot or Non cyst forming nematodes within the previous three years; and common scab. The soil of the selected field should be well-drained, well-aerated, deep, and having a pH range of 5.2 to 6.4.
Isolation Requirements
A minimum isolation distance of five meters for foundation and certified seed class should be provided all around a seed field to separate it from fields of other varieties, and fields of the same variety not conforming to varietal purity and health requirements for certification.
Brief Cultural Practices
1. Time of sowing: The sowing should be done from 20th September (when rainfall is low), or 25th September, up to 15th October.
2. Seed rate: Seed rate depends upon tuber size. 25 to 30 qt./ha of seed potato will be sufficient if the usual sized tuber (4 to 6 cm) is used.
3. Source of seed: Obtain nucleus/foundation seed from source approved by a certification agency.
4. Preparation of field: Prepare the field to good tilth by deep ploughing, three to four harrowing, followed by levelling.
5. Fertilization: Need 100 to 125 kg nitrogen, 80 to 100 kg phosphorus and 80 to 100 kg potash per hectare. Farmyard manure may be added at the rate of 25 Tonnes per hectare if soil is poor in organic matter. A leguminous crop before potatoes may also partially replace organic matter requirement. Apply all phosphorus, potash, and half of the nitrogen at the time of sowing. The remaining half of nitrogen should be applied about thirty-five days after sowing, or when the plants are about 25 to 30 cm high. For the best results, the fertilizers should be placed either 5 cm below the tubers, or on the side.
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| Seed Plot Technique in Potato |
6. Method of sowing. Whole tubers should be used for planting. Tubers should be under sprouting (sprouts 0.5 to 1 cm long) for quick emergence. Care must be taken that each piece to be used for planting has two or three emerging eyes and weighs at least 40 gm. Plant the tubers 3 to 4 cm deep in the soil having adequate moisture. At planting, tubers should not come into direct contact with fertilizers which should be placed right below the seed potato.
Row to row spacing at 60 cm and tuber to tuber spacing at 15 to 20 cm is recommended.
7. Irrigation: Potatoes require light and frequent irrigation. First irrigation should follow immediately after emergence. Subsequent irrigations should be done at proper intervals. The top of the ridges should not be submerged. Restrict the irrigation after the crop has tuberised well. Withhold irrigation by the third week of December i.e., ten to fifteen days before cutting of haulms.
8. Interculture: Keep the field free from weeds. At least one earthing-up is necessary. It should be done when plants attain the height of 15 cm. Exposed tubers should be covered with soil during subsequent earthing-up.
9. Haulm cutting. The practice of haulm cutting is adopted as a precautionary measure to avoid chances of viral disease transmission through vectors like aphids. The haulms must be cut by the end of December, or at the latest by the first week of January before the aphid population reaches the critical stage (20 aphids per hundred compound leaves). No regrowth should be allowed.
Roguing
Very careful roguing is required for producing a high-quality crop of seed potato. The roguing is to be done at the following stages.
First roguing; First roguing should be done twenty-five days after sowing to remove:
(a) All virus-affected plants, and (b) All plants apparently belonging to other varieties, which can be identified from foliage.
Second roguing: It should be done when the crop is fully grown. This would be about fifty to sixty days after sowing. At this time tubers are formed and, therefore, while roguing, not only the upper portion of plant, but all the tubers belonging to the plant should be removed carefully. Also, at this stage the virus-affected plant as well as off-type, if any, should be removed.
Third roguing: This is the third and final roguing and should be done just before cutting the foliage. Foliage should not be cut unless this roguing has been completed. At this stage, all virus-affected plants, and off-type plants, if any, along with their tubers must be very carefully removed, so that no such plants are left in the fields.
Harvesting:
(a) Time of harvest: The crop is ready for harvest ten to fifteen days after haulm cutting when the skin of tuber has hardened. Premature harvesting causes handling problems, as the soft skin gets easily peeled off and, further, such tubers cannot withstand long transportation and storage.
Also read - Quality Seed Production of Carrot
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| Seed Plot Technique in Potato |
[Reference : Rattan Lal Agrawal ]
(b) Soil conditions at the time of harvest: At the time of potato digging, the moisture in soil should be optimum for obtaining clean tubers.
(c) Method of harvest and curing: The harvesting of seed potatoes can be done by any of the equipment available in the market for this purpose. Every effort should be made to avoid cuts, bruises, etc. After harvesting, tubers should not be left exposed to the hot sun for a prolonged period (not more than an hour). It should be immediately lifted and carried to an airy shed and kept in piles (height one meter, width three meters) for seven to ten days so that the superficial moisture evaporates, and further hardening of skin is achieved. If sheds are not available, piles may be made in field and covered with dry haulms.
Sorting and Grading:
When the potatoes are properly cured, grading should be done. A single grade from 3.0 to 5.5 cm is being made at present for "Plain Seed" by hand grading. While grading, the shape, color, depth of eyes, etc. of tubers should be critically examined and off-types discarded. In addition to off-types, the tubers with cuts, bruises, cracks, or otherwise mechanically damaged, or showing visible symptoms of late blight, dry rot, charcoal rot, wet rot, black scurf, etc. should invariably be removed.
Late blight affected tubers can be recognized by sunken purple spots on the surface, and the flesh has brown necrosis.
Packing:
After sorting and grading, the seed potatoes should be put in clean hessian bags (50 kg size) and the bags appropriately labelled.
Movement and Storage:
Soon after packing, the seed potatoes should be moved to the end-use areas for cold storage. If the ambient temperatures are above 32°C, the seed potato should first be kept in precooling chambers, or in a cool place for preconditioning, and then stored in cold storage at temperatures from 2.2 to 3.3°C and 75 to 80 per cent relative humidity. Periodic inspection of seed stocks in cold storage is necessary, to ensure that stocks are keeping good. Turning of bags during rainy season helps in improving aeration.