Potato

 

Seed Production Technology

There are now two independent channels of seed production for hills and plains.
Hill Seed: The seed produced in hills (2500 metres above sea level) at suitable locations iscalled'Hill Seed'.

Plain seed: The seed produced in plains at suitable locations is called ;plain seed'. Northern plains have emerged as an important source of potato seed production. The low aphid plains seed is in right physiological condition at the planting time and yields higher than the traditional hill-grown seed. The period of low aphid incidence is given below.

Plains zone                                   - Low aphid incidence period
North western plains                     - Oct. to end of Dec.
North central plains                       - Oct. to 10th Jan.
North eastern plains                       - Oct. to 20th Jan.
One healthy seed potatoes are introduced into the system of grwoing them during low aphid period accompanied by a systematic insecticide application, roguing and removal of haulms before the aphids attain critical number and the regrwoth is checked, the health standards for the seed cropcould be maintained for a number of generations. This system of seed potato production has been designated as ;Seed Plot Technique'.
Seed Production in Eastern Plains, Deccan Plateau and Southern latitudes. In these areas the effective low-aphid period is practically absetn. In such situations, reasonably healthy seed consistent with economic yeidl could be produced by using systemic insecticides to reduce the build up of insect vectors and to prolong the growing season of the crop. It should thus be not obligatory to replace seed annually in large quantities from the northern states. Seed could be imported in smaller quantities every eyar and multiplied for one to two clonal generations.
Seed Production in the Nilgiris: In the Nilgiris, aphid population is lower during summer crop only from those areas which are free from cyst-forming nematodes. The treatment of the seed potatoes with sprout suppressants like CIPC and Fusares, at the rate of 0.5kg per quintal can maintain the seed sotcks in good physiological condition in farm stores in the absence of cold storage facilities. thus the seed stocks from the summer crop can be stored without deteriorationuntil the next planting season that is, September to March-April.

Stages of Seed production: For seed multiplication and certification purposes following stages arerecognised.
Foundation I : Progeny of the breeders seed
Foundation II: Progeny of the foundation I
Certified I : Progeny of the foundation II
Certified:II* Progeny of the certified I
(* This is done in case ofthose vareities which have a low rate of multiplication and in years of shortage of seeds)

  

 

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 noncyst forming nematodws within the previous three years; and common scab. Preference should be given to two to three year crop rotation. the soil of 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 5 metres for foundation and certified seed class should ber provided all around a seed field to separate it from fields of ther vareities,and fields of the same vareity not conforming to varietal purity and health requirements for certification.

Cultural Practices

 

Time of Sowing The sowing should be done from 20th September (when rainfall is low), or 25th September, upto 15th october .Delayed plantings well result in poor yields.
  


Preparation of Land . Prepare the field to a fine tilth by deep ploughing, 3 to 4 harrowings, followed by levelling.


Source of Seed Obtain breeder's/foundation seeds from source approved by a seed certification agency.


Seed Rate seed rate depends upon tuber size. 25 to 30qtl of seed potato per hectare will be sufficient if the usual sized tuber (4 to 6 cm) are used.


Sowing of Seeds Whole tubers should be used for planting. Tubers should be under sprouting (sprouts 0.5 to 1cm long) for quick emergence. After 15th October when the temperature goes down, cut tubers can also be sued for planting, as per prevailing local practices. Care must be taken that each piece to be used for planting has two or three emerging eyes and weighs at least 40 gm. by this practice the seed rate isreduced considerably. Plant the tubers 3 to 4 cm deep in the soil having adequate moisture. At planting, tubers should not come into direct contact with fertilisers which should be placed right below the seed potato.


Fertilisation For a good seed crop, the medium type of soils need 100 to 125 kg nitrogen, 80 to 100 kg phosphorus and 80 to 100 kg potash per hectare. Variations may be made according to the soil tests. Besides the fertilisers, farmyard manure may be added at the rate of 25 tonnes per ha, 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. Theremaining half of nitrogen should be applied about 35 days after sowing, or when the plants are about 25 to 30 cm high. For best results,the fertilisers should be placed either 5 cm below the tubers, or on the side.


Irrigation Potato requires light and frequent irrigation. First irrigationshould follow imemdiately after emergence. Subsequent irrigations should be given at proper intervals. the top of the ridges should not be submerged. Restrict the irrigation after the crop has tuberised well. Withhold irrigation by thethird week of December i.e., ten tofifteen days before cutting of haulms.


Interculture Keep the field free from weed.s At least one earthin-up is a must. It should be done when plants attain the height of 15 cm. Exposed tubers should be covered with soil during subsequent earthin-up.


Insect and Disease Control Adopt recommended IPM methods


Spacing Row to row spacing at 60 cm and tuber to tuber spacing at 15 to 20 cm is recommended.


Haulm cutting

The practice of haulm cutting is adopted as a precautionary measure to avoid chances of viral diseases transmission through the vectors like aphids. The haulms must be cut bythe 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 25 days after sowing to remove.
a) All virus affected plants, and (b) All plants apparently belonging to other varieties and 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 removedcarefully. Also at thisstage the virus-affected plant as well as off-type, if any, should be removed.
Third roguing: This isthethird and final roguing and should be done just before cutting the foliage. Foliage should not be cut unless this rouging has been completed. At thisstage, all virus-affected lants and off-type plants, if any, along with their tubers have to 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 10 to 15 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 longtransportation and storage.
b) Soil conditions at the time 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 hotsun 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 metre, width threemetres) for seven to ten days so that the superficial moistureevaporates and furtherhardening of skin is achieved. If sheds are notavailable, piles may be made in fiedl and covered with dry haulms.		  


Sorting and Grading When the potatoes are properly cured, grading should be done.

After sorting and grading the seed potatoes should be put inclean hessian bags (50 kg size) and the bags appropriately labelled.