Potato

Field Preparation

Field should be thoroughly ploughed to obtain a good tilth. It should be leveled for uniform distribution of irrigation water or to maintain soil moisture uniformly under rainfed situation. The furrows should be prepared at 60 cm apart. About 20 cm spacing should be maintained between two tubers in rows.

Method of Planting

The sprouted tubers should be planted in furrows with sprouts facing upward. Care should be taken to avoid sprout damage during handling the tubers.

Seed Selection

Virus free, healthy, medium-sized sprouted tubers are to be selected for planting. Ideal size is about 2.5 cm in diameter (25-40 g). Bigger-sized tubers may be cut into pieces longitudinally with 2-3 eyes in each piece.

Seed Sources

Certified seeds of the recommended varieties are to be procured from Govt. or other recognized agencies.

Seed Treatment

In case of cut seeds, the pieces are to be dipped in carboxin @ 2g in 1 litre of water for about 10 minutes. After treatment, the seeds are to be spread thinly and dried under shade for 48 hours, or should be covered with moist gunny bags for 2-3 days for tuberization.

Seed Rate

The seed requirement is 22.5-25 q/ha when the size of the tubers is about 2.5 cm in diameter (about 25 g) and planted with an intra-row spacing of 15 cm. Intra-row spacing is increased with bigger-sized tubers.

Nutrient Management

Ten tonnes or 5 truckloads or 20 cart loads of well decomposed FYM should be applied per hectare in the furrows before planting.

Entire quantity of fertilizers should be applied in furrows as basal application and be covered with a thin layer of soil so that tubers do not come into direct contact with the fertilizers. The crop booster ‘Green Harvest’ is recommended @ 25 g/10 lit of water at 30 days after planting.

Mulching

Application of mulching under rain situations increases tuber yield. Generally, water hyacinth is applied to cover the entire field after planting of tubers under the flatbed method. However, the skin of the tubers may turn green due to exposure to sunlight or shrinkage of mulching materials on drying. Tubers become unsuitable for consumption due to greening; however, quantities may be reduced by applying mulching materials in furrows just after planting of tubers, immediately.

Water Management

The furrow method of irrigation should be adopted. Three irrigations should be applied: first at 25 days (stolon formation stage), second at 60 days (tuber formation stage), and third at 80 days (tuber development stage) after emergence of sprouts. In case of application of mulching materials in furrows, only two irrigations are to be applied at 25 and 60 days after emergence of sprouts. At the time of application of irrigation, care should be taken not to submerge the ridges completely.

Weed Management

Earthing up is to be done just before the first and second irrigation. Under rainfed conditions, this should be done at stolon and tuber formation stages. One or two interculture operations may be necessary when weed infestation is high. Apply metribuzine @ 0.75 kg/ha (100 g/bigha) at 10% plant to get optimum weed control.

Practices for On-farm Storage of Seed Potatoes

• Harvest seed tubers from fully matured potato crops.
• Among the different tuber grades, small-sized (5-15g) tubers can be kept suitably in on-farm stores compared to big-sized tubers (>20g).
• Loading density of 75g/m² proved beneficial than higher loading density for stored tubers under traditional stores.
• Seed potatoes collected from the main field should be cured properly for 10-15 days in cool place and then treat the healthy tubers with 3% boric acid for 30 min followed by 0.2% copper oxychloride for 20 min. After shade drying, the tubers should be loaded in the bamboo rakes fitted in the store.
• After shade drying, the tubers should be loaded in the bamboo racks fitted in the store.
• Use a 4cm thick layer of shade-dried 'Neem' or Eucalyptus leaves under and over the tubers.
• Stored potatoes should be covered with mosquito nets in PTM endemic areas.
• Frequent inspection of the tubers in the store is essential. Remove the rotten tubers periodically.
• Sprout breaking during August is essential in order to minimize over-shrinkage and shriveling of tubers.

Package Of Practices For Growing Of Potato Crop From true Potato Seeds

The potato crop can be grown from True Potato Seeds (TPS). The three methods are as follows:

Transplanted Crop:

Seedlings are transplanted in the field after raising in the nursery. About 70% of the total produce is marketable and the remaining quantity of small-sized tubers is used as seedling materials in subsequent seasons.

Tuberlet Production:

TPS are sown in nursery beds and 70-80% is produced as tuberlets, which are used as planting materials.

Planting of Tuberlet:

Mainly commercial tubers are produced on planting of tuberlets, though tuberlets can be used as planting materials during subsequent years.

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Characteristics of the Varieties:

1. Resistant to Late Blight disease
2. Reduced pathogen transmission
3. Higher yield potential
4. Tuber space may be round and oval
5. Skin smooth with fleet and medium deep eyes

Transplanted Crop: Preparation of Nursery Bed for Raising Seedling

• Make the nursery beds of one-meter breadth and of convenient length (preferably 3 m).
• Prepare a raised nursery bed by filling 7-8 cm with soil, FYM substrate. Prepare the substrate for the seedbed by mixing sterilized soil and well-rotten and dried FYM or compost or bio-gas slurry in a 1:1 ratio. Apply fertilizer @ 4-5 g N, 6-8 g P2O5 and 10 g K2O/ sq.m in the substrate and mix thoroughly. After 2-3 days, the bed is ready for sowing of TPS. The soil could be sterilized by drenching the soil with 4% formalin followed by covering with polythene or locally available materials (like banana leaf/ straw etc.) for 72 hrs. and then remove the cover.
• Cover the top of the nursery beds with 2-3 cm thick layer of finely sieved FYM. Thus the nursery bed is raised to about 10 cm from the field level.

Seedling Raising:

• Prepare the seeds for sowing in nursery during the 1st week of October (TPS germinate well when the daily minimum temperature touches 20°C and maximum temperature is 30°C).
• Soak the TPS in water for 24 hrs. and then incubate in FYM + soil mixture (1:1) for 2-3 days. Pre-germinated seeds are to be sown in the nursery bed.
• Lightly irrigate the nursery beds a day before TPS sowing to keep the bed in moist conditions.
• Sow the pre-germinated TPS in 0.5 cm deep furrows drawn 10 cm apart across the breadth of the bed @ 2 g seeds/sq.m and cover these with a 0.5 cm layer of finely sieved FYM. Seedlings raised per 10 sq. m nursery can cover 1500-1600 sq. m area. About 120g TPS and a nursery bed area of 75 sq. m are required for raising seedlings for transplanting in one hectare. Sprinkle water on the seedbeds 2-3 times a day for about a week after sowing the TPS using a sprayer or a gardener’s water can to keep the seedbed moist (avoid excess water). Care should be taken so that seeds are not distributed during irrigation and to avoid runoff waters. Subsequently, sprinkle water once or twice a day.
• Protect the nursery beds from direct bright sunlight by providing thatch grass shade during mid-day for 10-12 days after sowing. Remove the cover in the late afternoon and put it by morning (8-10 am). However, shade should be provided to protect the seedlings from rain whenever necessary.
• The nursery bed should be weed-free.
• After the germination is completed and the leaves start emerging (around 10 days), spray the seedlings every 4-5 days’ interval with 0.1% urea (prepared by dissolving 1g urea in 1 litre of water) till these are ready (4-5 leaf stage) for transplanting. The seedlings are ready for transplanting after 25-30 days of sowing.

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Field Preparation and Seedling Transplanting:

• Prepare the field as per normal recommended practice.
• Basal application (broadcasting) of N, P2O5, and K2O (60:100: 100 kg/ha) at the last round of field preparation. Apply FYM @ 10 t/ha during field preparation.
• Prepare the ridge at 50 cm apart in the East-West direction. Irrigate the furrows one day before transplanting of seedlings. However, irrigation may not be applied if sufficient moisture (around field capacity) remains in the soil, particularly on ridges.
• Carefully uproot the seedlings from nursery beds and carry them to the field in a basket. Transplant one seedling per hill in north-facing ridges at 10 cm spacing. Transplanting should be done preferably in the afternoon.
• Irrigate the furrows after transplanting to keep the soil moisture in the root zone (ridge) at field capacity. While irrigating, care should be taken not to submerge the seedlings. Irrigate the crop every third/fourth day subject to the moisture condition of the soil, till the seedlings get established. Thereafter, the frequency of irrigation can be restricted to one in 8-10 days.
• Gap filling should be done within a week of transplanting.
• Spray 0.2% dursban on the 4th day after transplanting to protect the seedlings from cutworms.
• Light manual interculture operation (using khurpi) to be performed at about 10 days to loosen the soils in the root zone.
• Earthing up should be done 20-25 days along with the application of 25 kg of N/ha. Care should be taken during earthing up so that seedlings come to lie in the center of the ridges and maximum nodes are covered with soil leaving open the top 5-6 upper leaves.
• Second earthing up should be done at tuborization stage (45-50 days). The remaining cultural operations to be followed are similar to standard cultivation practices for the potato crop. However, fungicides should be applied only when disease symptoms are visible on the leaves.
• De-haulm the crop after 105-110 days of transplanting.
• Harvesting is done 10-12 days after dehaulming.

Seedling Tuber Production:

To produce seedling tubers, follow the procedure below:

• Add NPK fertilizers @ 60:100:100 kg/ha to the FYM substrate and mix properly.
• Irrigate the nursery beds a day before sowing of TPS.
• Mark the rows in the nursery beds at 10 cm inter-row distance. Sow 2-3 seeds at 10 cm intra-row distance at a depth of 0.5 cm and cover them with a 0.5 cm thick layer of fine sieved FYM.
• Irrigate the seedbed twice or thrice a day or as needed for a week after sowing, using a water cane or sprayer, ensuring that the soil is kept moist (field capacity) without any runoff water. Subsequently, irrigate once or twice a day to keep the beds moist.
• Provide shade initially as mentioned in earlier methods to protect from rain, bright sunshine, etc.
• After 10 days of emergence, spray the seedlings with 0.1% urea on every third or fourth day for boosting up the growth and vigor of the seedlings. Spraying of urea solution should be stopped when the seedlings become vigorous.
• When the seedlings attain a height of 15cm, cover the lower-most three internodes of the seedlings with additional quantities of substrate mixture and repeat the earthing up three times at an interval of 7-8 days.
• Proper and timely weeding is essential. Follow the usual cultural irrigation, plant protection, etc.
• Cut haulm at the age of 90-95 days.
• Harvest the seedling tubers after 12-15 days of haulm cutting.

Cultivation of Potato Crop from Tuberlets:

The seedling tubers produced either by direct seeding of TPS or from the transplanted potato crop are planted in the field in the next season. The method is similar to the recommended conventional cultivation practices of the potato crop, except the spacing according to seed rate and seed size.

In case of 5g, two tuberlets should be planted. Moreover, seedling tubers (tuberlets) can be used for 3-4 successive years if the seed plot technique is followed appropriately.

Zero- tillage potato cultivation technology in Assam

Zero- tillage potato cultivation technology means that planting can happen immediately after the paddy harvest, with no land preparation, earthing-up, or digging of the soil at harvest. It conserves soil moisture and extends the days available for potato cultivation to fit in the short window between the two rice seasons and above all does not compromise yield compared to using conventional methods. It also enables farmers to save about 30% on cultivation costs.

Conventionally, farmers wait for about a month after the paddy harvest to prepare land for potato cultivation which further shortens the available window and means the crop faces a delay in planting and harvesting. From February to March the temperature starts to rise which impacts yield and the storability of the crop.

ZTRM allows farmers to eliminate the time required for land preparation and is useful for sowing potatoes within a few days of rice harvesting. Moreover, it is a technology that eliminates the entire cost of land tillage and digging and significantly reduces the costs of inputs and labor (Table 1). It is a quite simple and cost-effective technology for farmers to use and it also means that a long- duration potato variety can fit into the available time window quite easily. Another big advantage of ZTRM is the availability of rice straw after paddy harvest which can be used for potato cultivation rather than burned, creating an additional benefit for both the farmers and the environment.

Zero-tillage with rice mulch technology

One of the basic requirements for zero-tillage with rice mulch (ZTRM) is the availability of plenty of soil moisture at the time of planting. Moisture content in Assam soils is high and the evaporation rate is low because of prevailing high humidity. Rice mulch further reduces soil surface evaporation. As a result, in many areas crops can be grown without any irrigation or with one or two very light irrigations.

Immediately after the rice harvest, potato crops can be planted as no soil tillage or other preparations are required. Well-sprouted seed tubers are placed directly on the soil in rows at 50 x 25 cm spacing, while farmyard manure is placed on the tubers and chemical fertilizers are placed between the rows of tubers. All chemical fertilizers are applied as a basal dose at the time of planting. After 30 days of plant growth, water-soluble fertilizers and micronutrients are applied as foliar spray (Table 2). Tubers are covered with a 15-20 cm thick layer of paddy straw or 4-5 kg of rice straw/m2. For mulching one bigha of the zero-tillage potato crop, rice straw from 3 bighas can be used. Potato plants come out of the rice straw in 15-20 days and rapidly grow to cover the entire available area. Weed growth is practically nil due to the thick rice mulch. Needs-based chemicals or bio-pesticides are applied. Mulching results in a 90% reduction in cutworm incidence and the onset of late blight is also delayed due to changes in the crop’s microclimate. The crop is harvested after 75 to 90 days by removing the mulch and picking the tubers from the soil surface. Again, no digging of the soil is required – see Images 1, 2, and 3.

Table 1. Comparison cultivation costs: Conventional tillage v zero tillage per bigha (1,333m2)

Table 2. Fertilizer requirement per bigha (1,333m2)