IDEA-NEW May, 2010 NOOR M NOORI

IDEA-NEW May, 2010 NOOR M NOORI

Potatoes are not roots but it is under ground stems called "tubers". Potato is one of the most important staple crops in the world In the Eastern Region, potatoes are grown and sold for both processing and fresh market

Climate It is a temperate zone crop with a wide range of seasonal adaptability. Young plants grow best at 24 C o, later growth is favored at 18 C o. For Tuber production maximum at 20 C o, and at about 30 C o tuber production stops entirely. Exposing tubers to light, results in sunscald and the production of solanine,

There are more than 100 cultivars of potatoes. White-skinned and red-skinned cultivars are the most common in Afghanistan. White skinned (Diamante, Kufri Chandramukhi (KCM), Kufri Lauvkar,) and red skinned (Desire and Cardinal). KCM and KL are short duration varieties with good storage quality.

The shape, appearance and yield of tubers depend to texture and physical nature of the soil. Potatoes can be grown on almost all types of soils For best Yield on light soils, well drained soils, rich in humus, is prefer Suitable ph 5 to 6.5. If potatoes are to be grown in clay soil, organic matter should be added and plowed deeply into the soil

A basal application of 4-6 T/jerib FYM should be applied. A basal application of 32-43 kg Urea, 21-34 kg DAP and 20-30 kg Potassium sulfate(k 2 SO 4 )/Jerib should be incorporated into the soil. If there is a micronutrient deficiency, a mixture of micro nutrient elements should be applied.

Potatoes are started from "seed pieces" or small tubers rather than from true seed. The seed pieces are tubers that have been cut into 42-56 g pieces. Each piece should have from one to three eyes (small sprouts). The pieces are planted 10 cm deep in raised seed beds.

The soil temperature at planting should be at least 7 C o but not over 21 C o. Soils should be moist but not excessively wet. potatoes can be covered with clear plastic when the soil temperature is low.

Seed rate depends on tuber size; 160-200 Kg/Jerib is generally recommended

The distance between rows is typically 60-75 cm, and 20 to 30cm apart in the row. Spacing is determined by the desired size of the tubers to be harvested and the cultivar used. The physiological age of the seed pieces affects the size and number of tubers produced. Avoid from planting of immature or not properly stored or handled Seed potatoes. If seed is known to be 'old', spacing should be increased

Water management is probably the most important factor determining yield and quality of potatoes. Many Diseases and disorders are directly related to the amount and the distribution of water during the growing season. Potatoes need frequent irrigation; the first irrigation should be immediately after planting, During the vegetative growth weekly base. After tuber formation, the frequency of water can be decreased Watering is stopped a few days before harvest.

Weeds should be removed as soon as they appear. After the potato plants have emerged, organic mulch can be applied. Pre-emergence herbicides can be applied just after planting and soon after the field is irrigated. The following products are pre-emergent herbicides that can be used: Nitrofen (Toke-E-25, 25%) @ 0.2 kg a.i. /jerib, Alachlor (Lasso 50%) @ 400 g a.i. or Simazine (Tafazine 50%)@ 0.1 Kg a.i./jerib.

Potatoes should be hilled or ridged to increase the depth of the seed piece. Tuberization starts 30-35 days after planting, Since tubers only form it is important that earthing-up be done at this time. Proper hilling is particularly important in clay soils because tubers tend to rise to the surface

Average potato yields in the Eastern Region were 3.5 T/jerib Now, with clean seed potatoes and improved agricultural practices, yields are reaching 4-6 T/jerib.

Insect Pests Potatoes are attacked by most of the insects which infest closely related solanaceous plants. Since potatoes are grown for their edible tubers, they must receive greater protection from pests.

The adult and nymph of the potato aphid are both solid pink, green and pink mottled, or light green with a dark stripe. They feed in colonies causing discoloration. They often transmit virus diseases such as PVY. Aphid populations are high during the spring cropping season (Feb-April) and less during the fall season (Sept- Dec),

Management of green peach aphid and potato aphid involves an integrated program of reducing overwintering populations. Controlling weeds in and around the field, and the use of foliar sprays. Monitor to schedule spray treatments.

The most common species encountered are the black cutworm and the variegated cutworm. Cutworms may cut off the stems of young plants during stand establishment. Later in the season they feed on foliage. Tubers that are exposed on the soil, or by cracks, or are set very shallow may be damaged.

Monitor the field to detect cut plants and foliar feeding early in the season. Later in the season, inspect plants for foliage damage. Treatment is necessary where worms are abundant and before the tubers are damaged. Two insecticides effective against cutworms are: carbaryl (Sevin) methomyl (Lannate)

It is attacks at two stages. In the early stages of plant growth. caterpillars mine or bore potato leaves and shoots, causing leaf blotches and killing the shoots. At harvest, moths lay their eggs on the tuber. When the eggs hatch, the larvae penetrate the tuber skin and make galleries through the flesh, leaving their excreta near the entrance holes.

Do not leave harvested potatoes in the field overnight. Store in sacks. Thoroughly clean storage places and spray with 1% Malathion or 0.6% Diazinon before storing potatoes. Plant disease-free potato seed. Plant seed tubers at least 20 cm deep and cover with about 25 cm fine, loose soil. Encourage specific Parasitoids, e.g. Copidosoma hochleri and Apanteles subandinus.

Numerous potato diseases and disorders may be caused by: bacteria fungi, viruses, phytoplasmas or may be physiological in nature. While prevention of the many diseases affecting potatoes vary widely depending upon the specific disease. Some practices apply generally to all diseases, These include the following:

Use certified seed. Handle seed properly. Follow a regular and precise sanitation program. When applying fungicides, follow the instructions on the label as well as the local authorities' recommendations. Irrigate uniformly and adequately, but not excessively.

Control aphids, leafhoppers, and nematodes. Harvest and handle tubers kindly. Do not harvest when tuber temperatures are below 7oC o or above 30C o. If storing, provide environment for wound healing, followed by proper temperature, humidity, and aeration. Warm cold tubers in storage before handling.

Early blight is primarily a disease of stressed or senescing plants. Symptoms appear first on the oldest leaves. Affected leaves develop circular to angular dark brown lesions 3 4 mm in diameter. Concentric rings often form in lesions to produce characteristic target-board effect. Severely infected leaves turn yellow and drop. Infected tubers show a brown, corky dry rot. Between crops, the early blight fungus can overwinter on potato residue in the field, in the soil, on tubers, and on other solanaceous plants.

Infection occurs when spores of the fungus come in contact with susceptible leaves and sufficient free moisture is present. Spore germination and infection are favored by warm weather and wet conditions from dew, rain, or sprinkler irrigation. Alternately, wet and dry periods with relatively dry, windy conditions favor spore dispersal and disease spread. Tubers can be infected as they are lifted through the soil at harvest. If sufficient moisture is present, spores germinate and infect the tubers

It can be minimized by maintaining optimum growing conditions, Including: proper fertilization- irrigation- and management of other pests. Grow later maturing, longer season varieties. Fungicide application is justified only when the disease is initiated early enough to cause economic loss. Apply fungicides (Mancozeb, Maneb) as soon as symptoms appear; continued protection requires application at 7- to 10-day intervals.

Late blight lesions can occur on all aboveground plant parts. On leaves, lesions typically first appear as small pale to dark green water-soaked spots that are irregular in shape and surrounded by a zone of yellowish tissue. Under favorable conditions, lesions expand rapidly and become brown to purplish black as tissue is killed. Under sufficient humidity, white sporulation of the fungus can be observed at the periphery of lesions, principally on the underside of leaves. On stems and petioles, lesions are brown to black and may also support sporulation of the fungus.

Infected tubers develop a firm brown decay that starts on the outside Inoculum of the pathogen can originate from: seed tubers- cull piles- volunteers- closely related weed hosts, and adjacent plantings of affected potatoes or tomatoes. Late blight can develop and spread rapidly if inoculums is present and conditions are favorable. High humidity (above 90%) and average temperatures in the range of 10 C to 25 C favor the disease.

PVY is one of the most prevalent and important viruses in potatoes. Recently, strains of PVY which can cause necrosis (dead spots on leaves and in tubers) have been discovered, creating more concern about this widespread virus. PVY is a Potato y virus, the type member of the largest group of plant viruses. It is transmitted by aphids in a nonresistant manner, by sticking to aphid mouthparts (stylet). The virus can be acquired from the infected plant within seconds, and transmitted to a healthy plant just as fast. PVY can also be transmitted mechanically by machinery, tools, and damaging plants while walking through the field. Aphids are by far the most efficient means of transmission. Necrotic symptoms in tubers often increase after storage

PVY can also be transmitted mechanically by machinery, tools, and damaging plants while walking through the field. Aphids are by far the most efficient means of transmission. Necrotic symptoms in tubers often increase after storage

Since PVY is a persistent virus and is transmitted quickly by aphids, the use of insecticides to control spread is generally not effective. The best strategy to control PVY is to use seed potatoes certified. Mineral oils can be used to reduce spread by aphids, but must be re-applied at frequent intervals to be effective. Rogue symptomatic plants of the Solanaceae family

1-Harvesting Harvest preparedness generally begins once tubers have reached a desirable size for the cultivar or market.

1-Harvesting Immature potatoes are easily bruised and "skinning" leads to shriveling or decay When the potato leaves start turning yellow and dry up, the crop has entered the maturity phase. Vines need to be cut or killed, two to three weeks before harvest

2-Grading Grading and standardization of the produce is essential as it brings higher income to farmers. For table use, tubers of comparatively big size are preferred.

Cut or injured and green tubers are not accepted by consumers. Oversized tubers are used for chips and medium size potatoes fetch a higher price. The basic qualities is seed potatoes The size may vary from 2.5-3.75 cm in diameter.

3- Marketing Potato is a perishable and bulky commodity with high water content and thus requires large storage and transport capacity. In cooler regions, storage is not a problem. Marketing in warmer areas involves handling and movement of potato under unfavorable environmental conditions.

4-Storage: Potato is a semi-perishable commodity. The cold storage has the capacity to store tubers for an extended period. The tubers can be stored at 1-2.7 o C and 90-95%RH. Farmers can store potatoes over the winter in a dark room at a temperature between (3 C and 4 C) with high humidity. Check periodically for spoilage. Temperatures below 3 C cause internal damage to the tubers

DERA MANANA