A Guide to Potato Cultivation: Detailed Information from Soil Preparation to Harvest Time

Potatoes, a annual crop, contain important nutrients such as carbohydrates in the form of starch, protein, vitamins, and iron (Fe) in their tubers. Potatoes are consumed directly in kitchens or processed into various forms (chips, french fries, etc.). Additionally, when potato flour is mixed into wheat flour at a rate of 3-5%, it enhances the taste of bread and delays staleness. Varieties with high starch content are used in industries (starch, alcohol, etc.), and some are also used as animal feed. Potato starch is widely used in the production of sausages and salami. Potatoes are highly consumed in European and American countries as a staple food, similar to the importance of wheat in our country. Potatoes are a hoeing plant, leaving the soil clean and aerated for the next crop. In coastal areas with a Mediterranean climate, where winters are mild, potatoes can be grown as early crops during the winter season, yielding high tuber production per hectare. These areas contribute significantly to the country’s economy by utilizing vacant lands in winter. The global average potato yield per hectare is 1719 kg, with an annual per capita potato consumption of 32.6 kg. This amount is 143.0 kg in Latvia, 132.1 kg in Poland, while in our country, the annual per capita potato consumption is 60.7 kg. The provinces with the highest potato production in our country are Niğde, Nevşehir, İzmir, Afyon, and Bolu, covering 39.5% of the total potato production.

Plant Characteristics

Potatoes are an annual crop that reproduces through tubers or seeds. When a potato tuber is planted in the soil, it develops roots, stolons, and tubers below the ground, and stems, leaves, flowers, fruits, and seeds above the ground. Therefore, the botanical characteristics of potatoes are examined in two parts: underground and above-ground organs.

Underground Organs

Roots: Potatoes have a fibrous root system and can reach depths of up to 1 m depending on soil and cultivation conditions. The root system of potatoes typically forms at a depth of 30-40 cm.

Stolons: During the formation of the potato plant’s underground root system, white extensions called stolons develop between the roots. These are called stolons, and tubers form as the tips of the stolons swell.

Tubers: The tuber formed at the end of the stolon contains eyes and tiny points called lenticels.

Lenticels: Lenticels serve as windows between the inside and outside of the tuber. Depending on environmental conditions, lenticels can open and close, allowing the entry and exit of water, CO2, and O2.

Eyes: Eyes are half-moon-shaped protrusions on the potato tuber that facilitate the development of new plants. The minimum number of eyes on a potato tuber is at the neck (where the tuber connects to the stolon), and the maximum number is at the crown (opposite the neck). The most developed eye in the crown is called the main eye, which has the dominance to sprout before others. When this eye sprouts, it prevents the other eyes from sprouting, known as apical dominance. If this eye is damaged or sprouts, the other eyes immediately start sprouting. Breaking the main shoot is necessary for the formation of multiple shoots on a tuber. The eyes on the tuber can be shallow or deep, which is a specific characteristic. For tubers intended for consumption (chips and french fries) and industrial use, having shallow eyes is a desirable feature. Potato tubers can have oval, round, round-oval, oval-long, or flat-cylindrical shapes, which are entirely variety-specific. The shape of the tuber is a specific characteristic. A potato plant produces 5-20 tubers, with the tuber size generally ranging from 5 to 500 grams. The skin color of potato tubers can be yellow, dirty yellow, brown, or red. The color of the skin is not necessarily related to the color of the tuber and flesh. When tubers first form, they are light yellow or pink and darken as they mature.

Chemical Composition of Potato Tubers

The main components of the composition of potato tubers are starch, protein, mineral substances, and vitamins. In culinary potatoes, a high starch content is not desirable because high-starch varieties disintegrate when boiled. Varieties with high starch content have white flesh. The color of the flesh is characterized by a high protein content, resulting in a yellow color. Additionally, solanine, an undesirable substance, is found in potato tubers. Solanine is produced under the influence of sunlight near the skin and is a toxic glycoalkaloid. For this reason, culinary potatoes should not be exposed to light. The color of the potato skin (yellow, dirty yellow, brown, or red) is unrelated to the color of the tuber and flesh. Tubers are light yellow or light pink when first formed and gain color as the skin develops.

Climate Requirement: Potatoes are a plant adapted to temperate and cool climates. The above-ground parts of the plant can tolerate temperatures as low as -1.5 ºC to -1.7 ºC, while the tuber can withstand temperatures from -1.4 ºC to -2 ºC; lower temperatures can cause damage to both the plant and the tuber. When the air temperature exceeds 30 ºC, the plants start losing a significant amount of water, and to regulate their water balance, they need to close their stomata. This results in the cessation of tuber growth. High temperatures accelerate vegetative development but delay tuber formation, leading to reduced yield. Potato plants require short days for tuber formation and long days for the development of flowers, fruits, and seeds. Increasing day length extends the plant’s ability to utilize light energy, resulting in higher yields. Long-day conditions enhance vegetative growth but delay tuber formation. Potato cultivation in our country is primarily conducted during the spring and summer seasons. Winter cultivation in warm climates can be practiced as early crops during the winter season, benefiting from the mild winters of the Mediterranean climate.

Photosynthesis provides the necessary energy, and as light intensity increases, photosynthesis and, consequently, tuber yield increase. As altitude increases, light intensity also increases, leading to increased tuber yield.

Soil Requirement

Potatoes can grow in almost all types of soil except extremely rocky and sandy soils. However, for optimal yield, the soil should be deep, well-drained, rich in organic matter, and loamy. The ideal soil pH for potato cultivation is around 6.0-6.5. Potato cultivation is not suitable in areas with high groundwater and saline (salty) soils.

Crop Rotation

Potato plants leave the soil clean and aerated for the next crop. It is not recommended to plant potatoes consecutively in the same field, as this can increase the intensity of soil-borne diseases, leading to a significant decrease in tuber yield. Potatoes can form an ideal crop rotation with soybeans, cotton, and cereals. In Adana, potato harvest begins at the end of April and lasts until the beginning of May. Planting peanuts as a second crop after potato harvest contributes to farmers’ income and protects the soil from erosion.

Preceding Crops

Crops like cereals and vegetables, as well as soybeans, are suitable preceding crops for potatoes.

Planting Time

Potatoes are cultivated in different regions of our country as both early and late crops. Early crops are grown in the Aegean and Mediterranean regions, and late crops are grown in the Black Sea and Central Anatolia regions. Early crops are planted in October-November and harvested in April-May. Late crops are planted in March-April and harvested in July-August. In Antalya and Mersin, early crops are also cultivated in the winter season. The most common planting time for potatoes in Turkey is February and March.

Planting Method

Potatoes are generally grown from seed tubers, which are small tubers used as planting material. The size of the seed tubers can affect the yield. Small seed tubers produce fewer stems and smaller tubers, while large seed tubers produce more stems and larger tubers. However, there is an optimal size for seed tubers, and excessively large seed tubers do not necessarily result in higher yields. Seed tubers should be disease-free and have a healthy appearance. The ideal seed tuber size is between 35-60 grams.

Seed Preparation

Before planting, seed potatoes are prepared by cutting them into pieces, each containing at least one eye. Cutting seed potatoes helps increase the number of plants and, consequently, the yield. It is essential to leave a piece of flesh with each eye, as the nutrients stored in this piece support the initial growth of the sprout. The cut seed potatoes should be treated with a fungicide to prevent diseases.

Planting Depth

Seed potatoes are planted at a depth of 10-15 cm, and the rows are spaced 65-80 cm apart. The spacing between plants within the row is 25-30 cm. The planting depth and spacing depend on the variety, soil conditions, and climate.

Fertilization

The nutrient requirements of potatoes are high, especially for potassium and phosphorus. Adequate fertilization is crucial for achieving high yields. The required amount of nutrients varies depending on soil fertility and organic matter content. Generally, for every hectare of potato cultivation, 300-400 kg of nitrogen (N), 200-300 kg of phosphorus pentoxide (P2O5), and 300-400 kg of potassium oxide (K2O) are recommended. The fertilizer should be spread uniformly before planting and incorporated into the soil. Additional nitrogen fertilization can be done during the growing season if necessary.

Irrigation

Potatoes require a significant amount of water for optimal growth. Adequate and timely irrigation is crucial, especially during tuber formation. Insufficient water can lead to irregular tuber shapes, reduced yields, and quality issues. Drip irrigation is recommended for potatoes, as it provides uniform water distribution and helps prevent foliar diseases.

Weed Control

Weed control is essential in potato cultivation, as weeds can compete with the crop for nutrients, water, and sunlight. Mechanical and chemical weed control methods are commonly used. Cultivation implements such as harrows and cultivators can be used for mechanical weed control, while herbicides are applied for chemical control. Pre-emergence herbicides are used before potato emergence, and post-emergence herbicides can be used after the crop has emerged.

Disease and Pest Management

Potatoes are susceptible to various diseases and pests, and effective management practices are necessary to ensure a healthy crop. Common potato diseases include late blight, early blight, bacterial wilt, and common scab. Pests such as Colorado potato beetle, aphids, and wireworms can also cause significant damage.

Harvesting

Potatoes are ready for harvest when the plants begin to yellow and the foliage starts to die back. The timing of harvesting depends on the desired end-use of the potatoes. For early crops, harvesting is typically done 90-120 days after planting, while late crops are harvested 110-140 days after planting. Harvesting is done using specialized equipment, and care should be taken to avoid damaging the tubers.

Storage

After harvesting, potatoes are cured for a short period to allow the skin to set and minor injuries to heal. Proper storage conditions are crucial to prevent sprouting, shrinkage, and spoilage. Potatoes should be stored in a cool, dark, and well-ventilated place. The ideal storage temperature is around 4-7°C with high humidity.

Marketing

Potatoes can be sold directly to consumers, grocery stores, or processed into various products such as chips, french fries, and starch for industrial use. Establishing a reliable marketing strategy is essential for maximizing profits.

Potato cultivation is an important agricultural activity with economic and nutritional significance. Proper management practices, including site selection, soil preparation, planting, fertilization, irrigation, and pest control, are essential for successful potato production. Continuous monitoring of the crop and timely interventions contribute to high yields and quality potatoes. Additionally, implementing crop rotation and other sustainable practices helps maintain soil health and reduce the risk of diseases.