The potato (Solanum tuberosum) is an herbaceous annual that grows up to 100 cm (40 inches) tall and produces tubers, which are botanically thickened stems that are so rich in starch that they rank as the world's fourth most important food crop, after maize, wheat and rice.
The potato belongs to the Solanaceae and shares the genus Solanum with at least 1,000 other species, including tomato and eggplant. S. tuberosum is divided into two, only slightly different, subspecies: andigena, which is adapted to short day conditions and is mainly grown in the Andes, and tuberosum, the potato now cultivated around the world, which is believed to descend from a small introduction to Europe of andigena potatoes that later adapted to longer day conditions.
Quality parameters of potato yield
Potatoes are consumed fresh or processed to chips and crisps. Potatoes are also used to produce starch.
Potatoes grown for processing are valued for yield, size, shape, and mainly for dry matter content (measured by specific gravity). As the specific gravity increases, the water content of the potato decreases, improving the frying properties and flavor. Management factors, including plant nutrition, influence potato yield, quality, and storage properties.
Potato growth stages
Potato growth is classified into five distinct growth phases, each one features specific growth processes and requires different nutrition:
 | Stage I: Sprout development Sprout develops from eyes on seed tubers and grows upward to emerge from the soil. Roots begin to develop at the base of emerging sprouts. |
 | Stage II: Vegetative growth Leaves and brunch stems develop from aboveground nodes along emerged sprouts. Roots and stolons develop at below-ground nodes. Photosynthesis begins. |
 | Stage III: Tuber initiation Tubers form at stolon tips but are not yet appreciably enlarging. In most cultivars the end of this stage coincides with early flowering.
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 | Stage IV: Tuber bulking Tuber cells expand with the accumulation of water, nutrients, and carbohydrates. Tubers become the dominant site for deposition of carbohydrates and mobile inorganic nutrients. |
 | Stage V: Maturation Vines turn yellow and lose leaves, photo-synthesis decreases, tuber growth slows, and vines eventually die. Tuber dry matter content reaches a maximum and tuber skins set. |
The exact timing of the growth stages depends on many environmental and management factors that vary between locations and cultivars. However, these distinct stages of growth need to be considered when managing the crop.
Potato growth conditions
Soil
Potatoes grow on most soils – organic as well as mineral ones. However, light and medium texture soils are recommended where mechanical harvesting is practiced, to avoid difficulties in harvesting when weather conditions are adverse at harvest time.
Soil pH should be above 5.5. Soil pH below 4.8 generally results in impaired growth.
Too alkaline conditions can adversely affect skin quality and might induce micronutrient deficiencies.
Irrigation
During the early growth phase, until tuber formation, it is essential to keep the soil constantly and uniformly wet to a depth of at least 10-15cm. The frequency of irrigation cycles during this period should be determined according to the specific soil type and climate conditions.
During the second growth phase, during tuber development, irrigation will be less frequent and applied once every 3-5 days. This allows efficient root respiration and intensifying growth rate. Potatoes can be irrigated almost until harvest.
Irrigation at tuber initiation can affect the skin quality of daughter tubers by influencing phytopathogens, either favorably or adversely, according to conditions, and moisture rate present.
A monitored drip system equipped with a Nutrigation™ (fertigation) device is the preferable method of irrigation.
Special sensitivities
Chloride: The potato plant is sensitive to the presence of chloride in soil and irrigation water. Chloride damage is manifested by scorching of the leaf tips and margins, and leaves yellowing and distortion. Chloride-free fertilizers support the plant’s healthy growth, increasing yield improving tuber quality.
Boron deficiency: Insufficient boron supply during tuber growth may lead to “Hollow Heart” – formation of cavity near the tuber centre. As this disorder occurs without any external indication, it is advisable to monitor boron levels, particularly during the relevant phases. Note that rapid tuber growth, sometimes resulted from low plant density, may cause this syndrome, too.
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