Species: Solanum tuberosum L.
French: pomme de terre; English: potato; Spanish: potato; German: Kartoffel.
Origin and diffusion
The potato is native to the Andean regions of central-southern America. It was introduced in Europe after the discovery of America, first as a botanical curiosity and then as a food plant. Cultivation in Italy began in the early nineteenth century, although its true diffusion was later (end of the century).
Potato cultivation is widespread all over the world with a greater concentration of surface in Europe (in particular Poland, Germany, Czech Republic, Spain and France), where in some countries unit yields are reached which are among the highest and where it represents , for many populations, the staple food that replaces bread. It interests the food industry for the production of starch, starch, dextrin, glucose as well as distillation and is used in zootechnical feeding. The market also requires products suitable for canning and the production of fried (frozen) potatoes.
With the potato, three types of crops are made in Italy: the early or early one (concentrated in particular in the South), the common one (in particular in the North) and the leap or second harvest one, which occupies a limited area. Italy is at the same time an exporter (early product) and an importer (common product and seed tubers).
Potato is an annual cycle plant with rather superficial collated roots, equipped with numerous capillary branches. The stolons depart from the hypogean part of the stem which, enlarging at the apex, give rise to a tuber. The ability to originate a different number and length of stolons varies according to the variety and environmental conditions.
In a fully mature tuber the epidermis is replaced by the periderm (or peel) made of layers of suberose cells, which protects the inside of the tuber from excessive water loss and the penetration of fungi and bacteria. Inside, both the bark and the marrow and the parenchyma that makes up the majority of the tuber have become the site of accumulation of large quantities of starch. In the midst of this mass of tissues, different but not more easily distinguishable, there are fibrovascular bundles directed towards the "eyes". Under the influence of light, the external tissues of the cortical parenchyma produce chlorophyll and green.
The tubers can differ in size, shape, number, color, characteristics of the external tuberous tissue, color of the pulp. In the tuber there is a navel (point of attachment of the stole) and a head, opposite to the navel, which collects most of the buds. If any gems are suppressed, this is replaced by another replacement. Not all the buds of a tuber, when buried whole, develop giving rise to a stem. The most vigorous are those on the head.
The area part of the plant is generally made up of two or more stems, angular, fistulous, enlarged at the nodes, of various length and color, with erect bearing or more or less decumbent.
The leaves are composed of 5, 7, 9 leaflets of various sizes and colors (light to intense green), more or less bullous and with a more or less open foil. The green parts - including the tubers when they remain exposed to light for a long time - contain solanine, poisonous alkaloid.
The lymph flower is a corymb. The flower is hermaphrodite, campanulate. Some potato varieties, regardless of the environment, do not bloom; others instead come to issue flower buds, which however fall before flowering; others finally bloom regularly and ripen the fruits (more or less round fleshy berries, green-brown, green-violet or yellowish, containing 150 to 300 reniform, flattened seeds).
For plants that originated via agamic it normally lasts 100-150 days.
Plants that derive from seed have a considerably longer cycle (180-200 days). For this reason, in our environmental conditions, a first greenhouse breeding is necessary. However, gamic reproduction is used in potatoes only as a means of varietal improvement.
After a period of rest (50-60 days after maturation), tubers germinate under suitable conditions (temperature above 6-8 ° C). The vegetative phases of the plant to the effects of cultivation are: emergence, vegetative growth, flowering, growth of tubers, maturation of tubers. The formation of the tubers begins just before the appearance of the flower buds and manifests itself with an enlargement of the stolons or their ramifications. The ripening phase is characterized by the gradual yellowing of the leaves and stems, as well as by the change in color of the berries (if they are present) which turn from green to yellowish, while the peel of the tubers tends to become increasingly difficult to detach from the pulp. Subsequently the leaves and stems dry out and the berries fall off. Harvesting can take place at an early age for ready-to-eat tubers and for those destined for propagation. For those in common use, the excavation may be delayed.
The potato is a species suitable for the temperate-cold climatic zone: the areas best suited to
pathiculture are the great plains of north-central Europe; in Italy favorable areas are
those of the mountains of the Alpine, pre-Alpine and Apennine regions. In these conditions the potato has a spring-summer cycle. Only in southern Italy the potato is planted in autumn to collect its production, early, in spring.
The tubers freeze at -2 ° C. The vegetation zero is at 6-8 ° C. Spring cold returns (less than 2 ° C) are fearful. High temperatures, near or above 30 ° C, greatly reduce assimilation.
The plant needs, in every biological phase, a sufficient quantity of water. The water requirements diminish near the maturation. The potato is very afraid of excess humidity and the consequent water stagnation which favors the development of cryptogamic diseases, causes the malfunction of the roots and the irregular development of the tubers.
Ideal are siliceous or siliceous-clay soils, slightly acidic, light, loose, permeable, deep. The potato also adapts to fairly fine-grained soils, as long as they are well structured and well draining. In clayey soils, the collection of tubers is more difficult and their quality is inferior (irregular shape, rough and dark skin). The potato shuns the alkaline soils.
Virtually all potato varieties grown in Italy are foreign, some of which are cultivated
for about a century.
Some potato cultivars most popular in Italy and their characteristics:
- Bintje: semi-early cycle; plant with few stems; scarce, white flowers; ovoid tubers with shallow eyes; yellow peel, yellow paste; good for all types of cooking, but particularly for fried potatoes.
- Désirée: semi-late cycle; plant with numerous red-brown stems, abundant red or violet flowers, oval tubers, with red skin and yellow paste; firm paste, resistant to cooking; especially suitable for french fries.
- Jaerla: medium-early cycle; plant with few stems, light green leaves, flowering
poor with white flowers; very large oval tubers, yellow skin, yellow paste, shallow eyes.
- Kennebec: medium-late cycle; plant with few stems, very little flowering and white flowers; tubers
rounded, very large, with superficial eyes, light skin, white paste, good taste,
- Majestic: semi-late cycle; plant with few stems, abundant flowering, with white flowers; elongated and thick tubers, yellow skin and white paste; has good culinary characteristics; varieties of ancient cultivation in Italy.
Monalisa: medium-early cycle; plant with few stems, pale violet in color, poor flowering with white flowers; tubers of large size, slightly elongated shape, yellow skin and yellow paste; the size of the tubers is uniform and with good culinary characteristics.
- Primura: early cycle; plant with few stems; oval, uniform, yellow-skinned and yellow-paste tubers.
- Spunta: medium-early cycle; plant with numerous stems; abundant flowering with white flowers; long tubers, rather pointed and often arched, with yellow skin and yellow paste.
Potato tubers (website photo)
The early potato is sown from December to February and is harvested from April to June; the common one takes place from March to August in the plains and from May to September in the mountains. The second crop is done after a main crop in spring or summer and has a cycle that goes from August or September to November or December.
As regards rotation, the potato, in normal and early conditions, normally occupies the first place (crop for renewal). The so-called leap or second harvest potato occupies the place of interlayer cultivation in the summer-autumn cycle. In the plain it can be found in horticultural rotation or in normal rotation with wheat and leguminous meadows. In the mountains it most frequently alternates with rye.
The potato does not admit to entering short rotations: 4 or even 5-6 years must pass before the potato returns to the same ground, nor in this time must other rotations of solanaceae (tomato, pepper, eggplant, tobacco) enter the rotation. Short rotations favor the development of terrestrial pathogens (rizottoniosis, helminthosporiosis, nematodes) and lead to unacceptable production reductions.
The soil intended for the potato must be worked in depth in the summer (40-50 cm), thus also making the organic substance burial.
Allaratura is followed by an adequate harrowing in order to perfect the seedbed. With the latest preparatory interventions, the soil surface can be perfectly leveled (for subsequent mechanized sowing) or furrowed (for hand sowing).
A potato crop under balanced nutrition conditions to produce a ton of tubers requires 4 kg of nitrogen, 1.5 kg of phosphorus pentoxide and 6 kg of potash.
The potato has very high needs for phosphorus, very high for potassium. Potassium facilitates the synthesis of carbohydrates in the leaves and the translocation of these into the tubers. A good potassium diet improves the quality of the tubers, for example by lowering the reducing sugars. Phosphorus is an earliness factor and promotes radical development. The fertilizers of phosphorus and potassium that are most commonly done to the potato are the following:
- phosphorus (P2O5) 70-100 kg has 18-20 or triple superphosphate as superphosphate;
- potassium (K2O) 200-300 kg ha better as potassium sulphate.
Phospho-potassium fertilizers must be buried if not with laratura, at least with one of the complementary winter jobs.
Lazoto is the most important element as it determines the brightness of the leaf apparatus and its photosynthetic efficiency, factors on which the accumulation of starch in the tubers is based. However, excess nitrogen promotes excessive leaf development at the expense of tubers, delays their maturation and decreases their dry matter content.
Nitrogen administration must take place fractionated, partly before the seed is buried (50%), partly with sowing localization, and on the roof, shortly after the complete emergence of the plants. The form of nitrogen which is best suited is ammonia.
The potato is a crop capable of reaping the maximum benefits from fertilizing with manure, administered before winter.
Choice of seed potatoes and sowing (although it would be better to talk about planting)
Thick tubers with many eyes form a cluster of numerous stems among which the competition is strong; the opposite in the case of small tubers. The degree of competition at the underground level determines the number and size of the tubers: the thick tufts derived from large tubers form many tubers but of small size, and vice versa. This is important for producing tubers of the most requested size (small for seed tubers, medium for direct consumption, large for certain transformations).
The planting density must therefore be defined not so much as the number of seed potatoes placed at
dwelling per square meter, but as the total number of stems that will originate from it. The optimal number is around 15-20 stems per square meter. For this reason, and also for economic reasons, seedlings of modest size (generally 50-80 g) are used for planting. A practice to save on the quantity of seed is the splitting of the tubers.
The tubers can be sprouted before sowing, arranging the seed tubers in cassettes stackable in no more than two layers, in an environment well lit by diffused light, not too dry, at a temperature between 12 and 16 ° C. Normally, after four to six weeks from the eyes of the tubers short shoots (15-20 mm maximum), stubby, robust, pigmented are born: the seed tubers are ready for planting which must be done with great care to avoid breaking the shoots. The pre-sprouting allows to anticipate the beginning of the vegetation and makes possible a last control of the seed from the point of view of the vegetative vigor. The quantity of tubers normally used for sowing is 20-30 quintals per hectare.
The tubers are 25-30 cm apart in the early crop and 30-35 cm apart in the other types of culture. The distance between the rows is 60-80 cm. The sowing depth is 5-8 cm in relation to the nature of the soil.
Sowing can be done by hand or with planters, with which the operation is partially or completely mechanized.
In soils subject to incrustation, in relation to the climatic trend, weeding is useful as soon as the rows are clearly visible on the ground. The operation is also effective as a supplement to the chemical fight against weeds.
Ridging - tamping consists in placing the inter-row ground on the row of potato plants in order to favor the release of rhizomes and roots from the buried part of the stems. It is done in one or two steps in the 2-3 weeks following sowing with the shoots at the stage of 2-3 leaves forming a 20 cm high sloth on the countryside level: this ensures optimal conditions of development for the roots, rhizomes and to the tubers-children. The tamping promotes rooting, tuberization and nutrition, avoids greening of
tubers and protects these, albeit partially, from the infection of the downy mildew spores fallen on the
Irrigation - The potato has quite high water needs during a period of the year when rainfall is low. Its shallow root system, with weak penetration and sucking capacity, make it sensitive to water stress. In Italy irrigation is indispensable in central and southern areas, while useful (although not indispensable) in northern regions or in regions of altitude where the water deficit is less marked. The critical period for water goes from 20 days before to 20 days after the beginning of the antesis, when the potato develops the most delicate phase of its cycle which is that of the enlargement of the tubers. During this period there should never be a lack of good humidity conditions in the soil. The most used irrigation systems are: furrow infiltration and sprinkling.
The production of seed tubers
The environment required for the production of seed tubers must be characterized by a cool climate with moderate temperatures throughout the cycle of the plant without alternating periods of rain and drought. This environment in Italy is found in particular in the mountains, where, however, the territorial decentralization and the reduced cultivation units significantly increase the production costs and the difficulties of preserving the tubers. This situation makes it difficult in Italy to extend the production of seed potatoes, making us largely indebted from abroad for the seed requirement.
Sprouted potato tubers (website photo)
Collection, production and conservation
The harvest of new potatoes is brought forward, for market reasons, to a stage where the periderm is not yet suberified and easily detaches by exerting tangential pressure on the tuber with the fingers.
For potatoes intended for fresh consumption or for industry, the tubers must ripen
complete. Simple indications to evaluate the reached maturation are the yellowing of the foliage and the consistency of the periderm, which must not detach, but be well suberified and impact resistant. In large crops, harvesting is mechanized, using simple excavating machines, which leave the tubers in rows in the field, which are subsequently picked up, or harvesting excavating machines. Harvesting should take place with not damp soil, not only because the operation is easier , but also to collect dry and clean tubers.
The unit yields can vary considerably in relation to the environment and culture conditions. In the best situations, they can rise to 400q / ha and above; but also a yield of 250 q / ha can be considered satisfactory.
Storage - The harvested potatoes are immediately placed on the market for fresh consumption only in the case
production out of season (early, leap) or early. The bulk of the production of
season is placed on the market, both for fresh consumption and industry, gradually for a
period of time that can extend up to 8-10 months: it is therefore very important to store potatoes appropriately for:
- limit weight loss;
- prevent both sprouting and the development of diseases;
- preserve the quality of the tubers: culinary for the potatoes for consumption, technological for those destined for industrial transformation.
Good conservation depends on the conditions of the storage room. The optimum storage temperature is 5-6 ° C. Lower temperatures have the effect of producing an excessive accumulation of soluble sugars (fructose, glucose), responsible for the "sweetening" of the tubers. Potatoes destined for consumption can undergo a treatment with anti-sprouting products (based on CICP) when the conservation has to be prolonged beyond 2-3 months with temperatures of 6 ° C or more.
Conservation warehouses must be well ventilated so as to allow the drying of the newly introduced tubers, favor the healing of the wounds received at the harvest, prevent the condensation of water on their surface.
Excessive light intensity can green cortical states. This greening is a serious drawback for table tubers (bitter taste, presence of solanine), but it can be useful for seed tubers.
Adversity and pests
Late frosts can compromise the damage to the crop when they occur after the emergence of the plants: drought is equally harmful, especially if it occurs in the initial stages of plant development or during the redness of the tubers. Hail can cause severe mutilations on the vegetative apparatus; the reflections on production, however, are more often of lesser extent than the appearance of the aerial part may appear. The unfavorable climatic conditions can have an indirect negative effect on production, as they favor the attack of parasites or diseases of different nature.
The most feared is the golden nematode (Heterodera rostochiensis) which can attack the plant in all phases of the cycle, destroying the product. The fight is based both on agronomic principles, adopting alternations in which the potato returns to the same plot at long intervals, and on genetic principles, using resistant varieties. Other parasitic nematodes of the plant, but of secondary importance belong to the gen. Meloidogyne (root knot nematodes).
- Downy mildew of the potato (Phitophthora infestans): occurs both on the leaves and on the tubers; some varieties are more resistant; it can be easily controlled with suitable treatments (e.g. copper products).
- Dry gangrene (Fusarium spp.): Affects the tuber especially during the conservation period.
Powdery scabies (Spongospora subterranea), common scabies (Actinomuces scabies) and silvery scabies (Helminthosporium atrovirens): they affect the tuber in the epidermal area, causing the appearance of pustules.
- Black mange or cancer (Synchytrium endoticum): causes necrosis especially in the internal tissues of the tuber.
- Bacteriosis of the potato (Pectobacterium carotovorum var. Atrosepticum).
- Alternariosis (Alternaria solani).
- Trachemicosis (Fusarium spp. And Verticillium spp.) Affects the internal tissues of juvenile stems.
The potato is one of the agrarian plants most affected by virosis. Several viroses can be simultaneously present on the same plant.
- Rolling up;
- Virus y;
- Virus x;
- Virus A;
- Virus M;
- Virus S;
- Aucuba mosaic.
Mole cricket (Gryllotalpa gryllotalpa), some species of aphids (e.g. Mtzodes persicae), beetle (Melolontha melolontha), apron (Agriotes lineatus), Colorado beetle (Leptinotarsa decemlineata). Suitable and specific control systems are possible against these insects.
Summary from Herbaceous crops - Remigio Baldoni, Luigi Giardini - Pàtron Editore