The preparation of potatoes for the storage stage begins long before the products arrive at the store. About how to correctly conduct this work and what to pay special attention to, we talk with Stanislav Vladimirovich Maltsev, Doctor of Agricultural Sciences, Head of the Potato Storage and Processing Laboratory of the Federal Research Center of Potatoes. A.G. Lorkha.
- Stanislav Vladimirovich, let's start by choosing the right varieties. It is known that there are varieties that are more and less suitable for storage. Does this characteristic depend on the ripening period of the tubers? Is it possible to say that late-ripening varieties, for example, are more suitable for storage than early-ripening ones?
- Tubers of varieties of early ripeness groups accumulate less dry matter and starch during the growing season. Accordingly, they have a higher proportion of water, the evaporation of which during long-term storage accounts for a significant part of the natural loss of potato mass. In addition, earlier varieties are harvested earlier and are stored longer. Therefore, other things being equal, early and especially ultra-early varieties are characterized by a higher level of losses during storage. However, the keeping quality of potatoes also significantly depends on the duration of the natural dormancy of the tubers, which determines the onset of their germination and losses for sprouts. This indicator is directly related to varietal characteristics and does not depend on the ripeness group.
- Before planting potatoes, experts recommend doing soil tests to determine which elements are in sufficient quantities and which are lacking. What indicators should you pay special attention to if you plan to lay potatoes for storage?
- Knowledge of the agrochemical parameters of the soil is important for calculating the optimal doses of fertilizers for potatoes. Often, agricultural producers, striving to get rich yields, add too much nitrogen, because of this, by the time of harvest, the tubers turn out to be physiologically immature (with lower starch levels, which leads to a deterioration in taste; with an increased content of nitrates). In addition, these potatoes have a fragile skin that is prone to serious damage during harvesting. The consequence of this is a decrease in the keeping quality of tubers.
The optimal N: P: K ratio for potatoes is 1: 1-1,2: 1,2-1,5. It should be borne in mind that the relatively high content of phosphorus in the soil alone does not guarantee its high availability for plants, since it can be in a complex with iron and aluminum. On such soils, it is necessary to apply a sufficient amount of fresh phosphorus fertilizers. Currently, phosphated soils are present in many farms that use intensive methods of crop production, and for crop rotations saturated with potatoes, this is the most frequent phenomenon (without liming, acidity increases, the content of iron and aluminum increases, which strongly binds phosphorus and leads to phosphating).
- What elements should be included in the potato nutrition system during the season and in what periods?
- The most widespread in Russian farms was the method of fractional local application of mineral fertilizers: 2/3 when cutting ridges (or when planting, if Dutch technology is used) and 1/3 - in root feeding with inter-row cultivation two weeks after the emergence of seedlings (i.e. , for example, N60P60K90 + N30P30K45 according to the active substance). Potatoes respond well to irrigation, and if possible, watering (200 m3/ ha) is combined with the introduction of ammonium nitrate 5 kg / ha or micronutrient fertilizers (in the Central region of Russia, two to four irrigations are carried out in July-August, depending on weather conditions).
- What else is important to consider when growing potatoes, so that later they are well stored? How and when is it best to desiccate the foliage? At what temperature of air and soil is it recommended to harvest?
- Firstly, during the growing season, it is necessary to carry out timely treatment of plants with contact, systemic and translaminar preparations against late blight, alternaria, anthracnose and other fungal and bacterial diseases. The required number of treatments is at least five per season. Secondly, in order to avoid massive soil suffocation of tubers, the soil in the ridges and aisles must be kept clean and loose until harvesting. Thirdly, it is imperative to carry out pre-harvest removal of tops by chemical (raglon super 2,5 l / ha, dry wind 2,5 l / ha, basta 2,0 l / ha), by mechanical or combined methods, depending on the conditions and development of tops, at least 10-12 days before digging the tubers. Fourthly, cleaning should be carried out in a timely manner and at an air temperature of at least +10 °C, otherwise the percentage of mechanically damaged and affected by Fusarium rot tubers sharply increases. With a delay in harvesting and carrying it out at high soil moisture (which is especially characteristic of heavy loams), the tubers have an increased turgor, and the pulp cracks under the influence of mechanical stress, tears and darkening are formed. If harvesting is delayed before the onset of frost, the injury rate of tubers increases even more, since the pulp is in a tense state and loses its elasticity (especially in the case of a high dry matter content). Often, under such unfavorable conditions, part of the crop generally has to be left in the field, and tubers that can still be harvested have a high percentage of mechanical damage and, as a result, poor keeping quality.
- What are the necessary stages of post-harvest preparation? Many experts say that most of Russian farms do not pay sufficient attention to removing land from the general flow of products, they are not engaged in sorting and sizing tubers. Why is it dangerous? What percentage of land is acceptable for storage?
- Harvesting is followed by the technological stage of laying potatoes for storage. There are three technologies for bookmarking - in-line, transshipment and direct-flow.
Streaming - Harvested potatoes are sent to a sorting station to separate soil, impurities and calibrate into fractions with subsequent storage. Compared to other technologies, with this tubers receive the greatest amount of mechanical damage. Therefore, it should be used only in cases where: 1) the product is planned to be sold during the fall; 2) the potatoes harvested by the combine comes from the field with an admixture of soil of more than 25-30% and with plant residues; 3) the tubers are fully ripe, have a hardened peel and are not affected by diseases.
Transshipment - tubers are kept in temporary piles before storage or sorting at the point. The use of this technology is mandatory in case of significant damage to tubers by suffocation, late blight, wet rot, as well as in seasons when harvesting is carried out in cold and rainy weather, especially with combines on heavy soils.
Direct-flow - the potatoes coming from the field are immediately put into storage without autumn sorting. Depending on the conditions, it can be performed in two ways. If the soil admixture in the heap does not exceed 10-15%, and the content of small tubers up to 30 mm in size is insignificant, they are harvested according to the simplest scheme "combine - storage", that is, the potatoes from the combine are taken to the storage and unloaded into the hopper of the TZK-type 30/60, which stacks the tubers. If the volume of soil in the total product flow exceeds 20% and there are many small tubers, the potatoes coming from the combine are unloaded into a receiving hopper installed in front of the storage gate. The bunker is equipped with a heap cleaner, which separates the soil and small tubers, and the bulk of the potatoes is fed by a system of conveyors (conveyors) to the storage, where the beater is located. On conveyors, non-standard tubers, lumps, stones and other impurities are manually selected. Seed potatoes laid using this technology are stored until spring, and calibrated into fractions during pre-planting preparation.
The presence of an excess amount of land in the embankment of stored potatoes worsens the conditions for its ventilation, creates a reservoir for the accumulation of phytopathogenic microorganisms, and, of course, farms try to avoid this as much as possible. However, this does not always work if the harvesting is delayed for some reason, especially if the work is carried out on heavy loamy soils.
According to GOST 7176-201 “Food potatoes. Technical conditions "the presence of soil adhering to the tubers is not allowed for early potatoes, for late ones - no more than 1% of the mass fraction is allowed. According to GOST 33996-2016. "Seed potatoes and methods for determining the quality" allowed the presence of soil and impurities, no more than 2% by weight in the categories OS, ES, RS1-2.
- What stages does the "treatment period" include for potatoes? Is it always needed?
- In general, potato storage technology includes five main periods: drying (100-200 m3/ t per hour), therapeutic, cooling (0,5 °C per day), main and spring.
It is always recommended to carry out the treatment period, if possible, since it is necessary to heal the mechanical damage caused to the tubers during harvesting and transportation, and thereby ensures the preparation of potatoes for long-term storage. The duration of the treatment period depends on the air temperature: at 18-20 °From it lasts 14-16 days, at 14-16 °From - 20-25 days. At a temperature of 12 °From and below the processes of ripening and scarring of sections and scratches do not occur.
The most active healing of injuries (the formation of layers of suberinized cells and wound peridermis) occurs at a temperature of about 18 °C.
Potatoes in the storage are ventilated with warm humid recirculated (internal) air 5-6 times a day for 30 minutes with intervals of 3,5-4 hours. The storage gate and the supply and exhaust valves are kept closed. During the treatment period, the relative humidity of the air (RH) is maintained at a level of 90-95% by adding a minimum amount of cold outside air to the internal air of the potato storage, for example, at night. Installation of an artificial humidifier in the air duct behind the fan is more efficient. A decrease in air humidity below 80% during the treatment period is unacceptable, since it contributes to a large evaporation of moisture from the tissues of the tubers.
During the treatment period, to prevent the formation of dry rot in places of mechanical damage to tubers (fungal diseases), it is recommended to treat potatoes with the help of active ventilation with a smoke preparation with the active ingredient thiabendazole (for example, "Vist" with a drug consumption of 8-10 g / t).
- Do I need to carry out a tuber analysis when it comes to ware potatoes?
- Yes, since the technology of storing potatoes largely depends on the initial quality of the tubers, which is precisely determined by the tuber analysis. Depending on the quality of the laid tubers and the incidence of their diseases, a decision is made on the intensity and duration of ventilation during the drying period, the storage temperature during the main period, as well as the possible maximum storage time for certain batches of potatoes and the optimal timing of their sale.