One of the indicators considered when choosing a variety is keeping quality. Besides the fact that potatoes need to be grown, they also need to be preserved.
What is keeping quality? This is the ability of potatoes to be stored for a certain time without significant weight loss, damage by phytopathogenic microorganisms and physiological disorders, deterioration of marketable, taste and seed qualities.
Storage of the potato crop is both the final stage of the growing season and, at the same time, its beginning - when it comes to future seed material.
In the process of breeding new varieties, along with yield, resistance to adverse weather conditions, diseases and pests, keeping quality is taken into account as one of the main criteria. The assessment of the keeping quality of tubers during storage is carried out on a 9-point scale, where 9 points is the highest point, very good; 6 - medium to good, 1 - very low. For example, Norika varieties have an average keeping quality score of 1 on a scale from 9 to 7, which is characterized as good keeping quality. These data help us understand how long the variety can be stored, how the potatoes lie, whether they are prone to germination - all this allows us to determine the optimal timing of product sales and, if necessary, adjust the storage regime. The characteristics of a particular variety are also of great importance. For example, the Inara variety has a score of 5 according to the keeping score system, while the variety is stable during storage, is not afraid of sprouts breaking off, tubers can germinate up to three times - this does not affect germination and yield, which is important when planting.
The keeping quality of tubers depends on a large number of factors: the genetic characteristics of the variety, the harvesting conditions, the correct storage (treatment period) and, of course, the storage mode itself.
Potatoes are a living organism with its own cycle, in which each stage is significant. Healthy planting material is the basis, then we need to grow it, get a good harvest, then carefully harvest it, store it, protect it from the development of diseases, germination, hypothermia, etc. Storage takes on average 7 months out of 12. Why is the storage period so important , besides the length of his term? At this stage, various physiological and biochemical processes take place in the potato tubers, the results of which affect the quality of the potato. For example, for chip varieties, the structure of sugars is very important in order to get beautiful tasty chips without spots when frying, and the desired indicators can be achieved only if the correct storage temperature is observed (8-10 ° C so that starch does not turn into reducing sugars, with the exception of varieties, capable of not changing the structure of sugars at + 4 ° C and maintaining the product quality necessary for the production of chips - this includes, for example, the Kibits variety).
Poor keeping quality during storage can be due to a number of reasons: mechanical damage to tubers, adverse weather conditions during the growing season and harvesting, violations during storage of potatoes, varietal characteristics.
One of the most important stages in the formation of potato keeping quality is harvesting. During preparation for it, it is necessary to monitor the condition of the tops and remove them in a timely manner (chemically or mechanically). These works are carried out when the leaves die off by 70% or 75% of the length of the stem without leaves (this applies to varieties of the mid-early group and later). In case of late blight, the tops are removed earlier.
We remove the tops in order to:
- to facilitate the harvesting process (the weight of the tops is 20-30 t / ha in the green state and 2-3 t / ha in the dry state);
- accelerate the physiological ripening of tubers + increase the strength of the peel to avoid mechanical damage;
- to reduce the risk of infection of tubers with an infection, including a viral one.
After the removal of the tops is completed, at least two to three weeks must pass before the start of harvesting for the skin of the tubers to become denser.
It should also be noted that in the production of seed potatoes, the newly grown tops are the main source of infection of plants with viruses. Methods of haulm removal, their sequence, preparations and application rates are selected individually for each specific case. It should be remembered that not all preparations are suitable for desiccation of seed potato tops, in addition, it should be borne in mind that on soils prone to lump formation, it is recommended to first use desiccants, and then carry out mechanical removal of the tops. On varieties with weak tops, mechanical removal can be dispensed with by desiccating in two sprays.
It is equally important to pay attention to the correct use of drugs, since a violation of the norms for application can cause darkening of the vascular ring (in this case, this is not a manifestation of the disease), decay of the stolon end of the tuber ("potato umbilical cord"), which subsequently leads to poor keeping quality and loss of commercial quality.
During the harvesting process, the grower must make every effort to reduce losses and injuries of tubers. A wide range of harvesting equipment (with the selection of the optimal technical means for a specific site) helps to accomplish this task; adjustment of harvesting and sorting machines; competent choice of working speed. It is important to establish the most accurate depth of burrowing of the ridges, at which the tubers will not be damaged and will not remain in the ground; take into account the presence of stones and clods in the product stream.
Ripe potatoes are harvested, with a hardened skin, preferably in dry weather.
Favorable conditions for harvesting potatoes are the absence of rain, the temperature of the soil and air is not lower than 10 ° C (when harvesting below 8 °, the percentage of mechanical damage increases), soil moisture is not higher than 70% of the total field moisture capacity.
And a few more words about the temperature regime. If the air temperature during harvesting and laying for storage is below 5 ° C, the natural healing process in the tubers does not occur, which leads to crop losses during storage. In addition, wet tubers harvested in cold weather do not have time to dry, which also contributes to a decrease in keeping quality.
Now about potato injuries. Harvesting unripe tubers with a fragile skin must be done with care, given that they are easily damaged. Before starting work, it is imperative to do control digging to understand the readiness of the potato. In addition, we must not forget that the varieties have different degrees of resistance to mechanical damage. More demanding for gentle cleaning, varieties with a high starch content. Large-tuberous and elongated varieties do not tolerate blows well. And for potato chips, the presence of bruises (the effects of blows) is the reason for recognizing the batch as not suitable for frying.
At the very stage of storage, several periods are allocated:
- treatment period;
- cooling period;
- the main storage period;
- heating before unloading / landing.
The process of drying potatoes after harvesting is of great importance in the formation of keeping quality. At this time, the ability of the potato to heal damage is realized. Also, the manufacturer gets the opportunity to correct the problems that arose during cleaning: for example, if the work was carried out in conditions of high humidity.
During the cooling period, the temperature in the storage is reduced by 1 ° C per day. This is done by ventilating with humid air (to preserve the turgor of the tubers). Too much ventilation or supply of dry air will lead to a loss of moisture in the tubers and a decrease in their mass, inhibit the healing process and can create a risk of dry rot. Airing should be stopped immediately if the top layer of the tubers becomes dry and appears to be covered with dust.
The duration of the treatment period depends on the weather conditions, the amount of moisture, the type of storage (shaft / containers) and the quality of the harvested potatoes. At the end of this phase, the first post-harvest tuber analysis is done to understand the health of the batch and take further steps to better preserve the produce.
During the cooling period, the temperature of the tubers gradually decreases to the optimum. And then, during the main storage period, the temperature and humidity conditions must be maintained at a constant level (without surges) by airing. In such conditions, the germination processes are inhibited in potatoes, although there are varieties that are prone to early awakening, therefore, for them, the "inhibition temperature" will need to be reduced (refers to seed potatoes).
Let us also touch upon the topic of storage diseases. The fight against them begins in the field, the health of the future party is laid in the growing season. Potatoes are very "fond" of diseases, they are an excellent environment for their development. During the storage period, diseases can progress. But! You can contain them if you pay attention to the number of damaged tubers in the total volume of production in a timely manner, correctly carry out the treatment period, and then monitor the temperature and humidity in the storage. The potato itself shows its "pain points", they only need to be understood correctly and try to reduce the negative consequences.
Congratulations to everyone with the beginning of the new season, we wish you good weather and a rich harvest of excellent quality!