Feeding affects the development of potato farming, the formation and growth of tubers, as well as their final quality. The nutritional needs of the crop, however, change depending on the planting season, the development stage and the soil condition.
At this time there are spring plantings that are already in advanced stages and newer summer plantings, some of which are at the beginning of the wart. This differentiation determines which interventions can still be carried out and with what safety margins.
For the possibilities of intervention at every stage, the most frequent errors in lubrication and factors affecting the utilization of nutrients, the experienced agricultural worker Elias Eleftheriadis, a former member of the Department of Quality and Phytosanitary Control of Drama, speaks to Agritype.
Limited scope for intervention in advanced spring plantings
In spring potato crops already at an advanced stage, the possibilities for intervention are now very limited. «The procedures on the potato are practically complete», Mr Eleftheriadis points out that certain intervention margins may still exist in late plantings or in varieties with a large biological cycle, always depending on the area and the exact development stage.
In such cases targeted potassium and magnesium applications, as well as calcium nitrate hydrolipsis or water soluble nitrogen fertilisers may be considered, but only in very low doses.
More attention is needed when a large number of tubers are formed, there is a weakness for their magnification and there are not sufficient nitrogen reserves in the soil. In such a case additional nitrogen can be considered. «This must be done with very great method», points out, explaining that it is necessary to have an image of soil stocks before any application. Excessive administration of nitrogen at this stage may cause deformities in tubers, frames and lacerations.
Therefore, in advanced spring plantings there is no room for generalised applications. Each additional operation should be based on a real need and should be performed accurately in terms of dose and time of application.
The principle of wartling in summer plantings is crucial
More possibilities of feeding management exist in summer plantings that are at the beginning of the wart, when the formation of tubers begins and the needs of the crop gradually increase in available nutrients.
Where deficiencies are detected, cross-sheet data applications such as boron and magnesium may be carried out. Phosphorus is also of particular importance, as according to Mr Eleftheriadis, it has a significant influence on the process of warring. In the event of an identified deficiency, cross-sheet applications of appropriate phosphate-soluble fertilisers may be considered.
In very poor soils, which cannot contain sufficient amounts of nutrients and function as «storage» for cultivation, the farmer refers to a practice of partial application of basic lubrication. In particular, 70% of basic lubrication is applied during planting, while the remaining 30% is administered at the beginning of tuberculosis. This practice seeks to ensure that nutrients are available during the increased needs of the potato.
The maximum requirements of the crop start, as it says, from the stage at which the potato «Makes the so-called knee», i.e. since the growth of tubers begins. «We want at that time to have the maximum possible concentration of available nutrients on the ground.», points out, in order to properly support tuberculosis, growth and accumulation of dry matter in tubers.
Rather, the excessive presence of nutrients in the early stages, and particularly nitrogen, is not desirable. Increased nitrogen lubrication leads to excessive growth of the leaf mass, favours peron seed infestations that are then difficult to contain and at the same time seriously impedes tuberculosis, becoming, according to Mr.Eleftheriadis, one of the most important errors in potato farming.
As regards the overall classification of potato requirements, the agronomist first places potassium and then magnesium and calcium. The uncle follows, and the boron is especially important. Mr Eleftheriadis refers to approximately 30 potassium units, 8 calcium units and a corresponding amount of magnesium, while pointing to the great importance of potassium for cultivation. These quantities are not a single recommendation for each potato crop, as the final application must be adapted to the soil condition, the development stage and the actual needs of the plantation. In the case of boron, where soil deficiency is found, cross-leaf applications during the early stages of the plantation may, according to him, be particularly effective.
Soil analysis and leaflet do not function independently
The rational management of nutrition requires knowledge of the condition of the soil, but also monitoring how cultivation responds to applications. Soil analysis is a key starting point, as it gives an initial picture of the stocks and condition of the soil. However, as Mr Eleftheriadis points out, «soil analysis is a static image of soil status», as it cannot fully deliver parameters such as the mobility of nutrients and the condition of microbiota or soil microflora.
Thus, it is possible that an element is in sufficient quantity on the soil, but is not effectively exploited by the plant. This may be due to competition between the elements, their low mobility or factors related to the biological state of the soil.
At this point, leaflet diagnostics are of particular value, as it shows whether applications designed on the basis of soil analysis have finally had the expected effect on cultivation. Based on the results of the leaflet, corrective movements can be planned for the next growing seasons. At the same time, if the plantation stage permits it, there may still be room for corrective interventions by means of cross-leaf applications or water lubrication.
The effectiveness of feeding, however, also affects the conditions prevailing in the field. A critical parameter is the condition of the soil and especially the presence of water. The conditions of increased territorial humidity can cause reducing phenomena, influence the oxygenation of the root system and alter the mobility and absorption of nitrogen and other nutrients.
The effect of temperature is important. High temperatures change nitrogen mobility and affect the absorption of other elements, which must be taken into account when assessing the nutrient status of the crop.
Παράλληλα, ιδιαίτερη σημασία έχει η σχέση μεταξύ των κατιόντων. Το κάλιο, ως μονοσθενές κατιόν, και το μαγνήσιο και το ασβέστιο, ως δισθενή κατιόντα, πρέπει να βρίσκονται σε ισορροπημένες αναλογίες. Μια μη ισορροπημένη σχέση μεταξύ τους μπορεί να προκαλέσει ανταγωνισμούς και να παρεμποδίσει την απορρόφηση κάποιου στοιχείου, ακόμη και αν αυτό υπάρχει στο έδαφος σε επαρκή ποσότητα.
Τι δείχνουν τα φύλλα και ποια λάθη πρέπει να αποφεύγονται
Πέρα από τις αναλύσεις, η εικόνα των φυτών στο χωράφι μπορεί να δώσει ενδείξεις για πιθανές ελλείψεις, χωρίς όμως τα ορατά συμπτώματα να πρέπει να αξιολογούνται αποσπασματικά. Η έλλειψη φωσφόρου μπορεί να εκδηλωθεί με ιώδη ή ανθοκυανικό χρωματισμό των φύλλων. Τα συμπτώματα εμφανίζονται συχνότερα στα αρχικά στάδια της φυτείας, ιδιαίτερα όταν επικρατούν χαμηλές θερμοκρασίες. Στην περίπτωση του αζώτου, χαρακτηριστική είναι η γενική καχεξία ή χλώρωση της καλλιέργειας. Οι ελλείψεις καλίου και μαγνησίου εμφανίζουν ορισμένες ομοιότητες και εκδηλώνονται κυρίως στα κατώτερα φύλλα με χλωρώσεις.
Αντίθετα, ελλείψεις μικροστοιχείων, όπως του σιδήρου και του μαγγανίου, μπορούν να γίνουν εμφανείς στα ανώτερα ή νεότερα φύλλα με χαρακτηριστικές χλωρώσεις. Στην περίπτωση του βορίου εμφανίζεται ο τυπικός σχηματισμός «ρόδακα», ένα σύμπτωμα γνωστό στους γεωπόνους, αλλά λιγότερο αναγνωρίσιμο από τους παραγωγούς.
Παρότι τα συμπτώματα μπορούν να αποτελέσουν χρήσιμη ένδειξη, η τελική αξιολόγηση πρέπει να συνδυάζεται με τη συνολική εικόνα της φυτείας και, όπου είναι δυνατόν, με τα αποτελέσματα των αναλύσεων. Σε επίπεδο εφαρμογών, ο κ. Ελευθεριάδης επισημαίνει ότι ιδιαίτερα οι νεότεροι ή λιγότερο έμπειροι καλλιεργητές της πατάτας οδηγούνται συχνά σε υπερβάσεις αζώτου, αλλά και σε υπερβολικές φωσφορούχες λιπάνσεις.
Προβλήματα παρατηρούνται και στη διαχείριση των μικροστοιχείων. Αν και γίνονται διαφυλλικές εφαρμογές, αυτές δεν πραγματοποιούνται πάντοτε με συγκεκριμένο σχεδιασμό και μεθοδικότητα. «Πρέπει να ξέρεις τι κάνεις και να έχεις κάτι σοβαρό στα χέρια σου», τονίζει, επισημαίνοντας ότι οι εφαρμογές δεν πρέπει να γίνονται μηχανικά, αλλά να βασίζονται σε πραγματικά δεδομένα της καλλιέργειας. Όπως χαρακτηριστικά αναφέρει, «πολλές φορές οι υπερβάσεις μπορεί να είναι απλές υπερβάσεις, μπορεί όμως να εξελιχθούν και σε υπερβολές».
