The assumption of this study was that in-season trends in the calcium concentration (Cac)  in potato organs allow one to identify the source of this nutrient for the growing tubers. This hypothesis was tested based on the data from field experiments (2006-2008), with sequentially added nutrients (Absolute control - AC, NP, NPK, NPKS, and NPKSMg). The Ca concentration (Cac) was measured in potato vines, stolons + roots, and three fractions of potato tubers. Potato plants were periodically harvested in 10-day sequences, starting from BBCH 33 until maturity. The tuber yield, averaged over fertilization treatments, was 33.4, 53.7, and 41.6 t·ha-1 in 2006, 2007, and 2008, respectively. The Cac in-season trends, regardless of the potato part, were governed by the weather and only slightly modified by the applied fertilizers. The Cac in potato organs, averaged over the growth season, was in the order: vines > stolons + roots > tubers. The high Cac in potato vines between 89 and 110 DAP, as recorded in 2007, can be treated as the prerequisite of high potato yield. The Cac status in potato vines on 99 DAP can be used as the yield predictor. The Cac maxima, revealed earlier or later during the potato growth period, as compared to 2007, resulted in the tuber yield decline. The Cac in the large-size potato tubers showed a progressive increase in accordance with the phases of potato tuber maturation. The main sources of Ca for the large-size tubers were other potato parts. The Cac increase in this potato fraction coincided with its simultaneous drop in the other potato organs, like shoots, stolons, and roots. Intensively expanding tubers created a strong sink for calcium, thus decreasing its concentration in tubers of the smaller size.  

25.1.2020