The assumption of this study was that the trends in phosphorus (P) concentrations in potato organs during the growing season can be used as indicators of the P supply to plants, and therefore they can be used as a tool to predict tuber yield. This hypothesis was validated based on the data from field experiments (2006-2008), with series of nutrients sequentially added (Absolute control - AC, NP, NPK, NPKS, and NPKSMg) to potatoes. The P concentration (Pc) was measured in potato vines, stolon + roots, and three fractions of potato tubers. The plants were periodically harvested in 10-day intervals, 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. Trends of Pc, regardless of potato part, significantly depended on weather conditions in particular seasons. The fertilizer P applied together with nitrogen resulted in the Pc increase in potato parts, but without a significant impact on the yield of tubers. Trends in Pc developed for vines and stolons + roots fairly well reflect the disturbance of the P supply to potato. No trend in Pc emerged in 2007, a year with an ample supply of water.. This finding clearly informs us that P was not a factor limiting potato growth. The Pc trends in small-size potato tubers showed that the later the date of the optimum DAP for the Pcmax was, the higher yield of tubers was harvested. The quadratic regression models obtained for the small-, and medium-size tubers clearly demonstrate P shortage to these tuber fractions, following the DAP optimum. The same model, but for the large-size tubers, indicates the P dilution effect, which resulted from the excessive growth of tubers with respect to the amount of accumulated P. In consequence, the Pc in tubers was relatively low.  

24.3.2019