Abstract

One of the challenges of potato (Solanum tuberosum L.) production is to minimize phosphorus (P) fertilization without negatively affecting the yield progress. Therefore, critical P dilution curves [P-c = a(c)W(-b); where P-c is the critical P concentration (%); a(c) is the critical plant P concentration (%) for a total dry matter (DM) biomass of 1 Mg ha(-1); W is the total DM biomass expressed in Mg ha(-1); and coefficient b is dimensionless and represents the ratio between the relative decline in plant P concentration and the relative crop growth rate] have been developed recently to improve P fertilization management in potatoes. The aim of this study was to test critical P dilution curves for potato cultivated in Sao Paulo State, southeastern Brazil. Nine field experiments were conducted in Oxisols with P-resin values ranging from 8 to 70 mg dm(-3) (very low to high). In each experiment, treatments were different P rates (ranging from 0 to 448 kg P ha(-1)) or the combination of different cultivars and P rates. Wide ranges in tuber DM yield (0.7-7.9 Mg ha(-1)) and plant P concentration (0.13-0.36 %) were observed before vine killing in response to P rates, cultivars, and site-years. Tuber DM yields were related to total DM biomass (R-2 = 0.98), while P uptake was related to both total DM biomass and total plant P concentration (p < 0.01). Relative tuber DM yields at harvest were closely related to P nutrition index (PNI) (p < 0.01, R-2 = 0.82) calculated with the critical P dilution curve previously reported for potato under higher yielding environments. These results validate the critical P dilution curve (P-c = 0.391W(-0.304)) as a useful diagnostic tool for improving the P fertilization of potato crops systems in the tropical region of Brazil.