Optimizing Nitrogen Fertilization to Improve Qualitative Performances and Physiological and Yield Responses of Potato (Solanum tuberosum L.)

Potato is often produced by adopting high nitrogen (N) external inputs to maximize its yield, although the possible agronomic and qualitative benefits of a N over-fertilization to the crop are scarcely demonstrated. Therefore, our aim was to determine, over two years, the effect of three N fertilization rates (0, 140 and 280 kg ha(-1), referred to as N0, N140 and N280) simultaneously on the crop physiology, yield components, N use efficiency and tuber chemical composition of cv. Bellini. Throughout the field monitoring, our data highlighted that N140 provided an improvement of the crop physiology, as expressed in terms of leaf photosynthesis rate and Soil Plant Analysis Development (SPAD) readings, than the other N fertilization rates. In addition, regardless of year and as compared to N0 and N280, the supply of 140 kg N ha(-1) also ensured the highest yield and an intermediate value of the nitrogen use efficiency (59.1 t ha(-1) and 37.1 kg tuber dry weight kg N-1, respectively), together with nutritionally relevant tuber qualitative traits, i.e. high levels of dry matter, starch (by an enzymatic/spectrophotometric method), total polyphenols (by Folin-Ciocalteu assay) and ascorbic acid [by high-performance liquid chromatography (HPLC) analysis], and a low nitrate amount (by an ion-selective electrode method) (16.6%, 634-3.31-0.61 and 0.93 g kg(-1) of dry matter, respectively). Therefore, although a certain interaction between N fertilization rate and year was observed, our findings demonstrated that a conventional N fertilization rate (280 kg ha(-1)) is unnecessary from both agronomic and qualitative standpoints. This is of considerable importance in the perspective to both limit environmental pollution and improve growers' profits by limiting N external inputs to potato crops.