Potassium fertilization as a driver of sustainable management of nitrogen in potato (Solanum tuberosum L.)

The objectives of the present study were to assess and demonstrate the role of potassium fertilizer management on nitrogen use efficiency (NUE), and to select the most suitable set of NUE indicators. A series of six field experiments was conducted during 2009-2014. A principal trial factor was crop rotation (CR), potatoes - winter wheat - winter barley (1st CR/ lupine - cover crop/2nd CR). The experimental design was composed of four K rates (0, 80, 160, 240 kg K2O ha(-1))and two N rates (120, 160 kg N ha(-1)). The marketable yield (MY) ranged from 20 to 49 Mg ha(-1). The amount of K in tubers at harvest (K-a) was significantly associated with the MY. K-a, largely governed by the interaction between CR and K rate, was also linked to Partial Factor Productivity of fertilizer nitrogen (PFPN) and Agronomic Nitrogen Efficiency (ANE). The results suggest that the K rate should be oriented to the realization of a specific production strategy, depending on environmental factors (water shortage), and N use efficiency. It was documented that increased K-a might be a crucial factor for controlling N productivity, subsequently decreasing its rates. At the optimum K fertilizer rate, N rates can be significantly reduced.