The Effect of Sulfur Carriers on Nitrogen Use Efficiency in Potatoes—A Case Study

Abstract

The use of sulfur is an important factor in potato production. At the beginning of this study, a hypothesis was put forward according to which sulfur carrier affects yield (TY) and nitrogen efficiency (EN). The three-year study was conducted in a two-factor system: (1) sulfur fertilization, SF (control—without S, elemental sulfur—S0, calcium sulfate—CS), and (2) nitrogen fertilization level, NF (0, 30, 60, 90, 120, and 150 kg N·ha−1). In addition to TY, the following EN indicators were analyzed: agronomical efficiency (EA), physiological efficiency (EPh), partial factor productivity (PFP), and recovery (R). For both sources of sulfur, an increase in TY was confirmed. After applying CS, the optimum for the maximum yield was 106 kg N·ha−1, while the application of S0 resulted in 134 kg N·ha−1. The impact of SF on the nitrogen economy decreased in the direction of EA = PFP > EF > R and depended on the sulfur carrier. A positive trend was found, associated with the increase in R under the influence of S0 and the clearly higher EPh after the application of CS. A particularly strong effect of CS on EA was evident in the range of lower nitrogen doses. The EN values depended on the meteorological conditions during the research years. The strongest variability was subject to EPh, which, as a result of SF, was significantly higher in relation to the control (without S) during the growing season, with an unfavorable distribution of precipitation. The application of CS reduced the unit nitrogen uptake (UU-N). Using path analysis, a direct relationship of Ca accumulation (controlled by N and S) with TY was demonstrated. The conducted research indicates a significant impact of sulfur fertilizers, related to TY and EN, especially visible under conditions of limited nitrogen supply.