The aim of our study was to evaluate the effects of nitrogen (N) and sulphur (S) fertilizer on harvest index (HI), agronomic efficiency (AE), physiological efficiency (PE), utilization (U), and final efficiency index (EFI). We conducted a field experiment (2009-11) in southeastern Poland on Cambisols (WRB 2014). The experiment included two variables: N fertilization (0, 40, 80, and 120 kg/ha) and S fertilization (0 and 50 kg/ha).
The experiment showed the positive effect of N and S fertilization on grain and straw yields of spring wheat cv. Tybalt, with the highest yield obtained in the case of the application of 120 kg N ha^-1 (grain 5.59 t ha^-1, straw 8.00 t ha^-1). S fertilization increased grain yield by 3.58% and straw by 6.16%. Although N and S fertilization increased content and uptake of N and S in DM, they decreased significantly on the harvest index of N and S (HI_N, HI_S). On average, HI_N was 76.41% and HI_S was 45.87%. Among the tested combinations, the highest agronomic efficiency of N (AE_N), agronomic efficiency of S (AE_S), physiological efficiency of N (PE_N), physiological efficiency of S (PE_S), utilization of N (U_N), and utilization of S (U_S) as well the best final efficiency of N and S (EFI_N, EFI_S) were noted for the object where N application increased to 80 kg ha^-1 with the addition of 50 kg S ha^-1. This combination should be recommended for use in the practice of spring wheat fertilization with N and S. Increasing the rate of N fertilizer to 120 kg ha^-1 caused a reduction in the utilization of N (U_N), and the addition of S to this level of N caused a drop in its utilization by the grain. In conclusion, S fertilization is necessary in the conditions of negative S balance in the cultivated soils.