Strobilurin Effects on Nitrogen Use Efficiency for the Yield and Protein in Durum Wheat Grown under Rainfed Mediterranean Conditions

In wheat, the increase in nitrogen use efficiency (NUE) and optimization of the nitrogen doses to be used are both very important aspects for improving sustainable and productive agriculture. The aim of this study was to investigate, under rainfed Mediterranean conditions, the influence of strobilurin treatment and N fertilization on durum wheat N use efficiency for yield (NUEy) and protein (NUEp) and on the contribution of their components, nitrogen uptake efficiency (UPE) and nitrogen utilization efficiency (NUtE). Two durum wheat cultivars (Saragolla and Sfinge) were grown for two years in field conditions under five nitrogen treatments (60 kg ha−1 N60; 90 and 120 kg ha−1 given two and three times; N90, N90T3, N120 and N120T3) comparing a control without strobilurin treatment (ST0) and one application of strobilurin (STaz). In Sfinge, STaz caused a decrease in UPE and NUEp and an increase in NUtE and NUEy. In Saragolla, the opposite behavior was observed. Moreover, strobilurin positively affected the contribution of UPE and negatively that of NUtE to NUEy only in Saragolla. Furthermore, strobilurin determined higher NUEy and NUEp values under most of the N treatments adopted in the drier year. With this study, we supported the hypothesis that in Mediterranean conditions, the possibility of reducing N rate application from 120 to 90 kg ha−1 with a strobilurin-based treatment, even in the absence of fungal diseases, could represent a useful agronomic strategy for durum wheat grown under drought conditions as those predicted under the ongoing climate change.