Optimising durum wheat cultivation in North Italy: understanding the effects of site-specific fertilization on yield and protein content

Variable rate fertilization and precision harvesting could increase the potential for meeting durum wheat quality standards. Field spatial distribution of yield and protein content, and their interactions with soil properties and N fertilization were evaluated in an experiment on durum wheat in North Italy in 2011 and 2012. Variable rate fertilization was adopted in three management zones (MZs) with increasing soil fertility, and a foliar N was applied at flowering to investigate differences in protein quantity and quality. During the crop cycle, changes in crop biomass and N status were monitored through NDVI measurement, and grain was sampled in each MZ and gluten proteins extracted at harvest. Spatial variability of yield and protein content was mainly driven by soil texture and base fertilization in both the years, while foliar fertilization was not efficient in enhancing grain protein content. Variable rate fertilization partially mitigated the weather impact; however, unpredictable weather conditions resulted in low N use efficiency. High N rates were confirmed to provide high protein levels and enhance gluten proteins technological quality, but with a risk for the environment. The marked spatial variability in grain quality in terms of total protein and gluten protein content, and the ratio between glutenin/gliadin and high and low-molecular weight glutenin sub-units, suggested the implementation of zone harvesting as a strategy to exploit the positive interaction between grain quality and soil fertility.