Effect of late-season nitrogen fertilization on grain yield and on flour rheological quality and stability in common wheat, under different production situations

The increasing demand for a high and homogeneous technological quality of common wheat (Triticum aestivum L.) points out the necessity of improving wheat with by a higher protein (GPC) and gluten content, strength of dough (W) and dough stability. Among the current crop practices, late-season nitrogen (N) fertilization, from heading to flowering, is generally considered the practice that has the most effects on the storage proteins and technological quality of the grain. In order to explore the influence late-season N application can have on the dough properties and on the formation of homogeneous lots in more detail, a research was set up between 2007 and 2013, over 6 growing seasons at different sites in North West Italy using the Bologna cultivar in each of the trials. Three different late-season N fertilization strategies were compared: T1, control without a late distribution of N; T2, foliar N fertilization at flowering; T3, top-dress granular soil fertilization at the beginning of heading. A randomized complete block experimental design with four replicates was adopted. The grain yield, GPC, W and P/L indexes were analyzed. Moreover, the rheological and enzymatic properties of the samples were studied using a Mixolab® analyser (Chòpin Technologies, Paris, France). Grain yield was found to be unaffected by the fertilization treatments, while the late N application (T2, T3) significantly increased GPC. Only the granular N fertilization (T3) increased the W index compared to T1, while the P/L index was not affected by any of the fertilization strategies. Furthermore, the T3 strategy was always more effective in reducing the variability of the W index than the T2 and the T1 strategies. Water absorption and dough development time were higher in T3, than in T1, while intermediate results were reached for T2. The effect of late-season N fertilization was also significant on the starch behaviour of the dough, as an increase in starch gelatinization and retrogradation was observed. In short, the top-dress granular N fertilizer applied at the beginning of heading (T3) led to a more constant increase in GPC and flour rheological quality than the foliar application. Moreover, the adoption of this fertilization strategy resulted in a reduction in qualitative variability under different environmental and soil conditions.