Effects of a new biostimulant on vegetational indexes, yield and quality in common wheat

Wheat is the most cultivated crop in the world with a high nitrogen requirement. In order to reduce nitrogen leaching and abiotic stress risks related to climate change, new agronomic practices are currently being developed to maximise nitrogen use efficiency and crop yield and quality. Among these, the use of biostimulants is spreading worldwide in many crops and may replace late season foliar nitrogen supply. In this thesis, a new biostimulant obtained from sage and husk rice extracts was applied as foliar spraying in three common wheat varieties (i.e. var. Bologna, Vivendo and Solehio) at flowering stage and its effects were compared with untreated controls and two benchmark commercial biostimulants obtained from protein hydrolisates. The trial was arranged at the Experimental farm of the University of Padova at Legnaro in 2020-21, following a completely randomised block design with 3 replicates. After application of biostimulants, the canopy greenness was monitored during the grain filling by weekly detection of NDVI and SPAD, while at harvest grain yield was quantified through a plot combine harvester. Quality and bread-making parameters were measured by NIRS and the Chopin alveograph, respectively. Similarly to the two benchmarks, the new biostimulant significantly delayed leaf senescence that is commonly observed with the approach of ripening. Compared to the untreated controls, higher NDVI values were found with all the three biostimulants for var. Bologna, and the maintenance of high values of leaf chlorophyll content (SPAD values) for longer time in var. Vivendo and Solehio, especially with the new biostimulant. The maintenance of greenness by the crop for a longer period than the control led to significant increases in protein content, wet gluten and the Zeleny index, with more marked improvements in var. Bologna compared to Solehio and Vivendo. The results on yield were contrasting, with a slight decrease in Bologna and Vivendo (more protein-rich varieties) and a slight increase in Solehio, regardless of the type of biostimulant applied. It is believed that yield response was greatly affected by the particular climatic conditions in 2021, with abundant rains and low temperatures in April and May, suggesting the need to repeat the trial for a second year. The qualitative improvements obtained by the biostimulants linked to proteins and gluten did not translate into evident variations in the rheological quality of the doughs. From the nutraceutical point of view, the possible increase in some varieties of the content of antioxidants (phenolic acids) in flour is interesting, in particular with one of the two benchmarks.