Seeding Density and Nitrogen Fertilization Effects on Agronomic Responses of Some Hybrid Barley Lines in a Mediterranean Environment

Over two cropping seasons, 2017/18 and 2018/19, an experimental trial was conducted in a typical cereal-growing environment of the Calabrian hills (southern Italy) to study seeding rate (D) and nitrogen fertilization (N) effects on two barley F1 hybrids (Zoo and Jallon) compared to those of a traditional variety (Lutece), assessing the bio-agronomic response. Barley hybrids, gradually introduced into the principal European countries starting in 2010 as winter forage, currently represent a significant part of the EU internal market. Productive performance was evaluated as grain yield for feed and total biomass for silage and/or biogas production. Research results pointed out the greater performance of barley hybrids compared to conventional varieties in terms of both grain and biomass production. On average, barley hybrids vigour mainly manifested itself through a high tillering and a greater number of ears m(-2) compared to those of the conventional variety (+24 and +23%, respectively). Furthermore, barley hybrids were characterized by a greater 1000-kernel weight and hectolitre weight than those of the Lutece variety (conventional variety). A significant increase in grain production was observed, increasing density from D-150 to D-225 rates (+35% and +33%, respectively) which was followed by a decrease in production shifting from D-225 to D-300 doses. A significant increase in biomass production was as well highlighted for the two hybrids, shifting from D-150 to D-225 rates (+26% and +27%, respectively). The applied nitrogen dose highlighted a different behaviour between the hybrids and the conventional variety; in particular, the lowest nitrogen dose (N-80) negatively influenced the Lutece variety both in terms of grain and biomass production (-9% and -16%, respectively) while the hybrids showed the best agronomic response even at the lowest dose. On average, with the N-80 dose, grain yield of Zoo and Jallon was greater than 20% and 16%, while with the N-120 dose grain yield was 9% and 7%, respectively. A similar behaviour was found for biomass yield. It should therefore be emphasized that barley hybrids possess high yielding capacities and that such higher grain production can be achieved in a Mediterranean environment by using a lower seed rate (approximately -25%) and a reduced nitrogen dose (approximately -33%) compared with those commonly applied to conventional varieties.