Nitrogen fertilization management and seeding density differently affect net blotch incidence and grain yield in one two-row and one six-row cultivar of barley

A two-year field experiment was carried out on barley (Hordeum vulgare L.) to test the effect of cultivar, N fertilization management and seeding density on crop growth, net blotch (NB) disease occurrence and yield. The three variables were factorially combined in a split-split-plot design as follows: 1) two barley cultivars, one tworow (H. v. distichum, cv Callas) and one six-row (H. v. hexastichum, cv Azzurro); 2) four N application schedules differing for rates and/or timing of N supply: unfertilized control; fertilized with 35 kg ha-1 of N at BBCH29 plus 30 kg ha-1 of N at BBCH31; fertilized with 70 kg ha-1 of N at BBCH29 plus 60 kg ha-1 of N at BBCH31; fertilized with 130 kg ha-1 of N simultaneously at BBCH31; 3) four seeding densities: 100, 200, 400 and 800 viable seeds m2. The three variables affected crop growth and NB occurrence resulting in different grain yield and quality. Results varied with the seasonal trend, in particular with rainfall regime and air temperature, for their possible effect on soil N dynamics and the presence of NB, which resulted in different source capacity, and for their effect on grain setting and filling, i.e., the sink capacity. Both N fertilization and seeding density increased NB pressure, with seeding density affecting the disease even under unfavourable weather conditions for NB development. At the maximum N fertilization rate, delaying N application helped limit plant height and the related risk of lodging, as well as NB symptoms, resulting in greater hectolitre weight and protein content together with no appreciable decrease of grain yield, provided seeding density was close to optimal (i.e., 400 seeds m-2) or higher.