Response of Italian ryegrass seed crop to spring nitrogen application in the first harvest year

Italian ryegrass (Lolium multiflorum Lam.) cv. Tetraflorum was sown with different nitrogen application rates and it was tested under the agroecological conditions of Western Serbia. Four-year field experiments were carried out from 2002 to 2006 and the biometric characteristics of generative tillers, seed yield and shoot dry matter (herbage yield) were measured during the first production year. Italian ryegrass crop was established with four spring nitrogen application rates: 0, 50, 100 and 150 kg ha-1. Tiller length was not affected by nitrogen application, while two other tiller parameters were much more affected by the treatments. The maximum seed yield in the first production year varied among treatments depending on season conditions. Harvest characteristics were impacted by nitrogen application; however, there was an opposite impact in arid and humid weather conditions. The N application of 50 kg ha-1 was found to be the optimal for seed production in those conditions. Higher rates of N application (100 to 150 kg ha-1) had either no impact on seed yield, or decreased the yield of seed as a result of ryegrass lodging following seed shedding. Abundant shoot dry matter was obtained in some treatment variants, but there was no linear correlation between seed yield and yield components.Key words: Harvest characteristics, Italian ryegrass, nitrogen application, seed yield