The effect of nitrogen fertilization on forage yield and quality in some italian ryegrass (Lolium multiflorum Lam.) varieties

This study was carried out as a field trial in the vegetation period of 2017-2018, at the Mustafa Kemal University Telkaliş Research and Application Center (Reyhanlı/Hatay) under the ecological conditions of Hatay-Turkey. The field trial was set up 3 repetitions according to randomized split block experimental design. Accordingly, there were 5 different nitrogen doses [0 (control), 5, 10, 15 and 20 kg/da)] in the main plot and 3 different Italian ryegrass varieties (Hellene, Trinova and Devis) in the sub-plot. In order to determine the effect of different N doses on yield and quality of perennial ryegrass varieties; plant height, stem diameter, fresh forage yield, dry forage yield, crude protein yield, rate of crude protein, crude ash content, Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF) contents and Relative Feed Value (RFV) were examined. Although the effect of nitrogen doses on plant height was found to be insignificant, increasing nitrogen dose caused an increase in plant height of cultivars. In addition, an increase in fresh and dry forage yields were observed due to the increased nitrogen doses. Crude protein yields and crude protein contents increased with increasing nitrogen doses as well, and the highest values were reached with a dose of 15 kg/da N application. However, the stem diameter of the varieties was not affected by nitrogen fertilization. It has been also determined that nitrogenous fertilizers have no effect on the crude ash contents, NDF and ADF contents, and RFV values of the Italian ryegrass varieties. It has been concluded from research data that nitrogen fertilizers increase yield and quality of the Italian ryegrass up to a certain level, but higher nitrogen fertilizer doses (especially N dose at 20 kg/da) decrease the feed yield and quality. Therefore, 5-10 kg/da N dose can be recommended in Italian ryegrass production under Hatay/Turkey ecological conditions also by considering economic reasons. Devis cv. was more superior than others in terms of many investigated traits. Trinova variety can be the second choice for the region. However, the Hellen variety came into prominence in terms of RFV.