Date Received: 31-03-2015 / Date Accepted: 21-04-2015
A field experiment was conducted from June to December in 2013 at Viet NamNational University of Agriculture to evaluate effect of four levels of nitrogen application (0 kgN, 120 kgN, 180 kgN, and 240 kgN per ha at a constant basal fertilizer of 120 kgP2O5and 120 kgK2O per ha) on growth, green fodder yield, and nutritive value of two sorghum cultivars, OPV21 and OPV88. Green yield and its related to parameters as well as nutritive value were determined at three cuttings: first cutting (90 days after sowing), second cutting (45 days after first cutting), and third cutting (45 days after second cutting). The obtained results showed that increase ofnitrogen level from 120 kgN to 180 kgN per ha did not lead to increased green yield. However, nutritive parameters,such as dry matter, total minerals, crude protein, and lipidsincreased while concentration of HCN decreased. At the second and third cutting, both of green yield and crop growth rate of OPV21 cultivar increased significantly with increasednitrogen applicationand concurrent rise inHCN concentration.The experiment suggested that the nitrogen level of 120 kg per ha should be applied for first cutting, whereas 180 kgN to 240 kgN per ha canbe appliedfor later cuttingsof OPV cultivars.
