Effect of Different Levels of Nitrogen Application on Green Yield and Nutritive Value of Forage Sorghum (Sorghum bicolor (L.) Moench)

Abstract

     A field experiment was conducted from June to December in 2013 at Viet Nam National 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 kgP2O5 and 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 of nitrogen 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 lipids increased 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 increased nitrogen application and concurrent rise in HCN 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 can be applied for later cuttings of OPV cultivars.