Effects of nitrogen and phosphorus fertilizers on nutritive value of safflower forage and silage

The aim of this study was to determine the effects of ensiling and using of fertilizers nitrogen and phosphorus on chemical composition and ruminal DM degradability of safflower plant (Carthamustinctorius L.). The safflower plant was cultivated at December 2009، and harvested at June 2010 in flowering stage، chopped to 3-5 cm particles and then ensiled in the laboratory silos for 60 days. The experimental treatments were: unfertilized forage (control)، phosphorus fertilized forage (100 kg per ha)، nitrogen fertilized forage (300 kg per ha)، nitrogen and phosphorus fertilized forage (300 kg N and 100 kg P per ha)، silage produced from unfertilized forage، silage produced from phosphorus fertilized forage (100 kg per ha)، silage produced from nitrogen fertilized forage (300 kg per ha)، silage produced from nitrogen and phosphorus fertilized forage (300 kg N and 100 kg P per ha). Chemical composition، DM degradability and digestibility were determined using standard methods. Nitrogen and P fertilizers reduced the NDF and ADF and increased the ash، Ca and P contents of plant (P<0. 05). The N fertilizer increased the CP، NPN and buffer soluble protein and decreased the ADIN content of plant (P<0. 05). The N and P fertilizers and ensiling increased a and c fractions and ruminal effective degradability of DM (P<0. 05). Applying the N and P fertilizers and ensiling also increased the gas production parameters including b and c fractions and ME and OMD content of plant. Based on resultys of this research، using of safflower silage produced from nitrogen and phosphorus fertilized forage compard to unfertilized forage is recommended. Keywords chemical composition; ruminal degradability; gas production; safflower; forage; silage