Effect of Plant Density, Rate and Split Application of Nitrogen Fertilizer on Quality Characteristics and Nitrogen Use Efficiency of Safflower under Weed Competition

In order to evaluation of plant density, rate and method of nitrogen fertilizer split application on quality characteristics and nitrogen use efficiency of safflower (Sofeh variety) under weed competition a field experiment was carried out in field research Yasouj University in 2013. This experiment was a factorial based on randomized complete block design with three replications. First factor was a two levels plant density (20 and 40 plants m-2) and second factor was nitrogen rate application on nine levels. That included; non nitrogen application and 75 and 150 kgN ha-1 nitrogen application that both used with four split method. Split methods were included; S1 (%50 in pre planting stage - %50 in stem elongation stage), S2 (%25 in pre planting stage - %75 in stem elongation stage), S3 (%25 in pre planting stage - %50 in stem elongation stage -%25 in flowering stage) and S4 (%25 in pre planting stage - %25 in stem elongation stage - %25 in flowering stage). Also in this experiment, weed did not control. Results showed that whit increasing crop density, oil yield and protein grain yield increased by 20 percent and nitrogen utilization efficiency increased by 10 percent. The highest oil yield (50.25 g m-2) was obtained from 75 kg ha-1 nitrogen with three-stage split application (S4). Finally, results showed that increasing nitrogen fertilizer application decreased nitrogen utilization efficiency but three-stage split method application increased this trait