Effects of nitrogen fertilizers on the yield of switchgrass in Kubuqi Sandland, northern China

Switchgrass (Panicum virgatum) is a warm-season plant, with high biomass, good wind-preventing and sand-fixing effect, and is a herbaceous bioenergy plant with good prospects for development.In order to introduce the switchgrass to Kubuqi Sandland of northern China, a switchgrass variety BL-1 was used as an experimental material to research the responses of the yield (biomass, crude protein yield, neutral detergent fiber yield, acid detergent fiber yield) of switchgrass in Kubuqi Sandland to the application of urea and ammonium sulfate. Urea and ammonium sulfate were carried out with four treatments of nitrogen application rate(0, 75, 150 and 225 kg/ha) and three duplicates for each treatment. Urea and ammonium sulfate were applied directly into the experimental plots at the seedling stage, tillering stage and jointing stage, with the amount of 1/5, 2/5 and 2/5 of nitrogen application rate, respectively. The plant height, stem diameter, leaf area and aboveground biomass were measured at the jointing stage, booting stage and early flowering stage of switchgrass. The results showed that the application of urea and ammonium sulfate both could significantly increase the yield of switchgrass. The yield of switchgrass applied ammonium sulfate increased gradually with the increase of nitrogen application rate, while the yield applied urea increased first and then decreased, and the highest yield appeared at the nitrogen application rate of 150 kg/ha. There was no significant difference in the yield of switchgrass between urea and ammonium sulfate when the nitrogen application rate was 75 and 150 kg/ha. The yield of switchgrass applied ammonium sulfate was significantly higher than that applied urea when the nitrogen application rate was 225 kg/ha.The plant size and leaf area of switchgrass were important factors affecting the yield of switchgrass. The promotion of nitrogen fertilizer to the growth of switchgrass was the most obvious at jointing stage, to the leaf area of switchgrass was at booting stage, and to the rapidly increase production of switchgrass was in the early flowering stage. Compared with urea, ammonium sulfate was more conducive to the rapid promotion of switchgrass yield.