Objective The study was carried out to explore the effects of different types of slow-release nitrogen fertilizers and different proportion with urea on yield and quality of forage maize, which would provide theoretical basis for green and high-quality cultivation of forage maize in Yunnan Province.

Method A field experiment was conducted with forage maize cultivar of'Qiaodan 6', and eight treatments were set: no nitrogen as the control, urea alone, slow-release nitrogen fertilizer with DMPP nitrification inhibitor and slow-release nitrogen fertilizer with γ-polyglutamic acid in combination with urea by ratios of 2 ∶ 8, 4 ∶ 6 and 6 ∶ 4, respectively The effects of different types of slow-release nitrogen fertilizers with urea at the same level of nitrogen application on the growth, yield and nitrogen utilization of forage maize were investigated.

Result The plant height, leaf area index, fresh yield and dry matter accumulation of forage maize under the treatment of slow-release nitrogen fertilizer containing DMPP and urea at the ratio of 6 ∶ 4 were significantly higher than those of other treatments, and the maximum fresh yield at harvest period was 8462 t/hm² and the maximum dry matter mass was 2535 t/hm² Compared with urea alone treatment, crude protein content, aboveground nitrogen accumulation amount and nitrogen utilization efficiency of A60 treatment increased by 4433%, 4884% and 6184%, respectively.

Conclusion The slow-release nitrogen fertilizer containing DMPP and urea at the ratio of 6 ∶ 4 significantly increased the plant height and leaf area index of forage maize compared with other treatments, which was beneficial to the accumulation of fresh yield and dry matter accumulation of forage maize, and increased its forage quality and nitrogen utilization Therefore, this ratio was the best ratio for green and high-quality cultivation of forage maize.