Abstract: The aim of this study was to improve the nutritional value of forage ramie by providing optimal selenium (Se) nutrition. The effects of different Se doses on the grass yield and nutritive values of forage ramie were determined using the forage ramie cultivar “Zhongsizhu No1” as the experimental material. The experiments consisted of a pot experiment (1 year) and a field experiment (2 years) with a randomized block design. The doses of applied selenium were 0, 0.25, 0.50, 0.75, and 1.00 kg Se·ha^-1, applied as sodium selenite. We determined nutritive values including crude protein (CP), crude fat (CF), ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), and relative feeding value (RFV), and the contents of Se, phosphorus (P), potassium (K), and calcium (Ca). The results showed that exogenous Se had no significant effect on the grass production of forage ramie. Exogenous Se had some effects on nutritional values, but these effects varied depending on the Se dose, cutting time, and year. In the 2-year field experiment with Se doses of 0.25, 0.50, 0.75, and 1.00 kg Se·ha^-1, on average, crude protein content was increased by 1.52%, 0.96%, -0.10%, and -4.29%, respectively; crude fat content was decreased by 0.25%, 3.93%, 1.54%, and 9.34%, respectively; ADF content was increased by 1.92%, 2.15%, 2.32%, and 3.22%, respectively; crude ash content was increased by 1.37%, 1.23%, 2.29%, and 0.85%, respectively; the change in NDF content was -2.97%, -0.97%, 2.01%, and 2.63% respectively; the change in RFV content was 1.74%, -0.103%, -3.14%, and -4.30% respectively; the change in Ca content was 0.07%, -2.01%, 1.27%, and -0.59%, respectively; the change in P content was 7.26%, 7.68%, 4.63%, and 4.54%, respectively; and the change in K content was 4.59%, 12.31%, -2.04%, and 2.83%, respectively, compared with the control (0 kg Se·ha^-1). The Se content in forage ramie increased with increasing doses of applied Se, reaching a maximum of 2.07 mg·kg^-1. A comprehensive evaluation by principal component analysis combined with the membership function method showed that the range of 0.25-0.50 kg Se·ha^-1 was optimal for Se application in this region to improve the nutritional value of forage ramie.

Key words: selenium, forage ramie, nutrient values, grass yield, comprehensive evaluation